Combined hearing loss is an essential indication for implantable hearing systems. Depending on the bone conduction threshold, various options are available. Patients with mild sensorineural deafness usually benefit from transcutaneous bone conduction implants (BCI), while percutaneous BCI systems are recommended also for moderate hearing loss. For combined hearing losses with moderate and high-grade cochlear hearing loss, active middle ear implants are recommended. For patients with incompatibilities or middle ear surgery, implants are a valuable and proven addition to the therapeutic options.  According to data of the Federal Statistical Office, about 15 million people in Germany suffer from hearing loss, one of five uses a hearing aid Figure 1  [1]. ProBecause of the high complexity of the hearing process, still today the individual treatment of hearing impaired people is a great challenge. Especially in the context of moderate and high-grade hearing loss, conventional hearing aids reach their limits. Based on the S1 guideline entitled “Active implantable hearing systems for hearing losses” , implantThis guideline that is currently in the revision process, the new version is expected to be issued in May 2017. It is generally valid for all patients who cannot be sufficiently supported with conventional hearing aids, whether this is due to medical or audiological reasons. The following indications are defined :Mere sensory hearing disorder reaching the indication range of sound enhancing hearing aidsCombined hearing losses in the context of functional disorders of the middle ear that cannot be treated otherwise by ear surgery with an expected benefit and that are not in the indication range of cochlea implantationsMere conductive hearing lossesMalformations of the ear with one of the above-mentioned types of hearing disorderIncompatibilities of foreign bodies in the auditory canal (e.g. ear moulds)Chronic otitis externa or eczema of the auditory canal or chronic diseases of the outer earIf the above-mentioned indication criteria appear in both ears, a bilateral treatment is indicated. The functional principle of implantable hearing systems consists of transforming the registered sound into electric signals and then into micromechanical vibrations that are transmitted to the ossicular chain or directly into the inner ear. Due to the clearly better amplification, implantable hearing systems do not only provide a better sound quality, but also a more differentiated speech recognition based on less distortion . Also medical reasons such as intolerable occlusion and recurrent inflammations of the auditory canal, social reasons such as the job situation or the patient’s individual preferences may play a fundamental role when deciding in favor of an implantable hearing system. Often a successful social re-integration – job- or private life-related – is the actual clinical “bar” . The impInitially, active middle ear implants were exclusively applied in patients who could not be satisfactorily rehabilitated with conventional hearing aids due to medical reasons. The development of the round window-vibroplasty technique allowed the additional treatment of patients with conductive and combined hearing losses , 6], , , , . The earThe first fully implantable hearing system was the TICA LZ 3001  of the Implex Company that came on the market in 1998. Since 1988, it had been developed in Tübingen by Leysieffer and Zenner. The system was specially conceived for moderate to high-grade sensory hearing loss and led to an improved word recognition and a significant functional hearing gain in several investigations compared to the preoperative, untreated situation.In 1996, Ball developed the Vibrant Soundbridge (VSB), a system that was initially developed by Siemens Company to be produced in series (Symphonix Soundbridge). Later, Med-El Company included the system in their product range and developed the current function. The first implantation was performed in 1996 by Fish in a patient with mere sensory hearing loss. In August 2000, the Vibrant Soundbridge (VSB) was the first FDA approved AMEI for patients with sensorineural hearing loss .In Europe, 3 companies with approved and certified systems are actively present in the market: Med-EL, Otologics, and Envoy Medical Corporation.Journal de Physique in 1783 about “hearing by means of the teeth and part of the hard palate”. In 1821, Itard developed the first bone conduction hearing system, which was a type of megaphone fixed at the patient’s teeth. Finally, in 1925, the first patent was granted for the “Bone Conduct Vibrator”.The idea to use the body’s ability to transmit sound via bone conduction, is rather old. Already in 1757, a doctoral thesis was published by Jorrissen on this topic, written in Latin. It was cited in a contribution to the Via the dentiphone for dentures users in 1939 and glasses with bone conduction function in the 1950ies, basic research was intensified in the 1960ies. The Swedish physician Dr. Branemark introduced the term of “osseointegration”, i.e. the integration of an implant into bony tissue.The breakthrough came in the 1970ies: After the development of a tooth implant with bone conductive function , data ofDuring the last 10 years, miniaturization and digitization led to significant improvements of conventional hearing aids and thus restricted the audiological spectrum of indications for AMEI. Beside medical  and esthetical reasons, the low tolerance of conventional hearing aids regarding humidity is a clearly defined field for the use of implantable hearing systems.The amplified electric signals are transformed into mechanical vibrations and transmitted to the sound conduction apparatus of the middle ear (tympanic membrane and ossicles) or to the cochlea . The necFor the use in active middle ear implants, both systems have specific advantages and disadvantages. Electromagnetic transducers have a higher maximal output amplitude, but they consume more energy for the same acoustic performance. Furthermore, they are not MRI compatible. The piezoelectric transducers are less distorting , but theThe fully implantable system of Carina , excellent sound quality, good quality of life.Disadvantages are the battery charging times and impaired MRI examinations.Indication: The Carina implant is suitable for adults who suffer from moderate to high-grade sensory or combined hearing loss. The patients have to be at least 18 years old. As all electromagnetic transducers, it is not MRI-compatible.Surgical technique: The Carina system is implanted via a postauricular incision (about 2 cm) and fixed at the ossicles . H. HSurgicossicles , 36], . A. AResultpatients . The respatients . Similarpatients , 41], ..Results:The audiological results show consistently a good hearing gain for the Carina system even if long-term results are still not available. Compared to untreated patients, the middle functional gain amounted to 29 dB and 24 dB (p=0.0004) , 38]. T. T38]. THowever, in every published study, also problems with the implant are described. Beside feedback effects that may be met with re-adjustments, those problems include prolonged battery charging times, extrusion of the microphone cable up to complete communication loss of the implanted components and to complete failure of the implant , 35], , .Discussion: In many studies, problems with feedback were reported. Hereby, the position of the microphone under the skin seems to be a crucial factor. Movements of the head and neck may lead to skin displacement that is responsible for disturbing noise. The microphone should be placed in that way that the skin thickness above the microphone remains stable also when head and neck are moved. Also the quality of the intraoperative coupling between the transducer and the ossicles impacts the performance of the implant. The transducer loading assistant software provides intraoperative information on the mechanical load of the ossicles by the transducer and should be applied if possible. By optimizing the coupling, the mechanical displacement of the ossicular chain – and thus stiffening of the ligaments – can be avoided ..DiscussiThe outcome that can be achieved with the Carina system is similar to the one with conventional hearing aids. The fact that many patients prefer implantable hearing systems has no audiological background but is mainly due to the subjectively better quality of life. Clinical long-term data are currently not available. Furthermore, data on the integrity of the incus after manipulation for insertion of the coupling rod are missing. In this context, alternatively possible couplings should be verified.The Esteem system  ossicular chain in cases of atmospheric pressure variations ..SurgicalResults: The results of a first phase-I study with 7 patients was sobering. 4 patients did not benefit from the system because of leaks of the cases; only after revision, 5 patients could be included in the postoperative examinations. The results after 2 months were better compared to the preoperative, untreated condition, but not better than optimal hearing aid fitting.In phase II of the clinical investigations of 2004–2009, the speech recognition threshold was 12 dB higher compared to optimal hearing aid fitting, the average hearing gain amounted to 27 dB, the word recognition was improved by 22% . The subIn 3 patients, secondary facial paresis occurred, 3 other patients had to undergo revision surgery because of insufficient audiological results . FurtherDiscussion: The clinical studies could confirm the desired effects of fully implantable hearing systems. Missing occlusion and low distortions lead to a subjectively better hearing perception than conventional hearing aids. One particularity of the Esteem implant is that the signal registration occurs via the tympanic membrane so that a microphone is not required.However, some disadvantages must be mentioned. Those are among others complex surgeries with obligatory interruption of the ossicular chain to avoid feedback that may lead to additional iatrogenic conductive hearing loss in addition to the existing sensory hearing loss when the device is switched off. Furthermore, the battery can only be changed surgically. The lifetime of the battery mentioned by the manufacturer amounts to 9 years, in practice, however, it is not achieved.The partially implantable Maxum system . After initial difficulties – due to oxidation problems, the magnet had to be changed frequently – the phase I of the clinical studies started in 1998; in 2001, the system was the second FDA approved AMEI. Despite 600 implanted patients, it was withdrawn from the market in 2004 and the technology was taken over by Ototornix in 2009. One of the reasons was probably a rattling noise that was perceived also without audio-processor.Advantages: Easy and rapid intervention that can also be performed under local anesthesia without any problem.Disadvantages: The ossicular chain becomes heavier, often conductive hearing loss cannot be avoided, the ossicular chain has to be interrupted.Indication: The Ototronix Maxum system is suitable for adults with moderate to high-grade sensory hearing loss. As all electromagnetic transducers, the Maxum is not MRI compatible ..IndicatiSurgical technique: The surgical technique can be compared to stapedoplasty and may generally be performed under local anesthesia. After incision and mobilizing the auditory canal flap, the tympanic membrane is tilted and the chorda tympani is neurolyzed. Then the stapes superstructure is exposed.When the implant is inserted, attention must be paid that it is very delicate and must not be touched directly. The open part of the fixation sleeve is placed around the stapes head. It consists of nitinol and can be closed for example with the laser and thus fixed at the stapes head .Results: In 2002, the results of the phase-II study with 103 patients were published . T. TResultublished . Some undesired events were observed in the context of the approval study; those were earaches and a changed gustatory perception. In the context of subjective assessment of complaints by the patients, 55% reported about movements of the magnet that sometimes even required removing the implant .Discussion: It is the case of a simple system that can be inserted rapidly, however, up to now it could not achieve a breakthrough. This is mainly due to the fact that the benefit compared to modern hearing aids is rather low and so the disadvantages strongly overbalance.The MET system .Indications: The Cochlear MET system can be used in adults with moderate to high-grade sensory hearing loss or moderate to high-grade combined hearing loss. The hearing threshold should not be lower than 65 dB HL in the frequencies of 250–550 Hz and 80 dB as of 1000 Hz and be stable. Furthermore, anatomical limitations for the approach to the mastoid antrum must be observed . T. T72]. TDiscussion: Despite the significant surgical efforts and the low number of cases, the results were good to excellent in the first as well as in the second series. In comparison to the TICA, however, the economic base was not considerable so that the system was not widely distributed and finally stopped.The hearing system TICA LZ 3001  the VSB can be brought into contact with the tympanic membrane before surgery in order to give a rough impression of the probable results. The processor technique of the VSB meanwhile contains programs for different hearing situations that the patient may select himself. With more than 50 publications, the VSB is the best investigated AMEI .Advantages: The VSB is MRI compatible up to 1.5 Tesla and may be implanted also in children due to the single-point fixation. Variable coupling options allow the application in various pathologies.Disadvantages: Acoustic shadow in the context of MRI examination of the skull.Indications: The VSB is approved for adults and children from the age of 5 years with conductive and combined hearing losses  as indicator for the quality of life, was used in 4 studies. While the VSB was rated better in the subcategory “general” in all 4 studies, the subcategory “physical” obtained an improvement only in 1 study, in 2 studies the results were comparable, and in 1 the results deteriorated with the VSB .Discussion: The VSB is suitable for different types of hearing loss and is also approved for children . . 121]. TAccording to current experience, the technique can also be applied in children . Skin reThe Ponto system  were frequently observed. A prospective trial with a longer follow-up time should provide information about the long-term benefit.The BCI Best Transducer  . . DiscussThe functional results of Baha and Bonebridge are similar; for the Baha, the amplification of the low frequencies was higher, for the Bonebridge the high frequencies were higher. To improve the significance of those studies, data should be collected over a longer follow-up time.Formerly, the mere sensory hearing loss was the only indication for fully or partially implantable hearing systems. Due to the rapid development of conventional hearing aids, especially the combined hearing loss turned out to be the most relevant indication in the last years. Implantable hearing systems proved their advantage over conventional hearing aids and contributed to a significantly increased quality of life.Depending on the bone conduction threshold, different options are available. Patients with low-grade sensorineural hearing loss generally benefit from transcutaneous BCI while percutaneous BCI systems are more appropriate in the transition to moderate hearing impairment. For combined hearing losses with significant moderate or high-grade cochlear hearing loss, the provision of an AMEI (e.g. Soundbridge Codacs) might be suitable.Despite all progress of the last years in the context of implantable hearing systems, many patients still feel insecure. In comparison to conventional hearing aids, the functional hearing and speech discrimination are only slightly better so that the main application is performed as secondary treatment of patients with incompatibilities or surgeries of the middle ear. Here, implants are a valuable and confirmed addition to the therapeutic inventory.Because of the different fields of application and study designs, the data on the single systems are difficult to compare. For nearly every commercially available product also reports on failure and undesired side effects are found beside convincing outcomes. Further long-term studies are essential to make reliable statements which patients may benefit from which system in the long term.The author received lecture fees and travel expenses from the company MED-EL in the past.


Lead and cadmium have been identified as risk factors for hearing loss in animal studies, but large-scale studies targeting the general human population are rare. This study was conducted to investigate the link between heavy metal concentrations in blood and hearing impairment, using a national population-based survey.The study participants comprised 6409 Koreans aged 20 or older, who were included in the Fifth and Sixth Korea National Health and Nutrition Examination Surveys (KNHANES 2010–2013). Hearing impairment was categorized into two types, low- and high-frequency hearing impairment, using pure tone audiometry. Low-frequency hearing impairment was defined as having a binaural average of hearing thresholds for 0.5, 1, and 2 kHz exceeding 25 dB, and high-frequency hearing impairment was defined as having a binaural average of hearing thresholds for 3, 4, and 6 kHz exceeding 25 dB. The blood levels of heavy metals (lead and cadmium) were classified into quartiles. Cross-sectional association between hearing impairment and the level of heavy metals (lead and cadmium) was examined in both sexes. Multivariate logistic regression was used to obtain adjusted odds ratios (ORs) and 95% confidence intervals (CIs).Among men, the prevalence of low- and high- frequency hearing impairment was 13.9% and 46.7%, respectively, which was higher than the prevalence among women . Regarding lead, the adjusted OR of high-frequency hearing impairment for the highest blood level group versus the lowest group was significant in both men  and women , after adjusting for age, body mass index, education, smoking, alcohol consumption, exercise, diagnosis of diabetes mellitus, hypertension, and noise exposure . No links were found between blood lead levels and low-frequency hearing impairment, or between blood cadmium levels and low- or high-frequency hearing impairment in either sex.The present study findings suggest that even exposure to low-level lead is a risk factor for high-frequency hearing loss. A prospective epidemiologic study should be conducted to identify the causal relationship between human health and exposure to heavy metals, and efforts to reduce heavy metal exposure in the general population should continue. Hearing impairment is one of the most common health conditions, and is increasing in aging societies , 2. AccoHearing impairment tends to increase rapidly with age . Aside fHeavy metals, such as lead and cadmium, are present not only in factory-manufactured products, but also in the environment within air, water, food, soil, and dust –21. InduSeveral studies have examined the relationship between hearing impairment and heavy metals. However, the number of studies on the general population is limited and the number of epidemiologic studies conducted within the Korean population is even fewer. Accordingly, the present study was conducted to investigate the link between exposure to lead and cadmium and hearing impairment using KNHANES data.Data from the fifth and sixth KNHANES, gathered from 2010 to 2013, was used for the analyses. The KNHANES is a multistage stratified complex design survey of a representative sample of the entire Korean population, conducted by the Korea Centers for Disease Control and Prevention. Trained interviewers and laboratory technicians conducted surveys in households, including administering questionnaires, performing health examinations, and collecting blood samples. The section for health behaviors, such as smoking and alcohol consumption, was self-administered. The total number of respondents was 33,552.Of those, 6582 participants aged 20 years or older underwent pure tone audiometry and blood tests to assess the level of heavy metals (lead and cadmium). After excluding those with missing data, a total of 6409 participants were selected as study participants.To examine the respondents hearing condition, pure tone audiometry was performed. Both ears were tested at 0.5, 1, 2, 3, 4, and 6 kHz, in a soundproof booth, using the Entomed SA 203. WHO defines hearing as normal if, in the better hearing ear, the average of hearing thresholds at 0.5, 1, 2, and 4 kHz is under 25 dB , while aTo measure heavy metal blood levels, blood samples were collected into standard commercial evacuated tubes coated with sodium heparin (Vacutainer). Blood lead and cadmium levels were measured via graphite furnace atomic absorption spectrometry . For internal quality assurance, the analytical equipment was controlled with respect to the standard reference material from Whole Blood Metals Control . The blood levels of each heavy metal were classified into quartiles separately for men and women, and geometric means with standard error were computed according to the quartile rank.In the analysis, we included factors suggested by previous studies as affecting hearing impairment. Some studies suggested that cerebro-cardiovascular risk factors, such as obesity and smoking, have a negative effect on hearing ability , 29, bec2 was classified as underweight, BMI between 18.5 and 25 kg/m2 as normal weight, and BMI over 25 kg/m2 as overweight. The education level was categorized as less than high school education; high school graduation; and more than high school education. Cigarette smoking was classified as follows: a non-smoker was defined as never having smoked more than 100 cigarettes; an ex-smoker was defined as having smoked 100 or more cigarettes but currently not smoking; and a current smoker was defined as having smoked 100 or more cigarettes and still currently smoking. Alcohol consumption was defined as: a non-drinker having never consumed alcohol, a light drinker as consuming alcohol less than twice per week or having fewer than 7 glasses (5 glasses for women) when drinking, and a heavy drinker as drinking more than twice per week or having 7 or more glasses (5 glasses for women) when drinking. Participants who performed intense physical activities 3 days or more per week and, with exercise, felt the effects of bodily exertions more than usual, or who performed intense exercises requiring heavy breathing for 30 min or more, were classified into an exercise group, and all others classified into a non-exercise group. Regarding noise exposure, participants who had been exposed to noise at their workplace over a 3-month period or exposed to loud noises such as car horns, machinery, and loud music at places other than the workplace for 5 h or more per week were classified into a noise exposure group. Those who had been exposed to firearm noise were also classified into the noise exposure group. Finally, regarding diabetes and hypertension, participants were categorized into one of two groups, respectively, depending on whether they had been diagnosed with diabetes or hypertension by a physician.Participants’ ages were grouped in 10-year intervals, starting from age 20, and participants aged 70 or higher were collectively gathered as one group. Body mass index (BMI) under 18.5 kg/mp < 0.05. In the first model, age, BMI, education, smoking, alcohol consumption, and exercise were included as adjusting variables, and in the second model, diabetes mellitus, and hypertension were additionally included as adjusting variables. The ORs in the final model were adjusted with exposures to occupational, loud, and firearm noises.Weighted complex sampling analysis available from SPSS v.18.0 was used for data analysis. Regarding the general characteristics of participants, the mean and sample size for each variable was examined by sex. A chi-square test was performed to examine the distributions and t-tests performed to compare means. The relationship between each independent variable and hearing impairment was examined using a chi-square test. This test was conducted separately for low- and high-frequency hearing impairment and by sex. To examine sex-specific relationships between low- and high-frequency hearing impairment and heavy metal levels in blood, odds ratios (OR) were computed using complex sampling logistic regression. Statistical significance was defined as p < 0.001). Additionally, the proportions of those exposed to occupational, loud, and firearm noises were significantly higher in men than in women.Participants totaled 6409, of whom 3185 (49.6%) were men and 3224 (50.4%) were women. The mean age across all participants was 47; the mean age for men was 46, and for women, 48. Table Tables p < 0.001, high frequency: p < 0.001). Focusing on BMI and exercise habits, the prevalence of low-frequency hearing impairment had a lower tendency but not significantly lower in the obese group (p = 0.086) and in the exercise group (p = 0.093). Regarding education level, the prevalence of both low- and high-frequency hearing impairment decreased as the education level advanced (p < 0.001). Low- and high-frequency hearing impairment was less prevalent in the non-smoker group and in the heavy drinker group, as well as in the groups not diagnosed with diabetes and hypertension. In contrast, both low- and high-frequency hearing impairment was significantly more prevalent in the group exposed to occupational noise (p < 0.001). There was no significant difference in the groups exposed to loud and firearm noises.In men, the proportions of low- and high-frequency hearing impairment increased with age . The prevalence of both low- and high-frequency impairment was significantly lower where BMI was lower and the education level was higher, as well as in the heavy drinker group and the groups not diagnosed with diabetes and hypertension. Exposure to loud noise did not show a significant difference, but the group exposed to occupational and firearm noise showed a significantly higher prevalence of high-frequency hearing impairment .In women, the proportions of low- and high-frequency hearing impairment increased with age , after adjusting for age, BMI, education, smoking, alcohol consumption, and exercise. The outcome was the same when diabetes mellitus and hypertension were added as adjusted variables. After adjusting for exposure to occupational, loud, and firearm noises, the ORs significantly increased for all groups, compared to the lowest blood lead group as a reference. Regarding blood cadmium levels, the OR of low- or high-frequency hearing impairment was not significant for any quartile groups, with the lowest group as a reference.As with the men, the ORs of low-frequency hearing impairment were not significant in women for any quartile groups based on blood lead levels, with the lowest group as a reference. However, the OR of high-frequency hearing impairment for the highest quartile group with the lowest as a reference was significant, that is, 1.488 (95% CI = 1.02–2.172), when adjusted for age, BMI, education, smoking, alcohol consumption, and exercise. The result was the same when diabetes mellitus, hypertension, and exposures to occupational, loud, and firearm noises were additionally included as adjusted variables. In addition, in line with findings for the men, women’s ORs for any quartile groups, based on blood cadmium level with the lowest group as a reference, were not significant in either low- or high-frequency hearing impairment.The objective of the present study was to investigate the link between heavy metals to which the general population is generally exposed and hearing impairment. In the study, there was no difference between the sexes in respect of any link between heavy metals and hearing impairment. Regarding the relationship between blood lead level and high-frequency hearing impairment, the risk of hearing impairment significantly increased in both sexes. However, with respect to low-frequency hearing impairment, significant results were not obtained. In addition, blood cadmium level did not show a significant result in either low- or high-frequency hearing impairment in either sex.Several previous studies have reported associations between lead and cadmium levels, and hearing impairment. In a study within the general US population, Choi et al. found that the hearing threshold of the highest quintile groups, based on blood lead and cadmium levels, was higher compared to the respective lowest group, by approximately 18.6% (95% CI = 7.4%–31.1%) and 13.8% (95% CI = 4.6%–23.8%), respectively . Park etAlthough previous studies have shown that heavy metals such as lead and cadmium affect hearing ability, the present study, to the best of our knowledge, is the first epidemiologic study conducted on Korean participants to examine the relationship between hearing impairment and cadmium exposure. The ototoxicity mechanism involving cadmium is suggested by only a handful of studies. In a study with rats exposed to water containing cadmium, it was shown that cadmium produces reactive oxygen species in auditory cells and causes loss of mitochondrial membrane depolarization, release of cytochrome c, activations of apoptosis and caspases, and an increase in extracellular signal-regulated kinase activation that ultimately elevates the hearing threshold , 14. A sRegarding the link between lead and hearing impairment, many studies have reported results similar to the current study findings, unlike the case with cadmium. However, while the mechanisms through which lead influences the auditory system are not yet clearly known, chronic lead exposure is known to be toxic to the central and peripheral nervous systems. By using an auditory brainstem response test, a study has shown that lead exposure affects the conduction function of the peripheral nervous system along the auditory pathways . LikewisThe current study findings support the case that even a low level of lead can negatively affect the hearing condition of the Korean general population and that, therefore, an effort should be made to reduce environmental lead exposure. The fourth quartile groups based on blood lead levels demonstrated a risk for poorer hearing in comparison to the first quartile groups. Currently, the Safety Standards of the Occupational Safety and Health Administration (OSHA) specifies 38.6 μg/dL for lead and 5 μg/L for cadmium as blood level thresholds. None of the 6409 participants in the present study exceeded the recommended threshold for lead, and only 6 exceeded it for cadmium. Accordingly, the current study findings suggest that the risk of hearing impairment is present even at a level below the OSHA threshold recommendation for lead. Evidence has been advanced to demonstrate that even where blood lead and cadmium levels are below the respective recommended threshold, they can still lead to chronic kidney disease, peripheral arterial disease, and hypertension –38. StudAn advantage of the present study is that it was conducted on a representative sample of the Korean population, and the findings can be generalized to the entire Korean population. Although evidence for the link between hearing impairment and heavy metals, such as lead and cadmium, is accumulating, most studies have been limited in that they were either animal studies or based on a small sample size –16. EpidThere are several limitations to this study. First, participants’ past work history was not considered. Secondly, the level of noise exposure was not accurately measured and was based on self-reported data, meaning that information bias could have been present. In addition, the participants might have not accurately recalled their noise exposure history over the course of their lives. Thirdly, information pertaining to additional factors that could affect hearing ability, for example, congenital diseases, middle ear diseases, exposures to physical trauma, medication, and toxic substance history, was not included in the original KNHANES dataset. Fourthly, although the study used secondary data that was representative of the Korean population (KNHANES), it was a cross-sectional study. Hence, a causal relationship between hearing impairment and heavy metals could not be clearly identified.To overcome these limitations in future research, work history, medical history, noise exposure, physical trauma, medication, and toxic substances should be examined and the noise level in the workplace should be measured. Additionally, a cohort study should be conducted that includes people not exposed to occupational and environmental noise.In the Korean population, exposure to low-level lead is significantly associated with high-frequency hearing impairment in both men and women. Therefore, lead exposure should be closely monitored to protect citizens’ health.


Background: Hearing loss is defined as worsening of hearing acuity and is usually expressed as an increase in the hearing threshold. Tinnitus, defined as “ringing in the ear”, is a common and often disturbing accompaniment of hearing loss. Hearing loss and environmental exposures to noise are increasingly recognized health problems. Objectives: The objective was to assess whether the exposure-response relationship can be established between exposures to non-occupational noise and permanent hearing outcomes such as permanent hearing loss and tinnitus. Methods: Information sources: Computer searches of all accessible medical and other databases  were performed and complemented with manual searches. The search was not limited to a particular time span, except for the effects of personal listening devices (PLDs). The latter was limited to the years 2008–June 2015, since previous knowledge was summarized by SCENIHR descriptive systematic review published in 2008. Study eligibility criteria: The inclusion criteria were as follows: the exposure to noise was measured in sound pressure levels (SPLs) and expressed in individual equivalent decibel values , the studies included both exposed and reference groups, the outcome was a permanent health effect, i.e., permanent hearing loss assessed with pure-tone audiometry and/or permanent tinnitus assessed with a questionnaire. The eligibility criteria were evaluated by two independent reviewers. Study appraisal and synthesis methods: The risk of bias was assessed for all of the papers using a template for assessment of quality and the risk of bias. The GRADE  approach was used to assess the overall quality of evidence. Meta-analysis was not possible due to methodological heterogeneity of included studies and the inadequacy of data. Results: Out of 220 references identified, five studies fulfilled the inclusion criteria. All of them were related to the use of PLDs and comprised in total of 1551 teenagers and young adults. Three studies used hearing loss as the outcome and three tinnitus. There was a positive correlation between noise level and hearing loss either at standard or extended high frequencies in all three of the studies on hearing loss. In one study, there was also a positive correlation between the duration of PLD use and hearing loss. There was no association between prolonged listening to loud music through PLDs and tinnitus or the results were contradictory. All of the evidence was of low quality. Limitations: The studies are cross-sectional. No study provides odds ratios of hearing loss by the level of exposure to noise. Conclusions: While using very strict inclusion criteria, there is low quality GRADE evidence that prolonged listening to loud music through PLDs increases the risk of hearing loss and results in worsening standard frequency audiometric thresholds. However, specific threshold analyses focused on stratifying risk according to clearly defined levels of exposure are missing. Future studies are needed to provide actionable guidance for PLDs users. No studies fulfilling the inclusion criteria related to other isolated or combined exposures to environmental noise were identified. According to the World Health Organization (WHO), approximately 5% (or 360 million) of world’ population has a disabling hearing impairment. Exposure to excessive noise is one of the major causes of hearing problems .While the hazards to hearing stemming from exposures to occupational noise are well recognized and appropriate prevention programs have been developed, the risk of hearing loss related to environmental noise or sounds in general population is still not fully recognized.Exposure to excessive noise is associated with damage to the sensory cells of the inner ear (cochlea), predominantly to the outer hair cells . OxidatiIn view of the latest observation in animal models, overexposure to noise may also result in cochlear neuropathy, i.e., the progressive degeneration of auditory nerve fibers, which can develop without permanent damage to the outer hair cells  . Since “EX,8h), or 40 h of working week .The intensity of sounds (noise) is measured in logarithmic decibel (dB) units. The decibel is defined as the logarithm of the ratio between the value of the acoustic pressure of a given sound, measured in Pascals (Pa), and the value of 20 µP, which is the perception threshold . In the logarithmic unit scale, simple addition is not possible. Therefore, a formula of 3 dB exchange rate is commonly used, which means that doubling in sound energy equates to about 3 dB increase of sound pressure level. Major factors determining the development of NIHL are: the intensity of noise , length of exposure (expressed in years), impulsiveness of noise , and individual susceptibility for developing NIHL. The A-weighting is an internationally standardized characteristic in which sensitivity varies with frequency in the same way as the human ear, thus simulating the equal loudness contours. The A-weighting modifies the frequency response to follow approximately the equal loudness curve of 40 phons (high-pass filter). Since the levels of noise vary over time, the level of exposure for assessing the risk of NIHL in occupational setting is calculated as an A-weighted equivalent sound pressure level, averaged over the time of an 8-h working day  action level set at LEX,8h = 85 dBA; and,the second (upper) action level set at LEX,8h = 87 dBA.the maximum exposure limits set at LThe Directive 2003/10/EC of the European Parliament and the Council of 6 February 2003, on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (noise), constitutes the current European legislation regulating the protection of workers from the risk of NIHL . Based oThe limits are to be converted using the time-intensity trade-off of 3 dB increase for halving the time. For example, the exposure to noise at 97 dBA for 30 min a day would equate to the second action level (85 dBA for 8 h), under the assumption of long term exposure . The firTo date, no commonly accepted method for assessing the risk of hearing loss due to environmental exposures to noise has been developed. Thus, the ISO standard and the Directive 2003/10/EC are the main tools used for these purposes.Aeq8h = 85 dB. However, 14% were overexposed and a correlation between the increase of exposure to leisure-noise experienced and tinnitus was observed. Alarming data about health effects comes also from a recent study completed in over 300 British students  AND (“auscultation” [MeSH Terms] OR “auscultation” [All Fields] OR “listening” [All Fields] OR “auditory perception” [MeSH Terms] OR (“auditory” [All Fields] AND “perception” [All Fields]) OR “auditory perception” [All Fields]) AND (“instrumentation” [Subheading] OR “instrumentation” [All Fields] OR “devices” [All Fields] OR “equipment and supplies” [MeSH Terms] OR (“equipment” [All Fields] AND “supplies” [All Fields]) OR “equipment and supplies” [All Fields]) AND (“hearing loss” [MeSH Terms] OR (“hearing” [All Fields] AND “loss” [All Fields]) OR “hearing loss” [All Fields]) AND exposure [All Fields] AND levels [All Fields] AND (“tinnitus” [MeSH Terms] OR “tinnitus” [All Fields])”. The papers identified in this way were analyzed in terms of inclusion criteria. The search was conducted until 30 June 2015, and it was not limited to a particular time span, except for the effects of PLDs. The latter was limited to the years 2008–June 30, 2015, since previous knowledge was summarized by SCENIHR descriptive systematic review published in 2008. Flowchart of assessment of eligible studies in given in Aeq8h), the studies included exposed and reference groups, the outcome was a permanent health effect, i.e., permanent hearing loss assessed with audiometry (or other quantifiable hearing test) or permanent tinnitus assessed with a questionnaire  study design and the number of subjects; (2) age of subjects; (3) exposure assessment; (4) health outcome and the method of measurement; (5) the number (percentage) of subjects with hearing loss/tinnitus; (6) data analysis; (7) main results and conclusions; and (8) the risk of bias of the study.The primary outcome measures were effect-size estimates, such as relative risk (RR) or odds ratio (OR) of permanent hearing loss and tinnitus related to exposure to environmental noise. In the case that the authors of a study provided the prevalence of hearing loss or tinnitus, but not the odds ratio (or relative risk), these values were additionally calculated by the authors of this review by logistic regression (non-linear estimation) with the use of STATISTICA  software. Meta-analysis was not possible due to the methodological heterogeneity of included studies and the inadequacy of data.After excluding duplicates, a total of 220 papers relevant by title to the subject of this study were identified. The inclusion statistics are listed by source of noise in Only five individual studies met the inclusion criteria and all of them were related to PLDs usage. The risk of bias of evaluated papers ranged from high to very high . Two outeq values were taken from the two 32-s measurements [Aeq8h value was calculated based on the estimated level of music and the number of hours a day listening to the music through the PLD declared by an individual in the questionnaire.All five studies are cross-sectional and comprise in total of 1551 participants, including non-exposed controls ,39,40,41urements ,40 or frurements  of musiceq values) had a mean of 72 dB [Aeq8h mean values were 62 dB [Aeq8h [eq(32s), and LEX,8h estimates [Exposure levels  —Low partSulaiman et al. (2013) —The seleLévesque et al. (2010) —No incluVogel et al. (2014) —No direcSulaiman et al. (2014) —No inforThe other risks of bias within studies are as follows:Results of the studies are summarized in Aeq8h values and hearing thresholds at 4 kHz, as well as low frequency pure-tone average at 0.5, 1 and 2 kHz (LFPTA). The individuals with reported use of 1–3 years and more than five years had higher hearing thresholds averaged over 4 and 8 kHz  than the reference group using the PLDs for less than one year. This observation is based on one cross-sectional individual study performed in 237 Canadian teenagers [There is high risk of biased data indicating a positive correlation between individually measured Leenagers . The levAeq8h exposure levels and the incidence of permanent hearing loss assessed by standard pure-tone audiometry, or the occurrence of notched audiograms. However, individually measured LAeq8h values are positively correlated with hearing thresholds at two of the extended high frequencies (11.2 and 14 kHz), but not with the standard frequencies. This observation is based on one cross-sectional individual study performed in 177 Malaysian teenagers [Aeq8h levels of music ranged from 43.0 dBA to 94.0 dBA (mean 61.6 ± 12.9 dBA).There is a high risk of bias data contradicting any significant association between subjects’ Leenagers . LAeq8h Aeq8h exposure levels and their PTA thresholds pooled from 3, 4, and 6 kHz. However, this association was found only in the right ear. Hearing thresholds of PLDs users at extended high frequencies are significantly higher than in non-users. Transient Evoked otoacoustic Emission (TEOAE) and Distortion Product Otoacoustic Emission DPOAE amplitudes in users are significantly reduced when compared with controls (non-PLDs users). This observation is based on one cross-sectional individual study performed in 35 young Malaysian adult PLDs users and an equal number of their age and sex matched controls, which never or rarely used PLDs [Aeq8h levels of music ranged from 57.5 dBA to 89.7 dBA.There is high risk of biased data indicating a significant association between the PLDs usage  and the incidence of hearing loss (defined as hearing thresholds ≥ 25 dB at one or more standard frequencies) and odds ratio of hearing loss see . The consed PLDs . LAeq8h Aeq8h ≤ 80 dBA and the LAeq8h > 80 dBA. However, there is no significant difference in the prevalence of tinnitus when the LAeq8h reference value is set at 85 dBA. When the prevalence values were recalculated into odds ratios by the authors of this review, no difference between differently exposed groups was found. The same was true when the limit was set at 80 dBA and at 85 dBA. This observation is based on one cross-sectional study performed in 124 Canadian teenagers [Aeq8h levels of music ranged from 51.45 dBA to 110.34 dBA (mean 82.59 ± 11.89 dBA).There is very high risk of biased data indicating a significant difference in the prevalence of tinnitus between groups using their PLDs at the Leenagers . LAeq8h Aeq8h ≤ 75 dBA and the LAeq8h > 75 dBA. This observation is based on one cross-sectional study performed in 177 Malaysian teenagers using PLDs for at least six months prior the examination [Aeq8h levels of music ranged from 43.0 dBA to 94.0 dBA.There is a high risk of biased data contradicting any significant difference in prevalence of tinnitus between groups listening to music through PLDs at the Lmination . SimilarAeq56h/week < 80 dBA). This observation is based on one cross-sectional study performed in 1228 Dutch teenagers and young adults [Contrary to expectations, there is a high risk of biased data indicating that students not experiencing permanent hearing-related symptoms (possibly permanent tinnitus) listen to high-risk sound levels of music  2.5 times more often than the reference group   and SulaThe studies included in this report contradict any positive association between the equivalent levels of exposure to music listened to through the PLDs (averaged over 8 h a day or 56 h a week) and the incidence of permanent tinnitus, regardless of the cut-off level applied . Moreover, one of these studies indicates a negative association between listening to loud music through the PLDs at ≥90 dBA and permanent hearing-related symptoms, including permanent tinnitus. Pooled analysis was not performed due to an inadequacy of data. Levesque et al. (2010)  and SulaAeq8h or LAeq56h/week levels of music were calculated based on a single sound pressure level measurement, which was performed in a quiet environment. Thus, the values calculated this way could be encumbered with error due to listener’s changing habits, using different types of devices and earphones, as well as changing the frequency of PLDs usage with high background noise. It has been shown that maximum sound pressure level of music listened through in-ear earphones differ by 14.4 dB depending on the style of music [In all of the studies, the Lof music . The levof music ,42, and of music ,24.According to the ISO 1999 model, the risk of hearing loss and the degree of hearing threshold shift depend on a combination of four major variables: age, sex, equivalent SPL, and years of exposure. In none of the studies included in this review, such comprehensive, combined analysis referring the measured hearing thresholds to those predicted by the ISO 1999 model was performed. The risk of permanent hearing loss was not analyzed separately for men and women.Hearing loss in teenagers and young adults is the resultant value of combined exposures to different sources of noise including, but not limited to, PLDs. Therefore, other sources of music  represent the main bias risk and can additionally account to hearing thresholds shifts in PLD users. This issue was not directly addressed by the studies included in this review.Among all of the sources of environmental noise, exposure to loud music seem to be the most frequent and possibly the most harmful, especially for young people. Up to date, the only data available on exposure-response relationship between exposure to loud music or other types of environmental sounds and permanent hearing outcomes is related to PLDs usage. These studies have been performed mainly in teenagers and young adults.Noise-induced hearing loss develops very slowly over the years of exposure. Thus, the effects of overexposure to loud music could be difficult to single out in teenagers with a relatively short duration of PLDs usage. For example, according to the ISO model, a shift of hearing threshold greater or equal to 25 dB in speech frequencies should not take place in males with healthy ears, provided the exposure to noise does not exceed 15 years for 85 dBA level and six years for 90 dBA level. On the other hand, the dynamics of NIHL development is the greatest in the first years of exposure. For example, the magnitude of NIHL after 3 years is 40% of the NIHL after 45 years. Extended high frequency audiometry and otoacoustic emissions are believed to be more sensitive in the diagnostics of early stages of NIHL than standard audiometry.The literature regarding recreational exposures to loud sounds, including listening to music through PLDs, is quite large. However, the design of a majority of the studies was to measure the levels of exposure and to predict the risk of hearing loss based on international standards, or to measure audiometric and tinnitus outcomes in the PLDs users versus non-users. The combination of both measures (exposure and hearing effect) was less frequent and based mainly on self-reported questionnaire information or in relation to temporary hearing outcomes. Thus, the data on the exposure-response relationship between the exposure to music listened to through PLDs and permanent hearing loss measured by a quantifiable hearing test are very scarce. So far, only three studies of high risk of bias were published by two groups of researchers. The studies were performed in Malaysian and Canadian populations. However very limited, they consistently indicate that exposures to loud music listened to through PLDs may result in hearing threshold shifts, provided the level of music is high and the duration of exposure is long (more than five years). The results of these studies show that if the exposure to music is relatively short (mean 3.2 years), the typical signs of NIHL are not detected in the standard audiometric frequencies 0.25–8 kHz), but can be visible at extended high frequencies –8 kHz, b. Using PIn none of the studies included in this review was a limit of exposure to music established. Some previous literature data indicate that the instance of audiometric notch was considerably higher in young people studying popular music than reported from studies of the general population . On the NIHL is very often accompanied by tinnitus. None of the studies included in this review support the hypothesis that the incidence of permanent tinnitus is positively associated with exposures to loud music. However, in this review the risk of bias of all three studies on tinnitus was high or very high ,25,41. Teq, 8 h of 80 dBA [The data of this review suggests that the OR of permanent hearing loss might be significantly (about four times) higher in regular PLDs users versus non-users. The users are defined as these listening to the music through PLDs for at least 1 h per day, at more than 50% of the maximum volume setting, for at least one year . Similarf 80 dBA , and thef 80 dBA ,49. Thusf 80 dBA .To our knowledge, currently there are no papers meeting the inclusion criteria applied in this work, which would indicate a potential relationship between other environmental noise sources and hearing loss.The literature on the exposure-response relationship between the exposures to environmental noise and permanent hearing outcomes such as hearing loss/tinnitus is limited.As for the PLDs usage, the results of the studies included in this review should be interpreted with caution due to the high risk of bias of the studies, as well as the possible limitations of using the occupational noise standard to predict hearing consequences of relatively short exposures to leisure music.Large-scale case-control studies and longitudinal cohort studies are needed to address the objective of this review in the future. It should be stressed that such studies might be difficult to perform, because the assessment of the average long-term noise exposure appears to be largely impossible due to varying sound levels at different venues and changing individual listening habits over time. Sound levels in different situations and the daily usage of devices may also change, as well as monthly visits of entertainment places and venues. Another limitation is the long time of exposure required for measurable audiometric hearing loss.As it has been shown that temporary threshold shift after exposure to noise might be reasonably predictive of future permanent threshold shift , it woulAn alternative approach to advance the studies on the relationship between exposure to music listened to through PLDs and the risk of permanent hearing loss and tinnitus would be to look at age-related hearing loss progression depending on early age exposures to loud music.While using very strict inclusion criteria, there is low quality GRADE evidence that prolonged listening to loud music through PLDs increases the risk of hearing loss and results in worsening standard frequency audiometric thresholds.Specific threshold analyses focused on risk stratification of permanent hearing loss according to clearly defined levels of exposure to music through the PLDs are missing. This is due to many restrictions of conducting such research that are related to the long latency time from exposure to effect, the problems to correctly estimate the exposure, and the lack of sensitive measures to detect early signs of hearing loss.Available, yet very limited, data contradict any positive association between prolonged listening to loud music through PLDs and the risk of permanent tinnitus. Future studies are needed to provide actionable guidance for PLDs users.No studies fulfilling the inclusion criteria related to other isolated or combined exposures to environmental noise were identified.Since measurable audiometric hearing loss requires long exposure periods and individual dosimetry is preferable to overcome the methodological and practical drawbacks in exposure assessment, such cohort studies would be very challenging.


Background. Korean medicine (KM) patterns such as cold, heat, deficiency, and excess patterns have been associated with alterations of resting metabolic rate (RMR). However, the association of KM patterns with accurately measured body metabolic rate has not been investigated. Methods. Data on cold (CP), heat (HP), spleen-qi deficiency (SQDP), and kidney deficiency (KDP) patterns were extracted by a factor analysis of symptoms experienced by 954 participants. A multiple regression analysis was conducted to determine the association between KM patterns and RMR measured by an indirect calorimeter. Results. The CP and SQDP scores were higher and the HP score was lower in women. The HP and SQDP scores decreased with age, while KDP scores increased with age. A multiple regression analysis revealed that CP and SQDP scores were negatively associated with RMR independently of gender and age, and the CP remained significantly and negatively associated with RMR even after adjustment for fat-free mass. Conclusions. The underlying pathology of CP and SQDP might be associated with the body's metabolic rate. Further studies are needed to investigate the usefulness of RMR measurement in pattern identification and the association of CP and SQDP with metabolic disorders. Resting metabolic rate (RMR) is the amount of energy needed by the body to maintain homeostatic functions during resting conditions. It constitutes the largest fraction of total energy expenditure, accounting for about 65–70% . RMR canPattern identification, also known as syndrome differentiation, is an essential part of diagnosis in Korean medicine (KM). During the process of pattern identification, all symptoms and signs are analyzed to determine the patient's physical condition and the cause, nature, and location of a disease . PatternVarious books and research papers on KM have described the underlying pathology of KM patterns in relation to decreased or increased metabolic rate. For example, a cold pattern and a deficiency pattern are often reported to be related to a lowered body metabolism, while a heat pattern and excess pattern are related to excessive hyperactivity of the body metabolism, suggesting that the symptoms of the KM patterns such as cold/hot sensation in the body, decreased/increased sweating, and clear/red color of urine may be related to the altered body metabolic rate –15.Few studies, however, have investigated the association of KM patterns with accurately measured body metabolic rate. To our knowledge, there was only one study conducted with twelve Japanese women that reported that RMR was lower in women with cold pattern than in women without cold pattern . Thus, tThis cross-sectional study was conducted between 2009 and 2015. The KM symptom questionnaire, RMR, and body composition measurement data were derived from the Korean Medicine Data Center (KDC) of the Korea Institute of Oriental Medicine  Figure . A totalhttps://doi.org/10.1155/2017/9532073). CP was characterized by cold sensation in the feet, cold sensation in the hands, no reddish urine, cold sensation in the abdomen, preference for drinking warm water, and frequent urination; HP was characterized by no aversion to cold, increased sweating, and no preference for drinking warm water; SQDP was characterized by irregular defecation, less frequent bowel movements, feeling of incomplete defecation, indigestion, and fatigue; and KDP was characterized by urination at night, awakening during the night, poor quality of sleep, frequent urination, and loose/watery stool (Supplementary Table S2).Participants were asked to complete the KM symptom questionnaire that consisted of questions about symptoms experienced by the individual within the past 6 months. The symptoms referred to certain conditions, that is, cold/heat, perspiration, defecation, urination, digestion, drinking, sleep, and fatigue, which are deemed important during the basic examination in KM . A factoParticipants were asked to fast and refrain from stimulants  and heavy exercise for at least 12 h prior to visiting the laboratory. RMR was measured with a breath-by-breath gas exchange analysis using an indirect calorimeter . The gas flow calibration as well as oxygen and carbon dioxide analyzer calibration was performed according to the manufacturer's instructions. RMR was measured for 20 min while participants were awake and lying in a supine position. Oxygen uptake and carbon dioxide production were measured and RMR was calculated using the Weir equation .Body height was measured with a digital scale , and weight, fat-free mass (FFM), and body fat mass (BFM) were measured with a bioelectrical impedance analyzer . Body mass index (BMI) was calculated as weight (kg) divided by the square of height (m).t-test. The effect of age on pattern scores was analyzed by a simple regression within each gender. To examine the relationship of the pattern scores and anthropometric and body composition measurements, Pearson's correlation coefficients and partial correlation coefficients controlling for age and gender were estimated. To determine the association between pattern scores and RMR, a multiple regression analysis was conducted; this involved adjustment for age, gender, and FFM, which are known to be an influential factor of RMR [p value of less than 0.05 was considered statistically significant. Statistical analyses were performed using SPSS 22.0  and R .Sample characteristics were presented as the mean and standard deviation, and differences of sample characteristics and pattern scores between genders were compared using an independent r of RMR . A p valp < 0.01). The mean RMR was higher in men  than in women  (p < 0.01).The characteristics of the study participants are shown in p < 0.01), while HP score was lower (p < 0.01) in women than in men. The CP score in women decreased with age (p < 0.05), which was not significant in men (p > 0.05). The SQDP and HP scores significantly decreased with age, while the KDP score increased with age in both genders (p < 0.05) (The CP and SQDP scores were significantly higher ( < 0.05) .In correlation analysis with anthropometric and body composition indices, the CP and SQDP score showed negative correlations with height, weight, BMI, and FFM, while HP showed positive correlations with those indices. When adjusted for gender and age, the correlations of the CP, SQDP, and HP scores with anthropometric and body composition indices became weak but correlations with weight, BMI, and FFM remained significant. The KDP score has no significant correlation with any of the indices .In Model 1, each of the KM pattern scores was entered into the regression model as an independent variable with RMR as a dependent variable. The CP and SQDP scores were negatively associated with RMR, while the HP score was positively associated with RMR. When gender and age were adjusted in Model 2, the CP and SQDP scores were significantly negatively associated with RMR. When additional adjustment of FFM was applied in Model 3, only the CP score was significantly associated with RMR .The present study aimed to investigate the association between KM patterns and RMR. The pattern scores of CP, SQDP, HP, and KDP were different according to gender and age. In addition, CP, SQDP, and HP scores showed significant correlations with anthropometric and body composition indices. A multiple regression analysis revealed that CP and SQDP scores were negatively associated with RMR independently of gender and age, suggesting an association of the underlying pathology of CP and SQDP with altered RMR.CP is one of the eight basic principles of pattern identification and believed to indicate the nature of imbalance in the body. CP is more common in women than in men , 20, andAccording to the KM theory, CP encompasses symptoms of a cold sensation in the body, aversion to cold, lack of thirst, pale facial color, clear urine, and a desire to lie down; thus, its underlying pathology is often associated with decreased metabolism of the whole body –15. A prOne of the possible explanations for the low RMR in individuals with CP could be their low thyroid function , 26, becSeveral studies that investigated the different treatment effects in patients with rheumatoid arthritis found that effects of traditional East Asian medicine or even Western medicine could differ among patients with different characteristics related to the CP , 29. ThiSQDP is mainly characterized by gastrointestinal problems, such as irregular defecation, reduced bowel movement, indigestion, and fatigue. This pattern is defined as a pathological change characterized by qi deficiency with impaired transporting and transforming function of the spleen . GastroiOur results suggest that CP and SQDP were significantly associated with RMR after adjustment for gender and age. This means that RMR is different according to the status of CP and SQDP in individuals with the same gender and age. Even though FFM is known to be the most influential determinant of RMR, FFM should be measured with a device such as a bioelectrical impedance analyzer or a dual-energy X-ray absorptiometer. Accordingly, the results indicate that evaluating CP and SQDP could be helpful to predict RMR of patients in a more practical way in clinical settings. Moreover, the CP was negatively associated with RMR after additional adjustment for FFM. Thus, consideration of the CP is recommended even when estimating an individual's RMR based on his/her FFM value.The KM diagnostic process has been criticized for its subjectivity and dependence on the doctor's experience; thus the need to establish standardized diagnostic method using objective and quantitative methods has been asserted in the literature , 34. BecOur results showed that the HP score was higher in men and showed positive associations with weight, BMI, FFM, and BFM and negative association with RMR, which was the opposite of CP. However, unlike the CP, the association of the HP with RMR was not significant after adjusting for gender and age. This is possibly due to the different composition of the symptom characteristics that are related to HP and CP in our study. The CP in our study was extracted by a factor analysis and mostly constituted symptoms related to thermal sensation of the body, while the HP mostly constituted symptoms related to preferred ambient temperature or sweating amount. However, according to KM theory, CP and HP are basically two patterns that reflect the nature of imbalance in the body and indicate the relative exuberance and debility of the yin and yang of the body. Consequently, the manifestations are conceptually contrast to each other; for example, the CP includes the symptoms of aversion to cold, preference for warmth, and a pale face, while the HP includes the symptoms of aversion to heat, preference for coolness, and a red face. Based on our results, it seems that the symptoms that are known to be relevant to the CP and HP are not necessarily analyzed as just one pattern. Our results could be interpreted as that the symptom pattern that was mostly about thermal sensation in the direction of cold was significantly associated with RMR and the symptom pattern that was mostly about preference for ambient temperature and sweating amount in the direction of heat were not significantly associated with RMR.KDP is characterized by urination at night and sleep problems of awakening during the night and poor quality of sleep. The KDP score showed a significant increase with age, which is consistent with the KM theory that kidney function deteriorates with age . The KDPAlthough there were studies that utilized a factor analysis of symptoms to statistically identify KM patterns , 29, 36,Some caution is needed when interpreting the results of this study. Firstly, data of healthy participants were analyzed in the study instead of patients with a specific disease. We expect symptoms related to KM patterns to be more prevalent and severe in patients with diseases and future studies to investigate the associations of KM patterns with RMR in various disease groups are required. Secondly, symptoms used in this study were self-reported, based on recall over the previous 6 months. Although self-administered questionnaires on symptoms have been widely used to evaluate an individual's health –42, thisOur results showed that the individuals with higher CP and SQDP scores have lower RMR when compared to individuals of the same gender and age with lower CP and SQDP scores, suggesting that the underlying pathology of CP and SQDP may be associated with the body's metabolic rate. In consideration of the effect of altered RMR on metabolic disorders, evaluating the CP and SQDP in patients with metabolic disorders is recommended. In addition, to complement the subjectivity of the current KM diagnosis process, further studies are required to investigate the usefulness of RMR measurement in CP and SQDP pattern identification.The Supplementary Material describes the detailed process of identifying symptom patterns, including the symptom questionnaire, the methods and results of factor analysis, and the comparison of factors extracted by factor analysis with KM patterns in the literature.


Hearing Aids amplify sounds at certain frequencies to help patients, who have hearing loss, to improve the quality of life. Variables affecting hearing improvement include the characteristics of the patients’ hearing loss, the characteristics of the hearing aids, and the characteristics of the frequencies. Although the two former characteristics have been studied, there are only limited studies predicting hearing gain, after wearing Hearing Aids, with utilizing all three characteristics. Therefore, we propose a new machine learning algorithm that can present the degree of hearing improvement expected from the wearing of hearing aids.The proposed algorithm consists of cascade structure, recurrent structure and deep network structure. For cascade structure, it reflects correlations between frequency bands. For recurrent structure, output variables in one particular network of frequency bands are reused as input variables for other networks. Furthermore, it is of deep network structure with many hidden layers. We denote such networks as cascade recurring deep network where training consists of two phases; cascade phase and tuning phase.When applied to medical records of 2,182 patients treated for hearing loss, the proposed algorithm reduced the error rate by 58% from the other neural networks.The proposed algorithm is a novel algorithm that can be utilized for signal or sequential data. Clinically, the proposed algorithm can serve as a medical assistance tool that fulfill the patients’ satisfaction. As individuals have longer life expectancies, the quality of life has become more and more important nowadays as well as auditory rehabilitation of hearing impaired persons. In the recent years, the need of hearing aid(HA)s for patients with hearing loss is spreading widely however, the satisfaction levels of HAs are quite diverse among individuals. One of the many causes that affect the satisfaction levels is the composite interactions between the variables that affect the outcomes of HAs. Walden et al  investigFor successful use of HAs, a highly reliable prediction model attributing to specific characteristics of HAs and frequencies is essential. Although there are algorithms for fitting of HAs developed by various HA manufacturing companies, objective information on the degree of hearing improvement obtained by different HAs in patients are sometimes inaccurate or concealed. Mulrow et al.  proposedFigure Therefore, the purpose of this study was to develop a new model that can present the expected degrees of hearing gain followed by HA fitting based on the variables that can affect the outcomes of HAs. This model is expected to fulfill the patients’ expectation levels, motivate the patients to use and manage HAs, and help to maximize the hearing improvement through application of HAs in the clinical fields.n instances, x = {xi | xi ∈ Rd, i = 1, 2, …, n} and k target variables, y = {yj | yj ∈ R, j = 1, 2, …, k}, the learning process of a neural network is to estimate the weight w that connects each nodes. The estimation of w is calculated in the direction of reducing the error, which is the difference between output variable f = {fj |fj ∈ R, j = 1, 2, …, k} and target variable y. Thus, the objective is to minimize the sum of squared errors and the optimization problem is:The proposed algorithm is based on neural networks. Neural networks are machine learning algorithms used for prediction or classification. It is known to show high prediction performance even in cases where the relationships between input variables and target variables have not been defined or are complicated . Out of In this study, we propose a novel neural network that have three structural characteristics: cascade, recurrent, and deep network structure. Previous studies concerning each of the three structures are reviewed as the following.When a neural network obtains high prediction performance, selecting an appropriate number of hidden nodes is important. Although the number of hidden nodes is selected by trial-and-error, in general, there has been extensive studies in determining the number of hidden nodes through algorithm. One of the representative algorithms is a cascade-correlation neural network which selects the optimal number of hidden nodes by adding a single hidden node at each step in the training process. In addition, it achieves faster training process than general neural networks , 10.k target variables, y = , that has characteristics of time-series, the output variables are correlated with each other. In such case, higher performance can be obtained by utilizing previous step yt-1 as an input variable for prediction of t-time step yt. This is well consistent with the concept of Recurrent Neural Network that combines a general neural network with the notion of time series. In recurrent neural network, hidden nodes are utilized as storages that preserve the information in previous training step  = net1(w(0), x(1), y1) where w1) =  is input vector for predicting y1. When the neural network net1 has been sufficiently trained, we construct neural network net2 that predicts y2. For training net2, the output value f1 is added to input vector x. Since the two target variables y1 and y2 affect each other, weight matrix w1)] = net2(w(1), x(2), y2) where w2) =  is input vector for predicting y2. Then, neural networks for the remaining output variable are learned in the same manner. In general, the final predicted value fk is calculated byInclining step is a process where output variables are learned progressively. When we have wk)th neural network. Since every output variable accompany errors the input variable fk contains errors that must be corrected. It is known that error-correction networks can improve prediction performance in deep neural networks -[Hidden Layer]-[Output Layer]) having 31 input nodes, 20 ~ 30 hidden nodes on average, and one output node [netHz250 for predicting frequency band of 250Hz is sufficiently trained. Then, network netHz500 for predicting frequency band of 500Hz utilizes netHz250 as a base learner. For training net500Hz, the output variable fHz250 of net250Hz is utilized as an input variable and the weight wHz) where smaller values imply higher prediction performance [To compare the prediction performance of the proposed algorithm that reflect correlations between frequencies, a neural network in the structure as shown in Fig. put node . In otheformance . MAPE isyi is target values, fi is output values.where, n is the number of entire data, 1, and MLP6) by frequency bands. CRDN shows the lowest error rates in all frequency bands (Avg. 9.2%). On the contrary, six MLP1s and MLP6 showed error rates of 21.8 and 16.8% on average respectively. We could deduce that CRDN, which reflects every correlation between target variables, shows highest performance, followed by MLP6, which can reflect some proportion of correlations between target variables. In addition, the error rates of inclining and declining in CRDN are 13.1 and 10.7% on average respectively. If we compare the error rate of CRDN (Avg. 9.2%) that had been trained up to the last step, tuning phase, we could deduce that considering adjacent frequencies more often leads to improvement in performance.Figure The low error rate of CRDN has meaningful implications in clinical aspects. Since hearing tests only select representative frequency bands, it is difficult to measure the actual thresholds in PTA of adjacent frequency bands. It only approximates the thresholds with median of measured PTA of adjacent frequency bands. For instance, a 4 K-dip from noise-induced hearing loss not only has high thresholds in PTA for 4KHz but also affects adjacent frequency bands. Since CRDN structure considers such influence, it is bound for successful results.To verify the utility of CRDN, the proposed algorithm was applied to actual patients. We show cases of patients with sensorineural hearing loss and patients with conductive hearing loss. Figure Figure For convex type, the threshold of medium frequencies is higher than that of low frequencies and high frequencies by at least 15 dB. In such cases, the patients with hearing loss cannot hear the sounds of daily conversations. To resolve the hearing loss, we applied CRDN to patients with sensorineural hearing loss. The expected degrees of hearing gains with CRDN was fitted with actual hearing gain, and the results show high satisfaction levels.Figure Although the patients have different characteristics of hearing loss, patient information and clinical evaluations for both cases, CRDN can provide suitable hearing gains for individual patients. On the basis of results, CRDN can serve as a medical assistance tool that fulfill the patients’ satisfaction levels, and helps to maximize the hearing improvement through application of HAs in the clinical fields.In this study, we propose a novel neural network algorithm that provides expected degrees of hearing gain for patients with hearing loss who wear hearing aids. The proposed algorithm is a Cascade Recurring Deep Network that reflects correlations between adjacent frequencies. This is a deep network that piles up same number of hidden layers as that of target variables such that it can be utilized for signal or sequential data. Also, it takes the structural advantages of cascade-correlation networks and recurrent neural networks.In algorithmic perspective, CRDN has novelty in following aspects. CRDN has a scalable structure that can be applied to various signal or sequential data, and achieves faster training time since it progressively piles up the layers. CRDN reuses neural networks that previously have been trained and it not only achieves fast training time but also reflects the correlations between output variables. In addition, since CRDN uses weights that previously have been learned, it can reduce the time of learning weights in predicting new output variables. In the experiments, the mean error rate of CRDN in six frequency bands  was 9.2%. When compared to other neural network models that does not reflect correlations between frequencies, it showed that the mean error rate can be reduced by 58%. In this paper, we only compared performance of CRDN with two types of MLP. As an extension of the comparison, we can consider other machine learning algorithms such as support vector machine, regularized regression analysis, etc.In clinical perspective, since CRDN provides more accurate information on expected hearing gain after wearing hearing aids, it can reduce the gap between expected and actual experience of wearing hearing aids. Therefore, it can serve as an effective medical assistance tool. Further works include applying the proposed algorithm to other types of signal or sequential data.


The interest towards research in hearing loss and ear disease has seen a great and progressive increase in the light of the continuous increase in the number of challenging research articles. Although hearing loss is a worldwide health problem and its socioeconomic burden is globally significant, nonregenerative hair cells in the cochlea and difficult drug delivery to the inner ear hindered progress in the field of hearing recovery . HoweverThis special issue brings together 10 research articles and review article which nicely illustrate the wide spectrum of basic inner ear research and its related research about central auditory pathway. While some cutting-edge researches about neuroimaging study of central pathway including auditory cortex and higher cognitive function were illustrated, basic inner ear studies using many kinds of animal models were also described. In detail, diabetic mice, gerbil hearing loss model with aminoglycoside administration, and specifically devised early progressive hearing loss model were introduced. This special issue also includes deriving significant clinical implication, predicting the surgical outcomes from the data of cochlear implant recipients. Finally, the art of nanomedicine was thoroughly reviewed in the field of inner ear research.The collection of papers published in this special issue nicely covers all the fields of hearing science including basic molecular study, imaging study, and clinical implication study and we hope that it will attract the interests of a large number of basic researchers as well as clinicians aiming at improving the treatment of hearing loss.Yong-Ho ParkSung K. MoonKenneth H. LeeJeong-Han Lee


Hearing loss remains a neglected public health issue in the rural and agricultural communities in the United States and therefore, promotion of a low-cost hearing screening may be important for these underserved populations. The major objectives of our study were to assess feasibility of a low-cost telephone-administered hearing test in rural Indiana and to identify the challenges, barriers and viable implementation strategies associated with this test. Also, we evaluated whether a focus group session could change the hearing health attitude of rural residents.We recruited 126 adults from six rural Indiana counties who participated in study activities in the following order: 1) a pre-focus group demographic, knowledge and attitude survey, 2) a focus group for discussing the feasibility of a telephone-administered hearing screening, 3) a post focus group attitude survey and 4) hearing was screened using an audiometer and self-assessment scale. These activities generated both qualitative and quantitative data, which were subsequently analyzed.Hearing impairment was perceived as an important public health issue. Many participants expressed interests to try the low-cost National Hearing Test (NHT). However, participants recommended NHT to be facilitated by community organizations to provide access to landline phones. The focus group turned out to be an excellent awareness building activity producing significant improvement in hearing health attitudes. Comparison of self and audiometric evaluations indicated underestimation of hearing handicap in our rural study population.The study results underscore the urgent need for an effective strategy to promote low-cost hearing screening in rural US communities. Adult hearing loss in the United States remains neglected as a public health issue . In addiWhile current literature has emphasized the prevalence of hearing loss in urban areas, it remains an equally significant problem in rural communities. Age-related hearing loss is common among all types of populations and NIHL has been associated with occupational noise exposure particularly among rural farmers . Most ocImplementation of hearing screening programs in rural areas may be extremely challenging due to persisting health disparity issues. One of the main issues is lack of funding for health programs. Residents of rural communities earn less on average than those in urban communities and pay less in tax dollars, while the local public health officials have fewer resources to draw on for funding health related programs . IndividLow-cost telephone administered screening tests utilizing three-digit sequencing presented in noise have been developed, validated and implemented in seven countries. Each of these tests have been based on a test protocol conceived by Smits and colleagues in the Netherlands . More reIn order to address the use of a low-cost hearing screening test and hearing health in rural communities, we addressed several specific aims in this study. The first aim of the study was to assess the acceptability of a low-cost hearing screening test. In order to evaluate the feasibility of the test, we asked the participants questions about the following: 1) how important hearing is in rural communities, 2) if they are willing to take the test, 3) identifying the best mechanism in which the test can be implemented across rural communities, 4) barriers and obstacles to the test and taking the test, and 5) evaluation of the test by the test takers. The second aim of the study was to determine whether the discussion and education on hearing health could have a short term impact on attitude towards hearing health. The third aim of the study was to evaluate whether hearing health knowledge levels are different between the general population and those exposed to loud noise through their occupation. The last aim was to examine the correlation of three different hearing screening tests .The study was conducted in six counties of southern Indiana with the help of Indiana Rural Health Association (IRHA) who have long-standing collaborations with many community organizations such as community service centers, churches, hospitals and clinics located in rural Indiana. An initial list of 10 counties of southern Indiana was generated by the staff of IRHA who assisted the researchers of Indiana University-Bloomington School of Public Health (IUB-SPH) to recruit study participants. Counties in this list met the following criteria to be considered as a unit of the study area: 1) had one or more rural community organization (RCO) that previously partnered with IRHA in a public health project, 2) the partner community organization had contact information of at least 50 local residents including individuals who had a history of working in noisy environment (e.g. farmers) in their lifetime, and 3) the facility that the partner organization was able to provide for the study would include separate rooms to concurrently conduct focus group and hearing screening sessions. Six counties Daviess, Greene, Lawrence, Orange, Owen and Sullivan were randomly selected from the initial list for recruiting participants. The study was approved by Indiana University Human Subjects Office, which is the administrative office that supports the Indiana University Institutional Review Boards (IRB) in April 2015.In the spring of 2015, IRHA staff communicated with RCO and finalized a date for each county to conduct all necessary study activities. Subsequently, an RCO representative contacted the potential participants, checked his/her availability and eligibility, and then briefly described the study procedure. Recruitment announcement was posted in the RCO’s notice board at least 7 days prior to the study session. Additionally, the RCO representative made a direct phone call to a potential participant whenever a contact phone number was available. IRHA and RCO staff jointly maintained a list of potential participants who initially responded positively to participate in the study session and gave them a reminder about the schedule of the study activities 48 h before the study session. On the day of the study session, written informed consent was obtained from 126 adult participant from the six counties by the researchers from IUB-SPH. Study activities started with a short demographic survey questionnaire that was filled out by the participant. This was used to collect information about age, sex, ethnicity, occupation, income, housing status, history of occupational noise exposure, history of hearing screening and evaluation of hearing health status by an audiologists and use of hearing aids. This was followed by several other data and information collection activities as per the specific aims of the study: 1) short hearing knowledge questionnaire, 2) a pre-focus group attitude questionnaire, 3) focus group on the feasibility of a telephone hearing screening test, 4) self-evaluation of hearing of the participant using a questionnaire, 5) a post-focus group attitude test, and 6) an audiometric screening of hearing. All participants also received necessary information (including an access phone number and an access code) to participate in the telephone hearing screening known as the National Hearing Test (NHT) using a landline phone within 2 weeks of the study session.Participants filled out a 15-item hearing health knowledge questionnaire with each question presenting two possible responses: “TRUE” and “FALSE”. Questions were adapted from a hearing health public awareness publication from the World Health organization (WHO)  and a heA 15-item attitude and belief questionnaire was adapted from a health belief model-based questionnaire, which was found to be a valid tool for assessing attitude in a previous US study . Each itAll participants completed a 10-item screening version of the Hearing Handicap Inventory for Adults (HHIA-S) . Five itPure-tone air conduction screening was conducted by a study research assistant who was trained by an audiologist. All screenings were conducted in a quiet, private room with limited external influences . Screening was performed on both left and right ears using the Beltone 10D portable audiometer at the frequencies of 500, 1000, 2000, and 4000 Hz at a level of 25 dB HL. The participant was instructed to respond positively by raising their hand each time they heard the tone. If a participant had one “no response” at any frequency in either ear they “failed” the screening and were subsequently advised to visit an audiologist for additional hearing evaluation.The purpose of the focus groups was to explore hearing health related attitudes and beliefs of adults living in rural Indiana, including both those who have been exposed to loud noises from occupational activities and those who have not. In addition, perceptions about the NHT were examined in order to assess use and identify possible organizations or groups to administer it.An interview guide was developed to elicit attitudes and beliefs about the importance of hearing in comparison to other aspects of health; assess good, bad, easy, and difficult aspects of getting a hearing test; and explore willingness to participate in a telephone hearing test. A member of the research team moderated each focus group.A total of six focus groups were conducted with farmers and non-farmers residing in rural communities. Five focus group sessions were audiotaped and transcribed; one group was not taped due to equipment failure. Participants’ names were not included in the transcripts to maintain confidentiality. For this reason, frequencies for statements and opinions made in the groups were not calculated.Qualitative data analysis was conducted using Dedoose software version 7.1. A member of the team reviewed transcripts. Descriptive and in vivo coding were used to summarize a word or a phrase capturing participants’ feelings and attitudes about hearing and taking hearing tests as well as factors that prompt or hinder promotion of hearing health in rural communities. Codes were grouped into categories. Analytic/memo writing was as a technique used to make connections between categories and to further identify patterns and themes.t-test for continuous variables. To indicate internal consistency and reliability of the attitude items in the questionnaire, we calculated Cronbach’s alpha for pre and post attitude scales separately. Participants received 1 point for each correct answer in the knowledge questionnaire. Points were then added up to compute a summary knowledge score. Pre- and post-attitude summary scores were also calculated by adding points  for each of the 15 items. A paired t-test was used to examine the difference between pre- and post-focus group attitude scores to examine if the attitude changed significantly within each group of participants.Quantitative data analysis was conducted using SPSS® 24. Study participants were divided into two groups: the first group with no history of significant occupational noise exposure and the other group with history of occupational noise exposure. The two groups were then compared for the differences in sociodemographic characteristics using chi-squared test for categorical variables and independent sample All participants, aged 25 and over, were recruited from rural communities located in six counties  of the state of Indiana. Participants who reported high-noise exposure in their present or any previous job (i.e. those who worked at jobs that involved noisy tasks or jobs for which hearing protection was recommended) were classified as “potential occupational noise exposure,” whereas those who did not work in such environment were classified as “no occupational noise exposure”. The potential noise exposure group was significantly older, had significantly higher proportion of males and lower level of education than the group consisting of participants with no history of occupational noise exposure Table . The majThe major finding from the focus group sessions are presented in Table I think there are more people wearing [hearing aids] now than they use it because they are handier…and as far as the expense…I don’t think it is the expense of the hearing test. It is the experience of the hearing aid. If you do find out that you loss…[your hearing].Participants mentioned that individuals may not want to accept that there may be a problem. It is easy to ignore. One participant stated:Some individuals in the focus group noted that they noticed certain signs such as ringing in the ear. Most of the time, a spouse, friend, or co-worker suggested that they go get a hearing test. Few followed up on the recommendations while others failed to do so.Most individuals shared positive, but mixed feelings about taking the NHT. A few individuals felt that the NHT should be directly towards a younger population, specifically middle and high school students. Additionally, a number of older participants felt loud music played through earphones or through the speakers of a vehicle were more of a concern and could be quickly remedied using the NHT.I think [name of focus group participant voicing important of education] is right about pushing it through education. Prior to coming here, I still would have ….continued to not use hearing protection for certain things like doing hunting….The focus groups not only assisted researchers’ answer specific study aims, they also served as a health awareness intervention for the majority of participants. Personal stories were shared among participants about hearing tests, hearing aids, recreational noise exposure, and community norms and expectations of hearing. One participant mentioned:I think they need to do public service announcements like they do for smokin’. On television. Cuz people…we can tell them and it won’t do any good, but we need somebody to tell them about noise…what to listen to…why they can’t hear….especially like for they do for people who are smokin’.Although this participant works in an environment where exposure to noise is low, the discussion encouraged her to think about spaces where she is exposed to higher levels of noise. Recreational activities, such as motor biking, sports shooting, concerts, and hunting were discussed as spaces where hearing protection is needed. The focus group discussion prompted her to revisit their own beliefs. In addition, the focus groups prompted potential health strategies to raise awareness about hearing health. Public health awareness was most frequently cited. One participant stated:Other strategies included enforcement of workplace policies to encourage use of hearing protection and health education and science curricula in schools.t = 1.34, P = 0.03) and without occupational noise exposure  . The attitude scale used in the study was found to be extremely reliable as we observed high Cronbach’s alpha values for both pre (Chronbach’s α = 0.79) and post (Chronbach’s α = 0.89) attitude and belief questionnaire. The mean attitude score for the entire sample (n = 126) increased from 3.64 (SD 0.46) to 3.83 (SD 0.59).The mean hearing attitude scores significantly increased after the participation in the focus group among participants with occupational noise exposure . The no occupational noise exposure group has a significantly higher knowledge score (71.3% ± 21.4%) than the potential occupational noise exposure group (62.2% ± 21.1%).There was a significant difference for knowledge scores (mean % correct) between the participants with potential occupational and no occupational noise exposure (p = 0.03)  than the group with potential occupational noise exposure in their lifetime (22%)  completed the low-cost NHT within 2 weeks of the focus group and two other hearing screening events. Participants who had potential occupational noise exposure had higher NHT participation rate compared to those who had no occupational noise exposure history (27.1% vs 20.9%).Out of 126 participants, only 23.8%  in the group with no occupational noise exposure. This may be attributable to a difference in perceived hearing between groups as individuals with a history of occupational noise exposure tend to consider hearing loss as a natural and unavoidable health consequence in later stages of life . We do nP < 0.001) with the highest correlation observed at 2000 Hz [There are several limitations of the study. The study did not capture information about past recreational noise exposure such as recreational firearm use, which was shown to be associated with hearing loss . Informa 2000 Hz .Our study was conducted in Indiana, where around 14% and 24% of the population resided in the rural counties and semi-rural counties according the 2010 census . In geneWhile the NHT is a valuable resource to offer low-cost hearing screening in rural communities, there are several potential barriers that need to be addressed. The NHT was developed to be administered via landline telephone , 22 and Our study indicated that adults in rural Indiana perceived hearing loss as an important public health challenge for rural populations and were enthusiastic to take the low-cost telephone-based National Hearing Test (NHT). However, due to the lack of landline phone access in a majority of the households our study participants suggested that community organizations could play the role of trusted facilitators by providing the logistics required for this screening. Results from the focus groups and other formats of hearing screening (e.g. questionnaire and audiometric screening) reflect the fact that in spite of the ignorance and underestimation of the hearing health issues in our study areas, education and awareness building activities coupled with the low-cost NHT could bring marked improvement in hearing health status of rural US populations.