, urinary incontinence ( ui ) affects about one third of healthy elderly people , and up to 90% of nursing home patients . the proportion of the elderly population is increasing worldwide ; it is currently around 10% , and is expected to reach 20% within 40 years . accordingly
, the prevalence of conditions such as metabolic syndrome and obesity are increasing annually , and these are key risk factors for voiding dysfunction .
moreover , voiding dysfunction influences patient quality of life , and can contribute to serious morbidities , such as falls and bone fractures .
the average age of the south korean population is increasing more rapidly than that in other countries : the proportion of elderly people rose from 3.8% in 1980 to 9.5% in 2006 .
consequently , south korean society is becoming more concerned over voiding problems after middle age .
for this reason , it is essential that investigators conduct epidemiologic studies into the prevalence of voiding dysfunctions in south korea . in this review
, we aimed to clarify the prevalence and clinical features of voiding dysfunctions among both men and women .
several extensive epidemiologic studies have been performed in western countries since the 1990s ; however , in south korea , epidemiologic studies have only been conducted since the start of the 21st century . to advance epidemiologic research ,
longitudinal designs confer greater statistical power than cross - sectional designs , because longitudinal research uses serial data that reveal substantial realistic prevalences , as well as the potential causes of the disease . on the other hand ,
more epidemiologic studies involve a cross - sectional design . to ensure significant epidemiologic data , investigators must select a proper target population and adopt proper survey methods ; questionnaires should be adjusted to the target population .
early epidemiologic studies into voiding dysfunction were mainly performed by postal survey ; this method has been commonly used since the 1960s .
this approach involves lower costs and higher efficiency , and it has fewer effects on the patients mood ; therefore , the postal survey served as a strong epidemiologic method .
more recently , communication devices and multimedia technology have allowed telephone interviews and internet surveys to emerge as practical epidemiologic tools .
telephone interviews can provide a cross section of almost the entire population , and they are cost- and time - effective . furthermore , the results of telephone interviews are less influenced by the interviewer than are those of personal interviews . nonetheless , this method is limited , because , in the past , few people in south korea had telephones . with the increased distribution of telephones ,
, the telephone interview can be affected by social desirability bias , which can arise in cases of delicate personal questions , especially in the field of urology .
furthermore , some people feel their privacy is violated by random - dialing surveys ; therefore , the nonresponse rate increases .
after high - level communication and multimedia technology were developed , the internet survey was introduced to gather data .
however , such an approach confers a coverage problem , because most people are still not capable of accessing surveys via the internet or electrical devices . for this reason
, the internet survey must be developed further if it is to become the ideal survey design .
in addition , internet surveys require comprehensive programming , which is not true of face - to - face interviews . therefore , the face - to - face interview is still frequently used in epidemiologic studies , even though more money , time , and manpower are required .
the major advantage of the personal interview is that the researcher can explain the intent and exact meaning of questions ; this guarantees higher response quality .
it is true that every survey method has its own advantages and handicaps , and sometimes various survey methods are used concurrently .
nonetheless , large - scale epidemiologic data are most frequently obtained by telephone interview or internet survey .
furthermore , in both sexes , ui , lower urinary tract symptoms ( luts ) , overactive bladder ( oab ) , and nocturia are highly prevalent , distressing conditions .
herein , we have provided an overview of the epidemiologic studies into the above voiding dysfunctions in south korea .
all of the surveys included in this review were conducted after profound consideration of the various aspects .
furthermore , we have reviewed in detail each specific survey method , as well as the methods for obtaining detailed clinical details of voiding dysfunction .
finally , we considered the practical limitations of the survey selection processes , which are influenced by special factors .
its various voiding - related symptoms , enhanced by obstruction of the bladder outlet , include nocturia , tenesmus , urgency , and hesitancy ; these symptoms reduce the quality of life in affected men .
the prevalence of bph increases with age , and it affects 40% to 70% of men aged between 60 and 70 years .
bph is diagnosed pathologically in approximately 40% of autopsies of men in their 50s , and in 70% of autopsies of men in their 60s .
hence , in this review , we have used based based definitions of bph as a voiding dysfunction . to investigate the real prevalence of bph
the demarcation of what constitutes clinical bph is somewhat controversial ; to date , clinicians have come to no consensus regarding the definition of bph .
in addition , different characteristics of the target population , as well as the methods used to collect information , can influence the results .
this diversity in the definition of bph influences the ability of investigators to analyze and compare results across studies .
the first study into bph prevalence in the inland area of chungcheongbuk - do was performed in 1999 , and 27.7% of 764 men were found to be affected . in this study ,
bph was defined when the prostate volume ( pv ) , measured by transrectal sonography , was 20 ml , and when the maximal flow rate ( qmax ) was 10 ml / sec . in another study
, bph was defined when the international prostate symptom score ( ipss ) was 8 , when the pv ( measured by finger ) was 30 ml , and when qmax was 15 ml / sec .
the rate of moderate - to - severe ipss was 49.5% ( 213 in 431 men ) .
but by the definitions in this study , bph prevalence were 4.3% of men in their 50s , 13.2% of men in their 60s , and 16.3% of men in their 70s or older ( overall , 11.1% of men aged over 50 years ) .
the population - adjusted prevalence of bph in south korean men aged 50 and over was 8.7% .
another community - based study defined bph in cases of an ipss 8 points and a qmax 10 ml / sec ; the study found that the incidence of bph was 25.5% . on the basis of ipss , 36.3% , 49.7% , and 14.0% of the men were mildly ( 17 ) , moderately ( 819 ) , and severely ( 2035 ) symptomatic , respectively .
in 2009 , park et al .   found that the prevalence of bph , defined in cases of an ipss > 7 and a pv > 30 ml , was 40% .
this study was based on the korean longitudinal study on health and aging , a population - based , prospective study involving a randomly sampled population of 301 men aged > 65 years living in seongnam , south korea . in the latest study , which involved 779 men who lived in yangpyeong county and participated in a prostate examination campaign ,
the wide range of bph prevalence in previous studies  from 11% to 40%is mainly due to methodological differences between studies , such as differences in selection of the target population .
furthermore , the proportion of the population who are elderly is higher in some districts than in others .
the prevalence of clinical bph in south korea is similar to that in western and other eastern countries .
specifically , the bph prevalence in scotland was estimated as 25.3% in 705 men . a cross - sectional study involving 8,466 iranian men ( > 40 years old ) conducted by 74 personal interviewers identified a prevalence of 23.8% when bph was defined as an ipss > 7 , a qmax of < 15 ml / sec , and a pv > 30 ml .
asian data were collected from china , south korea , singapore , pakistan , the philippines , india , thailand , and taiwan .
the prevalences of an ipss 8 points were 18% , 29% , 40% , and 56% among men in their 40s , 50s , 60s , and 70s or older , respectively .
these rates are higher than those reported for the united states ( 12% 17% , 23% , and 29% , respectively )
. this may be due to differences in the cellular composition of prostatic tissue between asians and caucasian - americans .
some studies have reported that asians have more portions that are glandular and less muscle and connective tissue , as well as a transition zone that occupies a higher volume ratio within the prostate .
however , studies use various combinations of parameters to define bph , including symptom score , pv , and urodynamic parameters .
therefore , it remains difficult to determine the exact in prevalence , and to make further progress in the survey method .
even though ui is not life threatening , it is a severe health problem and causes psychological distress , hygiene problems , and social impairment in affected patients and their families . according to the international continence society definition , any involuntary leakage of urine constitutes ui . in general , many women regard ui as a natural consequence of childbirth and aging .
even though ui can be managed in various ways by clinicians , many women tend to manage their ui personally .
in addition , due to shame , many people conceal their problem rather than ask for medical help .
the incidence of ui increases with aging , and with the rapid growth of the aged population , ui is gradually becoming an enormous social burden in south korea .
the earliest prevalence data for ui in south korea were reported in 2004 ; the study comprised an internet survey involving 3,372 respondents , and the prevalence of ui in women was 21% .
an additional large telephone survey reported that the overall prevalence of ui was 40.8% among 1,301 women .
with regard to ui type , 22.9% of cases were stress - type , 3.1% were urgetype , and 14.9% were mixed .
in 2008 , the korean national survey on urinary incontinence yielded nationwide representative data ; in this survey , 13,345 households were interviewed .
the prevalence of ui was 24.4% , and stress ui was the most prevalent type .
a further population - based cross - sectional telephone survey of south koreans included 888 men and 1,112 women .
the most predominant types were other ( 1.3% ) in men and stress ( 20.7% ) in women .
data from 9,873 women participants in the korea national health and nutrition examination survey were reported in 2014 .
this study reported that the overall prevalence of ui among women was 7.9% . by age , the prevalences were 10.1% and 10.3% in women over 40 and 60 years of age , respectively .
the reported prevalences were 0.8% , 4.6% , 9.3% , 10.8% , 10.9% , and 9.7% among women in their 20s , 30s , 40s , 50s , 60s , and 70s or older , respectively .
the  2008 actual living conditions of the elderly and welfare need survey obtained data by personal interview ; this survey attempted to provide longitudinal population information using a cluster sampling method .
the 8,961 women studied , 6.5% had self - reported ui and 2.3% had been medically diagnosed with ui . the most recent population - based , cross - sectional study randomly sampled 500 korean women who reside in the seoul , incheon , and gyeonggi - do areas .
the survey comprised a computer - aided telephone interview , and used 16 questions to collect data ; the questions sought information on demographic characteristics , information sources , disease insights , and general health - seeking behavior . among the responders , 23.8% of women experienced ui .
western data report a prevalence range of 3.9% to 24.4% in women , while asian data have shown variable results : 53.7% of japanese women aged over 40 years , and 27.7% of taiwanese women aged 65 years or older .
korean data on ui have also varied widely ; however , the prevalence is comparable with that of worldwide data , irrespective of region or race . because korea is a conservative country , and koreans are relatively passive in coping with ui problems , ui may be more common among south korean women than is reported
therefore , assessment of the real ui prevalence is the first step to creating public awareness and increasing public knowledge regarding this problem . in this way
oab is a broad terminology that refers to a complex of symptoms such as urinary urgency , urge incontinence with nocturia , and frequent urination .
investigation into the prevalence of oab is still in its infancy , because the definitive characters of oab are obscure in that there is no clear metabolic or histologic explanation for the symptoms . nonetheless , oab is a common voiding dysfunction , especially among older people .
in addition to causing physical problems , oab may have a negative effect on the person s emotions and quality of life ; furthermore , the disorder may eventually place a severe financial burden on society  not only in medical terms , but also through loss of productivity .
the reported incidence of oab has varied significantly among epidemiologic studies , because the diagnostic criteria with regard to each individual urological symptom are different . in south korea ,
epidemiologic studies into oab that had consistent diagnostic criteria began relatively recently , as did studies into the impact of the condition on the individual and society .
we summarized the south korean studies into oab in table 3 . in 2004 , 3,757 participants completed a questionnaire via an internet survey . among the 3,372 women who responded , 429 suffered from oab ( 12.7% ) . in another study
, nationwide community samples were obtained from south koreans aged 40 to 89 years . through a telephone survey that used allocation sampling , choo et al .  
reported that the prevalence rates in men and women were 13.3% and 16.3% for dry - type oab , and 7.5% and 15.0% for wet - type oab , respectively . in 2011 , lee et al .   performed a population - based survey using the international continence society ( ics ) definition of oab
the study was cross - sectional in design and used a telephone survey method to gather data from 2,005 persons .
they found that 12.2% of individuals had oab , with similar rates among men ( 10.0% ) and women ( 14.3% ) . in a regional study in guri city and yangpyeong county , gyeonggi - do , the general oab prevalence was 14.1% ( 12.2% in men and 15.5% of women ) .
the survey involved face - to - face interview of 926 residents , and defined oab when the urgency score was > 2 points and the oab symptom score was > 3 points .
in general , south korean prevalence data range from 10% to 16% , with a higher rate in women than in men .
this is similar to the prevalence found in western countries ; furthermore , the prevalence of oab in south korea increases with age , just as in western countries .
for instance , in a survey involving 5,204 americans , the prevalence of oab was 16.0% in men and 16.9% in women .
data from six european countries revealed that the overall prevalence of oab among 16,776 people was 16.6% . referring again to asia ,
the prevalence among 4,570 japanese respondents was 12.4% , and it was 20.9% among 1,247 taiwanese women .
oab patients are known to have a lower quality of life ; however , investigators require a deeper insight into the condition s harmful influence in the community , especially in south korea .
proper epidemiologic data will be a valuable resource for educating the south korean population about oab  a term unfamiliar to the public at the current time .
according to the 2002 ics definition , the term  luts  encompasses various types of storage , voiding , and postmicturition symptoms . similar to other voiding dysfunctions , luts are a common condition , and their prevalence has positive correlations with age .
one problem with luts prevalence studies is that the condition is difficult to define , and most studies use criteria that overlap with those of bph , ui , or oab . until recently ,
when investigation into luts prevalence began , one innovative study involving south korean men was performed in yeoncheon county .
this community - based epidemiologic study assessed the severity of urinary symptoms in 514 men over 50 years of age .
the overall incidence was 23.2% : 17.7% in those aged 5059 years , 23.3% in those aged 6069 years , and 35.3% in those aged over 70 years . in 2001 , cho et al .  
a total of 1,356 men between 40 and 79 years old living in the seoul area were selected using stepwise random sampling and surveyed with a questionnaire that included questions about ipss .
about 16% had moderate - to - severe luts , defined as an ipss > 7 .
the prevalence of moderate - to - severe luts increased significantly with age , 10% , 16% , 29% , and 45% in the age groups 4049 , 5059 , 6069 , and 7079 years , respectively .
one population - based telephone survey involving 2,000 individuals reported that the overall frequency of luts was 61.4% ( 53.7% in men , 68.9% of women ) .
64.4% of women , voiding luts affected 28.5% of men and 25.9% of women , and postmicturition luts affected 15.9% of men and 13.9% of women .
kim et al .   surveyed a random sample of men older than 40 years .
responses from 1,842 men were investigated , and the overall prevalence of luts was 83.4% .
storage luts ( 70.1% ) were more common than voiding ( 60.4% ) or postmicturition luts ( 38.3% ) .
as can be seen in the above summary , the reported prevalences of luts vary widely , from 16% to 83% .
nonetheless , the south korean prevalence data regarding luts are comparable to those in reports from across the world .
one study in europe found that the prevalences of luts were 16.2%25.1% in men and 12.6%23.7% in women .
moderate - to - severe luts were reported by 36% of men aged 5059 years , 50% of men aged 6069 years , and 60% of men aged 7079 years .
however , there have been fewer epidemiologic studies into luts in asian countries than in western countries , and prevalence data focus mainly on men rather than on the general population ; there are few data regarding the prevalence in women .
as shown in table 4 , the prevalence varies widely between studies worldwide , mainly because investigators still have no clear definition of luts .
the condition is complex , and this is a severe obstacle to researchers who wish to obtain the true epidemiology of luts in south korea .
nocturia is defined by the ics as the  complaint that the individual has to wake at least once at night to void  .
getting up at night to void urine increases the risk of individual physical or mental injuries in elderly people .
nocturia reduces the quality of life and is associated with sleep fragmentation , reductions in productivity , reduced general health , and falls or fractures .
most urologists consider a single episode to be nocturia , but many epidemiologic studies have defined nocturia as more than two episodes of voiding per night .
only a few studies into nocturia have been conducted in south korea ( table 5 ) . in 2008 , choo et al .   conducted a clinically validated , computer - assisted telephone survey . among the 2,005 respondents ( 1,005 women and 1,000 men ) ,
33.5% complained of once - per - night voiding , and 48.2% stated that they had to void twice or more per night .
interestingly , even though the prevalence of nocturia was high , the negative influence on everyday life was reported to be minimal . in 2000
, data were published involving 2,000 participants ( 888 men and 1,112 women ) . according to this cross - sectional telephone survey ,
the prevalences of nocturia ( 2 voids per night ) were 36.6% in men and 48.2% of women . in 2012 , lee et al .   investigated the prevalence of nocturia ( 2 voids per night ) using a face - to - face interview method .
the prevalence was 56.0% in this community - based study involving 439 elderly south korean men in a single city ( seongnam ) .
it is true that not all patients suffer from nocturia , and the degree of impact is influenced by the severity of the condition . to understand the exact epidemiologic nature of nocturia in south korea
, it will be useful to examine to what degree cultural background has an effect on the psychological impact of nocturia .
the prevalence of nocturia in south koreans appears to be higher than that in other communities .
the prevalences of nocturia ( 2 voids per night ) among japanese community - dwelling adults were 28.1% in men and 27.1% in women .
a multistage , cluster sampling study with a personal interview - type design was used to obtain data from 15,988 people in the united states .
the prevalences of nocturia ( 2 voids per night ) were 9% in men and 16% in women .
data collected from 1,247 women and 1,221 men in austria showed that 37.2% of men and 43.1% of women experienced 1 voids per night , and that 7.5% of men and 8.1% of women experienced 2 voids per night .
these lower prevalences in other populations may have been affected by the population distributions studied , as well as by the definition of nocturia used .
nonetheless , the probable causes of the high prevalence of nocturia among south koreans remain to be clarified .
epidemiologic surveys are essential for understanding the potential causes and characteristics of related medical disorders . in addition , they are the necessary first steps in evaluating psychosocial impacts of a disorder . in general ,
most of the estimated prevalences of voiding dysfunctions in south korea were similar to those in other countries ; they varied widely , primarily due to different definitions of the respective disorder .
in addition to the lack of solid definitions of voiding dysfunctions , inconsistencies in integrated questionnaires and variances among target populations render population - based surveys difficult to compare .
most investigations were based on self - reported symptoms , so recall bias and person - to - person social bias may have been present , especially in personal interviews .
nonresponse bias could also be a problem in that nonresponders to a survey may have been significantly different from responders in terms of the respective symptoms .
population - based surveys are carried out because diagnosis by strict medical assessment is not practical in such large - scale prevalence studies .
nonetheless , researchers need to develop other ways to obtain more proper , valuable epidemiologic data .
we think that investigators should focus on unifying all of these disease entities and definitions .
more efficient investigational processes and methodologies are also warranted . from a methodological point of view , 14 of the studies ( 58.3% ) included in the present report , involved personal interview data . despite considering the advantages of the personal interview ,
however , the bashful and conservative nature of koreans may prevent investigating the epidemiology of voiding dysfunction in simpler , less time - consuming ways . as a result ,
relatedly , the random digital dialing in telephone surveys is often perceived as violating personal privacy ; for this reason , telephone surveys will not be easy to conduct in the future .
due to the noteworthy progress in multimedia technology in south korea , epidemiologic studies using the internet and other applications are a promising method . using web services
an internet survey can gather enormous amounts of data from large groups within a relatively short time .
furthermore , videos or pictures can be used easily , at reasonable cost , and with less social desirability bias than the other study methods .
mobile communication techniques may improve methothologic efficiency in various social and natural science fields , as well as in medicine .
for example , bladder diary apps may exclude the disadvantages of pen - and - paper diaries in clinical application . currently , the apps available vary in quality , but there is room for medical associations to collaborate with developers in this area . even though some of the public are not familiar with surveys by internet or electrical devices , much progress will be made in epidemiologic studies due to technology , especially with regard to methodology .
this review constituted a nationwide representative summary of studies on the prevalence of voiding dysfunctions in south korea .
we hoped to contribute to the understanding of voiding dysfunctions by providing the epidemiologic characteristics of each condition .
however , much work remains to be done in this field , because few surveys had a longitudinal design , and more investigations are needed that consider the whole range of age , sex , and location in the south korean population .
given the influence of voiding dysfunction on quality of life , as well as the socioeconomic burden of the condition , more studies on the optimal approaches to epidemiologic study will be needed in the future .
 this review assessed the epidemiology of voiding dysfunctions in south korea . 
 comprehensive understanding of this epidemiology is crucial because the senior population and the social burden are increasing because of voiding dysfunctions is growing . 
 we searched the medical records using several terms related to voiding dysfunction : benign prostatic hyperplasia , urinary incontinence , lower urinary tract symptoms , overactive bladder , and nocturia . 
 we then estimated the prevalence of voiding dysfunctions in south korea ; our data were comparable with those from other countries , with slight differences . 
 the ranges of incidences varied widely between studies , mostly because investigators defined disorders differently . voiding dysfunction 
 greatly affects healthcare costs and individual quality of life ; therefore , more proper and valuable epidemiologic data are needed . 
 in addition , efforts to unify the definitions of various voiding dysfunctions and progress in investigational methodologies using multimedia are warranted . 