Lichen planopilaris and frontal fibrosing alopecia are primary scarring alopecias where diagnosis can be suggested by clinical and trichoscopy features, especially in the early stages, but scalp biopsy is the standard exam for definitive diagnosis. Frontal fibrosing alopecia is considered a variant of lichen planopilaris, as the histopathological findings are similar, with a perifollicular lymphohistiocytic infiltrate, sometimes with a lichenoid pattern. A thorough clinical examination, trichoscopy and photographic documentation are essential to assess the evolution and therapeutic response. To date, there are no validated treatments or guidelines for these diseases, but there are recommendations that vary with the individual characteristics of each patient. This article presents a comprehensive review of the literature, including an update on topics related to the diagnosis, follow-up, histopathological aspects and available treatments for lichen planopilaris and frontal fibrosing alopecia, highlighting their similarities, differences and peculiarities. Frontal fibrosing alopecia (FFA) is a primary lymphocytic scarring alopecia, considered a variant of lichen planopilaris (LPP) due to its histopathological. Clinically, FFA causes hair loss that occurs slowly in the frontotemporal implantation hairline, commonly associated with eyebrow alopecia. In addition to the scalp, other manifestations may arise, such as lichen planus pigmentosus, facial papules, body hair involvement, hypochromic lesions, diffuse erythema on the facial and cervical regions, evident frontal veins. On the other hand, classic lichen planopilaris (LPP) shows an area of irregular alopecia that is more common in the vertex region, single or multifocal, and may occur in other places on the scalp, but without a characteristic band distribution . Graham The present article aims to review the diagnostic aspects, inflammatory activity, follow-up, and treatments of the two diseases, highlighting their similarities, differences and peculiarities.The presence of clinical and trichoscopic findings characteristic of LPP or FFA could replace scalp biopsy in the opinion of some authors.A list of diagnostic criteria for FFA was proposed by Vañó-Galván et al. in a 2018 publication.There are no specific laboratory tests for LPP or FFA. Previous studies have demonstrated the occurrence of LPP in chronic inflammatory and autoimmune diseases, as well as a significant prevalence of autoimmune diseases and thyroid abnormalities in FFA patients when compared to the normal population.Some disease activity and severity classifications have been proposed for these diseases in recent years.In 2010, an LPP activity index (LPPAI) was introduced by Chiang et al. for a more objective approach to the clinical course and therapeutic response.In 2016, Holmes et al. proposed the FFA severity index (FFASI) as an assessment method for clinical practice and scientific publications . The FFASome authors criticize the FFASI scoring system for considering it complex for clinical practice, with criteria that do not properly represent the FFA prognosis and that lack validation. As a result, in 2018, a new FFA severity score (FFASS) was proposed that included clinical features, such as the extent of frontotemporal alopecia, loss of eyebrows, peripilar erythema, peripilar desquamation, pruritus, and pain . The sevIn our clinical practice, it has been observed that many patients being followed for LPP and FFA, without inflammatory symptoms or signs, continue with progression of the area of alopecia. On the other hand, a study with 62 women with FFA showed that one in four patients undergoing treatment, even with disease stability, had persistent symptoms and inflammatory signs. Moreover, some patients had worsening and progression of alopecia without inflammatory signs, suggesting that inflammatory infiltrates restricted to the isthmus are not visible on the skin surface.The degree of FFA progression is difficult to predict, but some studies mention factors related to prognosis. A clinical pattern of diffuse involvement of the frontotemporal recess, loss of eyelashes, loss of body hair, and presence of facial papules were indicators of a poor prognosis.11A scalp biopsy allows the diagnostic confirmation of scarring alopecia. It must be performed with a 4-mm punch biopsy, with one sample submitted for vertical sections and the other for cross-sectional sections. The cross-sectional or horizontal sections ensure the observation of all follicles in the sample at different depth levels. The vertical or longitudinal sections are appropriate for the evaluation of alopecias with pathological alterations in the epidermis and dermo-epidermal interface .The histopathological alterations found in LPP are: a perifollicular lymphohistiocytic infiltrate, sometimes with a lichenoid pattern, more prominent in the upper portion (isthmus and infundibulum regions); vacuolar degeneration of basal cells, necrotic keratinocytes, and artifactual clefts between the follicle and the perifollicular fibrous band; perifollicular fibrosis can be seen separating the inflammatory infiltrate from the follicle . Over tiDirect immunofluorescence (DIF) is used to detect antibody deposits in lesional and perilesional tissue. It has shown to be useful in the differential diagnosis of some scarring alopecias such as LPP and lupus erythematosus. When DIF is positive in LPP, it shows a pattern of globular deposits, cytoid bodies  clustered adjacent to the follicular epithelium, irregular fibrinogen deposition, and C3 deposits in the papillary dermis. A linear band of immunoreactivity  is typical of lupus erythematosus (LE).FFA is considered a variant of LPP because it shows indistinguishable histopathological findings . In the Poblet et al. (2006) described eight cases of each disease, also using DIF in two cases of FFA and in four cases of LPP. They found more prominent inflammatory infiltrate and fewer apoptotic cells in LPP than in FFA, but it was not enough to consider these diseases distinct concerning their histopathology. Regarding DIF, the result was negative for FFA and positive for two cases of LPP.Cerqueira et al. (2016) compared ten cases of LPP and FFA, also using DIF and immunohistochemical markers . No significant differences were observed between the diseases.Donati et al. (2017) evaluated the DIF results in patients with FFA and found 29.5% of positive results, with 9% showing a pattern similar to LPP, 7% an LE pattern, and 13.5% non-specific patterns. The study concluded that the DIF of FFA does not have the same diagnostic value as in LPP and LE, being, in most cases, negative and without a specific pattern.versus 63%; p = 0.02) but found no differences between the inflammatory infiltrate intensity in the two diseases.Wong and Goldberg (2017) compared 32 cases of LPP and 37 cases of FFA. They found statistically significant differences between the extent of the inflammatory infiltrate below the isthmus in FFA when compared with LPP ; intense perifollicular peripheral inflammatory infiltrate  and concentric lamellar fibroplasia zone .Gálvez-Canseco et al. (2018) analyzed 20 histopathological parameters in 34 patients with LPP and 44 with FFA; however, they only observed three statistically significant histopathological parameters. The presence of terminal catagen telogen hairs  performed a study to analyze histopathological, immunohistochemical , and hormone receptor profile (ER-b estrogen beta and androgen receptor) findings in affected and unaffected areas of the scalp of patients with FFA. Perifollicular inflammatory infiltrate was observed in both areas, but with greater intensity in the affected site. FOXP3+ regulatory T (Treg) cells were paradoxically increased in the affected areas when compared to the healthy scalp. There were no differences in relation to the hormone receptor profile.However, a subsequent study with immunohistochemical analysis indicated a significant difference between LPP and FFA, with a higher number of CD68+ cells in the LPP samples. There was also a decrease in CD86 expression and an increase in CD163 and IL-4 expression in lesional LPP when compared to FFA samples. The data suggested that macrophages exist in different functional phenotypes in the two diseases , with emphasis on CD86 and CD163 as potential markers to differentiate between the conditions.To date, although some histopathological features have been shown to be different between FFA and LPP, the differences are considered subtle or non-specific to reliably differentiate them. Therefore, as in previous studies, clinical correlation is essential for the differential diagnosis between the diseases.The goal of treating LPP and FFA is to prevent progression of the scarring alopecia area and to improve symptoms. The therapeutic choice will depend on several factors such as: age of the patient, location of the clinical lesion, stage of the disease, presence of symptoms, comorbidities, and histopathological inflammation.The management of these diseases is challenging. The level of evidence for current therapies is weak, with case reports, case series, expert opinions, and a few controlled studies. There are some recommendations, but to date, there are no specific treatment guidelines for LPP and FFA.Intralesional and topical corticosteroids are considered the first-line treatments for LPP.High potency topical corticosteroids can be used together with intralesional therapy for a faster clinical response. Clobetasol propionate lotion or cream, up to twice a day, is a therapeutic alternative. Lyakhovitsky et al. reported a low success rate in patients treated with topical corticosteroids (eight responders of 42 patients on monotherapy), whereas they observed better results with intralesional corticosteroids (11 responders of 15 patients on monotherapy).Oral corticosteroids are reserved for more extensive manifestations, very symptomatic patients and those with rapid progression. Prednisone at a dose of 1 mg/kg/day can be administered with dose adjustment after one month. There is also the alternative of temporary use, due to the rapid mechanism of action, acting as a bridge to the effect of longer-lasting drugs such as methotrexate.Hydroxychloroquine is used in the treatment of LPP, especially in more extensive cases. Although its exact mechanism of action on the disease is uncertain, it is believed to be related to antigen presentation, cytokine production, and stimulation of toll-like receptors 9.versus methotrexate (15 mg weekly) administered for six months in refractory cases of LPP.There is a randomized clinical trial evaluating the use of hydroxychloroquine (400 mg daily) Other studies have reported success rates with the use of hydroxychloroquine, ranging from 40.1% to 76%.Immunomodulators are therapeutic alternatives in patients with the difficult-to-control disease. Some options pointed out in the literature are cyclosporine, 3-5 mg/kg/day; mycophenolate mofetil, 500 mg twice daily; and oral methotrexate, 15 mg/week.28Several different treatment modalities are reported for refractory LPP, with inconsistent results. Some of them are systemic retinoids, tetracyclines, thalidomide, dapsone, pioglitazone, topical calcineurin inhibitors, griseofulvin.30Isotretinoin and oral acitretin have shown beneficial effects on generalized and erosive lichen planus, which led some authors to expand their use to LPP. However, discreet results and high recurrence rates were observed after discontinuation. Common side effects are xerosis, cheilitis, conjunctivitis.25Studies on the use of tetracyclines for LPP are disappointing. Spencer et al. reported that only 27% of patients treated with oral doxycycline (200 mg/day for three to six months as monotherapy) had positive responses.24Topical calcineurin inhibitors have demonstrated a beneficial effect in inducing the anagen phase in animal models.In recent years, Janus kinase (JAK) inhibitors have been studied especially in the treatment of alopecia areata, as they are small molecules involved in inflammatory signaling pathways, reducing inflammation. The effect of tofacitinib, a pan-Janus kinase inhibitor , was retrospectively evaluated by Yang et al. in 10 patients with recalcitrant LPP (8 classic LPP and 2 FFA). The dose used was 5 mg orally, two to three times a day for two to nineteen months as monotherapy or adjuvant therapy. Eight of ten patients showed improvement (4 as monotherapy and 4 as adjunctive therapy). The reduction in the LPPAI activity index ranged from 30 to 94%. As an adverse effect, only one patient complained of weight gain.Another recently studied drug was oral minoxidil. A retrospective study evaluated the impact of its use in 51 patients with classic LPP, with a dose ranging from 0.25 to 1 mg/day. There was an increase in hair thickness in the unaffected areas adjacent to the alopecia, leading to better coverage.The challenge in the treatment of LPP was evidenced in a retrospective study, demonstrating that 42.9% of a total of 261 patients with classic LPP required drugs from three different classes, and 11.3% did not achieve a complete response. All patients received topical corticosteroids as monotherapy or combined with systemic agents. Among the relatively effective drugs with total or partial response were: cyclosporine 100% ; methotrexate 85% (in 26 patients); mycophenolate mofetil 76% (in 66 patients); prednisolone 68% (in 22 patients); intralesional corticosteroid 43% (in 7 patients); and hydroxychloroquine 59% (in 68 patients). The median time to achieve complete and partial remission was 6.1 ± 6.5 and 2.7 ± 3.9 months, respectively.FFA is a chronic disease with a variable course and possible spontaneous stabilization, which often makes it difficult to assess the effectiveness of treatment modalities.Topical therapy recommendations in the literature include high-potency corticosteroids, intralesional corticosteroids, and calcineurin inhibitors. The main systemic treatments are 5 alpha-reductase inhibitors, hydroxychloroquine, and retinoids. Some studies report the use of tetracyclines, methotrexate, pioglitazone, naltrexone, and JAK inhibitors (tofacitinib).Intralesional corticosteroid use (triamcinolone acetonide) is one of the most commonly used therapeutic options in FFA, especially for lesions in well-delimited areas, implantation hairline, and eyebrows.Topical high-potency corticosteroids and topical calcineurin inhibitors have shown beneficial effects in improving symptoms but little effect in controlling disease progression.in vitro study demonstrated that minoxidil significantly reduced the total amount of collagen (30% inhibition) in cultured rat dermal papilla cells, with a possible antifibrotic effect.Topical minoxidil 5% can be used to improve hair coverage on the scalp, especially in patients with associated androgenetic alopecia. Additionally, an FFA is currently understood as a generalized disease that affects all body hair and is associated with several skin alterations, such as papules on the face and lichen planus pigmentosus. Therefore, systemic therapies are often necessary.The 5-alpha-reductase inhibitors (finasteride and dutasteride) are systemic drugs that have shown positive results in the treatment of FFA, even in patients without associated androgenetic alopecia.There is a case report showing improvement in inflammatory signs, cutaneous atrophy, and repilation in the frontotemporal region of a patient with FFA after the introduction of finasteride 2.5 mg/day.A review study on the efficacy and safety of 5 alpha-reductase inhibitors for FFA reported only two publications with a moderate level of evidence; lack of dose standardization ; combined use with other therapeutic agents; positive results in recalcitrant disease. The use of 5 alpha-reductase inhibitors was considered positive due to the good results, with a reduction in disease progression. There is limited evidence on the safety profile. The use in women of childbearing age should be cautious due to teratogenicity. Although some authors have reported a protective effect in breast cancer,A recent retrospective observational study on the use of oral dutasteride in FFA in 224 patients with a mean follow-up of two years showed that the medication was the most effective therapy compared to other systemic therapies or no systemic treatment. The stabilization rate for the frontal, right, and left temporal regions after 12 months was 62%, 64%, and 62% in the dutasteride group (n = 148), 60%, 35%, and 35% with other systemic therapies (n = 20) and 30%, 41% and 38% without systemic treatment . The stabilization showed a statistically significant association with an increasing dose of oral dutasteride with a weekly treatment of 5 to 7 doses of 0.5 mg. The medication was well tolerated in all patients.The main targeted therapies against the lymphocytic inflammation of FFA are hydroxychloroquine and doxycycline. These drugs have anti-inflammatory properties and an acceptable adverse effect profile.versus 50% with no response after one year.Studies using doxycycline 100 to 200 mg/day have shown inconsistent results. A retrospective study reported 50% improvement in signs and symptoms of FFA versus 43% in the finasteride group. And the response was maintained one year after drug discontinuation .Systemic retinoids are also thought to have an anti-inflammatory effect on FFA and may lead to normalization of the antigenic expression of follicular keratinocytes, but the exact mechanism of action remains unknown. The retrospective cohort study by Rakowska et al. evaluated groups treated with oral isotretinoin 20 mg/day and oral acitretin 20 mg/day and compared them with the group treated with oral finasteride 5 mg/day. Disease stabilization was observed in 79% in the isotretinoin group, 73% in the acitretin group Retinoids have also shown beneficial effects in the treatment of facial papules and lichen planus pigmentosus in studies using oral isotretinoin 20 mg/day.PPAR-gamma agonists (pioglitazone) have been used in FFA, but with variable results and many adverse effects. A retrospective cohort study reported disease stabilization in three of four patients, but the evaluation was carried out for a short period, one to three months, and in a small sample. The main adverse effects were edema of the extremities, weight gain, and dizziness.Naltrexone is an opioid antagonist with anti-inflammatory properties and an alternative treatment, at low doses, for scarring alopecia. It seems to be able to reduce symptoms, inflammatory signs, and disease progression.Immunosuppressive agents can be used in refractory cases of FFA, but there are scarce data in the literature and inconsistent results.Gerkowicz et al. evaluated the effectiveness of diode laser (LED) devices as an adjuvant treatment in scarring alopecia.Hair transplant surgery has been considered an optional approach for cases with a high impact on the patients quality of life. Some points that should be considered are: clinical stabilization does not necessarily imply disease remission; reactivation can lead to graft loss; the surgical procedure may be responsible for the reactivation of the disease (Koebner phenomenon).A retrospective multicenter study evaluated 51 patients with FFA submitted to hair transplant surgery, performed after a mean of 15 months of stabilization . The follicular unit extraction technique was performed in 14% of the cases and the band technique in 86% of the cases. The most frequent locations were: temporal region (59%), frontal region (44%), and eyebrows (29%). All patients maintained the drug treatment for FFA after transplantation. The mean graft survival after 1, 2, 3, and 5 years of follow-up was 87%, 71%, 60%, and 41%, with a significant decrease after five years. However, the patient satisfaction rate was 82%.FFA is considered a variant of LPP due to the histopathological similarities, but with several peculiarities ranging from clinical aspects to variations in therapeutic response. The scientific literature suggests that, to date, there are no histological or immunological findings that allow us to accurately differentiate these two forms of primary scarring alopecia.The best method for evaluating the inflammatory process, which allows proving undeniable evidence of fibrosis, is the histopathological examination. Moreover, inflammation at the isthmus level is not fully translated by the clinical signs and symptoms described for these diseases, which can impact the therapeutic decision.The absence of randomized clinical trials does not allow drawing definitive conclusions about the most effective of the available treatments. Furthermore, most studies evaluate patients with combined treatments, so the best choice will be made on a case-by-case basis. The therapeutic approach to LPP and FFA may also vary with patient evolution and follow-up. Therefore, photographic documentation and trichoscopy are essential to assess disease progression or stabilization.None declared.Carolina Oliveira Costa Fechine: Approval of the final version of the manuscript; design and planning of the study; drafting and editing of the manuscript; collection, analysis, and interpretation of data; intellectual participation in the propaedeutic and/or therapeutic conduct of the studied cases; critical review of the literature; critical review of the manuscript.Neusa Yurico Sakai Valente: Approval of the final version of the manuscript; effective participation in research orientation; intellectual participation in the propaedeutic and/or therapeutic conduct of the studied cases; critical review of the manuscript.Ricardo Romiti: Approval of the final version of the manuscript; effective participation in research orientation; intellectual participation in the propaedeutic and/or therapeutic conduct of the studied cases; critical review of the manuscript.None declared.


Background: To determine whether population-adjusted rates of physical rehabilitation need  are associated with the workforce supply  and occupational therapists (OTs) per 10 000 population) across high-income countries (HICs), adjusted for socio-demographic and economic covariates.Methods: This is a cross-national ecological study. Hierarchical, multiple linear regressions analyzed current international data across 35 HICs using: current PTs and OTs supply data obtained from the international professional federations (outcome variable); needs data obtained from the Global Burden of Disease 2017 (GBD 2017); and finally relevant socio-demographic variables and supply-side covariates extracted from the World Bank, GBD 2017, the supply data sources, and the Global Health Expenditure Database.Results: The PTs and OTs per capita varied greatly across the 35 HICs, differing by as much as 40-fold. Denmark had the greatest supply per capita. Physical rehabilitation need was not a significant, independent predictor of workforce supply regardless of the multiple regression model used (P >.10). In the final model, after Bonferroni correction, 3 covariates were significant, independent predictors of the supply variable: gross national income (GNI) per capita and the current health expenditure in % of gross domestic product (GDP) were positive factors for workforce supply, while population size was a negative factor .Conclusion: PT and OT workforce supply is highly variable across HICs. This variability is not accounted for by an indicator of population need but rather by financial indicators and population size. Implications for policy makersPhysical therapist (PT) and occupational therapist (OT) workforce supply is highly variable across high-income countries (HICs), and that was not accounted for by a composite indicator of population need, in contrast with financial and population size factors. These findings suggest substantial supply-need disparities across HICs. Deliberate, data-based physical rehabilitation workforce policies and planning should be developed as a result. Population size and, marginally, the percentage of rural population were two factors associated to the PT and OT workforce supply. People living in rural areas in countries with a larger population, may be facing a double disparity, or double ecological risk, of facing needs-based shortages of PTs and OTs, if explicit policies are not in place. Ecological findings need to be complemented with country-specific data and analyses, as not all countries  fitted the ecological trend identified. Countries with trends identified as at the odds with the ecological trend may be at a more pressing need for implementing deliberate workforce policies. Implications for the public Large physical therapist (PT) and occupational therapist (OT) workforce supply disparities were found across the 35 high-income countries (HICs), for relatively equivalent levels of population need. While population need was not significantly, independently associated with the PT and OT supply, population size and two financial factors were: gross national income (GNI) per capita, and the current health expenditure in % of gross domestic product (GDP). Altogether, while demand-side factors were associated to PT and OT supply, needs-based were not. Items on government spending in healthcare were not significant factors in this study. Yet, the five Nordic countries were within the top six in the PT and OT supply. The use of composite indicator of physical rehabilitation need, derived from the Global Burden of Disease 2017 (GBD 2017) and available since 2019, can be used in rehabilitation workforce supply and requirements studies, in addition or in complement to demand-based factors. Uncovering supply-need disparities across HICs may help drive further, deliberate policies to close them.5 This study aims to test whether current physical rehabilitation need is independently associated with current rehabilitation workforce supply in high-income countries (HICs). The determination of the health and rehabilitation workforce supply  should account for the population need  for these services.10 Global population ageing and higher rates of chronic conditions, disabilities and physical rehabilitation needs are growing in tandem.13 Since 1990, there has been a significant growth of physical rehabilitation needs per capita worldwide, including a 16% growth in HICs (P <.01).14 However, the rehabilitation workforce remains an understudied and often neglected health workforce.15 Furthermore, imbalances in the rehabilitation workforce supply are present among countries, even in HICs, with large variations observed.17 For example, in 2014, Singapore had a number of physical therapists (PTs) per capita 4.3 times lower than Portugal’s, even though the gross domestic product (GDP) was over than 3 times higher.16 Deliberate needs-based workforce policies, including planning and research, are needed to ensure the equitable accessibility of health workers to the population.20 It is poorly known whether the physical rehabilitation ‘needs’ of the population are a key determinant of its supply. Gupta et al15 used descriptive statistics and simple regression models to compare supply of and need for the rehabilitation workforce. However, this seminal research is based on data from low-income countries to HICs up to 2008. Their study did not adjust the findings for relevant socio-economic and health expenditures data, and it used years of life lost to assess rehabilitation needs – a metric of the Global Burden of Disease (GBD) study that emphasizes premature mortality outcomes. More recent, disability-focused and reliable data for determining rehabilitation needs and supply are currently available,14 and can be used alongside other relevant health and socio-economic indicators to understand the determinants of the rehabilitation workforce supply. The ‘right’ size of the health and rehabilitation workforce must not be determined solely by ratios of providers per population, but must account for other variables, including population needs.3 In HICs, the developments of rehabilitation services and workforce are not in its infancy, thereby an alignment among the rehabilitation workforce supply and need is much more likely and expected – and can be tested against that hypothesis. This contrasts with the many low- and middle-income countries (LMICs), where rehabilitation needs are known to be largely unmet15; for instance, the World Health Organization (WHO) estimated that qualified rehabilitation professionals are about one-tenth of those required in many LMICs.11 Nonetheless, whether unmet rehabilitation needs or needs-based inequalities in workforce supply exist among HICs is still unclear. This study focusses on HICs, where rehabilitation workforce data are more available and more robust and reliable, hence with greater comparability across nations. Hence, with a focus on HICs, this paper aims to test the hypothesis that physical rehabilitation need, based on disability-focused data. ie, years lived with disability (YLDs) from the GBD 2017 is independently associated with physical rehabilitation workforce supply  10 000 population), ie, after adjusting for socio-economic and demographic variables. This is a cross-national, ecological study, using global health, workforce, and socio-demographic data available in the public domain.dependent  variable is the physical rehabilitation workforce supply, which here is the population-adjusted combined number of practicing PTs and OTs, provided by the international professional federations.22 To compute this variable, we summed up the number of practicing PTs and OTs per 10 000 population for each HIC, according to the World Bank’s Classification of 2019. Data on the numbers of practicing PTs and OTs were retrieved from databases of the World Confederation for Physical Therapy (now known as World Physiotherapy), and the World Federation of Occupational Therapists.22 Both federations have active human resources projects mapping these professionals across countries, using best-available data, collected by the national professional associations, under a standard international procedure.22 Hence, we had reliable, internationally comparable supply data for these two rehabilitation professions whose scope of practice partly overlap.16 We consulted the WHO’s Global Health Workforce Statistics database (https://www.who.int/hrh/statistics/hwfstats7en/) and observed that the existing data for rehabilitation professions were less up to date, from variable sources and timings, and less comparable across countries. The supply data, extracted in July 2019, is current to November 2, 2017 for practicing OTs,22 and to June 30, 2018 for practicing PTs.21 We used the country population estimates from the GBD 2017 as the denominator for the ratio.23 The independent variable is the total amount, as of 2017, of physical rehabilitation ‘needs,’ adjusted for population size. To compute this variable, YLD rates per 10 000 population were extracted from the GBD 2017 for each rehabilitation-sensitive health condition, and then summed up to provide a composite indicator of physical rehabilitation need per country.24 YLDs is the aggregate measure of the GBD study that focusses exclusively on non-fatal health losses; it is computed using the prevalence of health conditions, the time people typically live with sequalae from those conditions, and a disability weight for the severity level.24 All these factors are relevant for determining physical rehabilitation needs, especially when combined into one measure. For instance, spinal cord injuries are not as prevalent as ankle sprains, but more often leave long-term sequalae, can be severe, require intensive physical rehabilitation, and for longer periods of time. In this example, relative to prevalence, YLDs are less prone to overestimate the need for physical rehabilitation from ankle sprains as well as less prone to underestimate physical rehabilitation needs arising from spinal cord injuries. Overall, YLDs is a more balanced measure of rehabilitation need across health conditions when compared to prevalence. The main 14 To determine which YLDs in the rate metric were relevant to physical rehabilitation, we used the set of conditions which were determined as responsive to physical rehabilitation interventions. Causes Communicable, Maternal, Neonatal or Nutritional:HIV/AIDs Leprosy; Zika Meningitis, Encephalitis; Tetanus Neonatal disorders  Non-communicableNeoplasms Cardiovascular diseases (includes stroke) Chronic respiratory diseases Neurological disorders, except epilepsy and migraine (tension-type headaches included) Autism spectrum disorder Musculoskeletal conditions (includes low back pain and neck pain) Congenital birth defects, except urogenital and digestive  Injuries (nature of the)Amputations Burns Fractures, except skull Head injuries Spinal injuries Minor injuries: muscle and tendon injuries; including sprains and strains lesser dislocations; Open wound(s) Dislocation of hip; Dislocation of knee; and Dislocation of shoulder Asphyxiation Crush injury; Nerve injury; Severe chest injury Multiple fractures; dislocations; crashes; wounds; pains; and strains  Impairments (from the non-selected “causes” combined)Heart failure Guillain-Barré syndrome  Abbreviations: GBD, Global Burden of Disease; YLD, year lived with disability.covariates for which we collected data on countries’ socio-economic and demographic variables that could affect, theoretically, the ‘demand’ for rehabilitation services above and beyond need.22 This metric is computed using data on fertility, education and lag distributed outcome per capita, and strongly correlated with health outcomes. Note: The supply-side covariates are extracted from the same sources of the supply data – the outcome variable. We collected the last available data for a total of 37 HICs with supply data for PTs and OTs. Portugal and Estonia only had PT supply data up to 2015, and Switzerland up to 2017; all others had data up to 2018. We ran pilot analyses with and without Portugal and Estonia, and then with or without these and Switzerland as well. As the statistical significance of the main results  was no different, we excluded the data from Portugal and Estonia but kept that of Switzerland – as the date was similar to other included countries . Hence, we included current supply data for 35 countries, including Switzerland, into our final analysis. yes or no, were transformed into ‘dummy’ variables of values 1 and 0, respectively. We conducted a simple linear regression for the unadjusted effect of the main independent variable (need indicator) on the outcome variable (PTs and OTs rates). Then, we built a multiple linear regression with all covariates included. Categorical covariates, whose qualitative value were P values >.05) or that had tolerance values <0.2. As a result, we retained only 3 covariates . Then, we progressively reintroduced into the shortened model, one by one, all the eliminated covariates . If reintroducing one variable significantly improved the model fit , that covariate was retained. The process was repeated for all the covariates until we could no longer significantly improve the fit of model in progress. This whole process yielded 2 additional covariates  for the final model. Compared with the initial model, there were no significant differences in explained variance . Hence, we only present the final model in the main results. The initial model is available on demand. Subsequently, to build a model containing only the covariates that were found relevant for the data, we started by eliminating all the covariates that had no significant relationship with the outcome variable (Q-Q plot. The Durbin Watson test did not support the presence of autocorrelation (P = .96). No item had low tolerance , and overall the model had a relatively good fit . Statistical significance was considered at P values < .05 for the main independent variable. Yet, for the 5 other covariates, 2 levels of statistical significance were applied: one with P values < .05 and another with P values of < .01; the latter accounts for a Bonferroni correction (0.05/5 = 0.01). The full statistical analysis was run using JASP 0.10.20 software. For final model, homoscedasticity and normality assumptions were positively assessed respectively by plots of standardized residuals versus predicted values and a  The supply of PTs and OTs per 10 000 population (mean = 15.7) varied widely across 35 high-incomes countries (SD = 10), ranging from 0.9 to 38.7, respectively for Trinidad and Tobago and Denmark . With respect to need for physical rehabilitation, the YLD Rates  ranged from 3345 in Panama to 8411 in Slovenia .P = .03), the relationship did not have a good fit in the linear regression (r2 = 0.13), and only slightly fitted better in a logarithmic type of regression (r2 = 0.31).P = .11) . Adjusting for the relevant covariates, the physical rehabilitation need was not a significant, independent predictor of the workforce supply (P = .11) , which aP = .03), while the percentage of rural population was marginally negatively related (P = .053) (P <.01). The existence of PT assistants was a significant negative factor for the supply, at a 95% confidence level only ( = .053) . GNI per30 our findings suggest that demographic and economic indicators are more significant determinants of PT and OT workforce supply in HICs than a composite indicator of physical rehabilitation need. The data did not support the hypothesis that physical rehabilitation need was independently associated to the workforce supply in HICs. However, after Bonferroni correction, other factors were associated to supply. Indeed, PT and OT supply was positively predicted by a lower population size, higher GNI per capita, or higher healthcare expenditure as percentage of GDP. Even though ‘needs-based’ workforce policies and planning have been increasingly advocated,3 The few studies that map the rehabilitation workforce distribution within a country31 or forecast national workforce shortages/surplus,26 against supply requirements, have relied on ‘demand-based’  rather than ‘needs-based’ indicators.33 Arguably, demand-side factors reflect pressing labor-market and economic forces,31 some of which this study have found relevant. Another explanation is that the composite indicator of physical rehabilitation need, derived from the GBD 2017, only became available in 2019.14 Previously, other indicators of need used in rehabilitation workforce studies have been based merely on demographic trends30 or on data from community health surveys.34 Finally, local and global stakeholders’ awareness has emerged only recently for the need to monitor, plan and develop rehabilitation resources, in tandem with the growing awareness of population ageing and the increasing rates of chronic conditions, disabilities, and corresponding physical rehabilitation needs.38 Various factors may explain these findings. For instance, health workforce policies, planning, monitoring, and research activities were found rarely documented in the physical rehabilitation field.40 For instance, the social, school-based , and broad welfare services in Nordic countries may create a high demand for therapists, beyond what the health sector  could account for in the model.42 Whatever the reasons, the supply data convey that different countries/societies have substantially different numbers of population-adjusted PTs and OTs, for relatively equivalent levels of population need. This suggests substantial supply-need disparities across HICs. Within the 35 HICs, great disparities were found for the OTs and PTs supply per capita, eg, up to 40 times the difference. Our inferential analysis showed that such a disparity was not explained by varying need levels; the latter had a more sensible variation, eg, up to 2.5 times the difference. We also found that the five Nordic countries are among the top six countries with the greatest OTs and PTs supply. Given that the level of government spending on healthcare proved not to be a significant covariate in this study, we speculate that the Nordic egalitarian culture, ethos and social policies, especially toward fulfilling the needs of the disadvantaged , may have had an important role.P = .053). Together, these findings suggest that less densely populated areas, of countries with a vast population, may have a higher risk of not having enough PTs and OTs available. Such ecological trend is aligned with the Human Resource for Health literature in general,44 and that of the physical rehabilitation field in particular.46 For example, a study in the Province of Saskatchewan in Canada, using both need and PT supply indicators, found that the population that lived in rural areas were especially undersupplied compared to urban areas.34 Altogether, people living in rural areas in countries with a larger population, may be facing a double disparity, or double ecological risk, of facing needs-based shortages of PTs and OTs. Although not directly analyzed, within-country disparities may have been latent factors. We found that having a larger population negatively influenced the supply of PTs and OTs per capita, while having a higher percentage of rural population was marginally related  GNIs per capita of the group, a population size about six times smaller than the average of the 35 HICs, and no rural population. Each of these the indicators, in the ecological trend, were associated to a higher PT and OT supply. But Singapore is amongst the least supplied, ie, fourth to last. This can be explained by the fact that Singapore only recently started PT and OT degree programs in a local university in 2016 and an accelerated professional conversion program in PT for mid-career locals in 2019.51 This finding hints to the need for complementing broad and large-scale ecological analysis with country-specific or nuanced, contextualized, and qualitative analyses of workforce data across fewer geographies16; it also highlights that countries with trends identified as at the odds with the ecological trend may be at a more pressing need for implementing deliberate workforce policies, which for example Singapore is recently doing so, ie, devising and implementing policy-driven expansion plans for the PTs and OTs workforce.52 Apart from the aggregated ecological trend across HICs, attention needs to be paid to individual countries and contexts. For instance, Singapore is representative of the “ecological fallacy” in our study, ie, inference based on aggregate data for the whole group does not necessarily apply to individual entities within the group.28 That can be an issue in the physical rehabilitation field, in which the practices and competencies of each type of rehabilitation professional can vary widely across countries, even HICs; and, for example, PT assistants in some countries perform roles that PTs typically perform in others where assistants do not exist officially.20 Although actual rehabilitation practices and competencies would be optimal in such a context, a practices- and competency-based workforce classification has not been established yet,20 and this makes that cross-location comparative workforce studies still needing to be based on professional labels. Finally, the official existence of PT assistants was negatively associated with the PT and OT supply at a 95% confidence level, although not after Bonferroni correction. This negative association is not surprising as the presence of assistant professions contributes to meet population needs in addition to, and often in complement of, the main professions; hence it may interfere with the demand for the latter. This paper has several limitations: We had comparable, complete data only for 35 HICs; this reduced the statistical power and may have accounted for the inability to detect other relevant associations. Moreover, broad ecological trends may not apply to all individual HICs, as shown by the Singapore case. The trends should be understood only for the context of the HICs assessed, and not for the context of other countries, such as many LMICs – where large unmet rehabilitation needs exist and the development of the rehabilitation workforce is in its infancy.10 The results should not be inferred to represent physical rehabilitation more generally. In our data, proportions of PTs and OTs varied greatly from a 55%-45% PT-OT distribution (Israel) to 98%-2% , as the roles of these professions often partially overlap.16 In this study, we did not collect or analyze data on which roles do PT and OT professionals have in each country to understand these differences. Nonetheless, the fact the we have combined the supply of both professions into a composite supply indicator can fade the impact of these different distributions into the study’s results. The indicator of the physical rehabilitation workforce supply only included data on PTs and OTs, while other professions  would be relevant as well. In addition to data from other rehabilitation professions, we did not include data on generalist health professions, such as medical doctors or nurses, which could be used for comparative purposes. Yet, we suggest that this study on the historically neglected rehabilitation workforce can model others to examine whether need indicators are independent predictors of supply for other specific health workforces, or the health workforce overall. Also, unlike for PTs, we did not have an indicator on whether the OT supply per country was based on authoritative data or on an estimate. Moreover, the data for the PT and OT workforce supply was restricted to that reported from national associations of the respective professions to the international federations or confederations regarding the number of practicing professionals, while other mechanisms  and broader supply data  could, if available, also be informative as well as add robustness to the findings. Also, we did not had data pointing for the percentage of PTs or OTs working in the public or private sector. It is noteworthy, though, that items on the level of domestic government spending in healthcare did not prove to be significant factors in this study.14; however, that set of conditions cannot be considered a fixed standard and can evolve with scientific advances. The composite indicator of need was based on current data extracted from the GBD 2017, the largest global epidemiological study to date; however, that data was based on diseases and their sequalae, while physical rehabilitation addresses functional limitations which account for environmental factors as well. Similarly, the set of conditions used for computing the need indicator was based, for example, in the findings of existing systematic reviews on the effectiveness of the physical rehabilitation interventions PT and OT workforce supply is highly variable across HICs. This variability is not accounted for by a composite indicator of population need but rather by financial factors and population size. These broad ecological findings, along with country-specific data, should inform the development of deliberate physical rehabilitation workforce policies and planning, whether needs-based or not. All data used are in the public domain. Authors declare that they have no competing interests. TJ: Conception and design; acquisition of data; analysis and interpretation of data; drafting the manuscript; critical revision of the manuscript for important intellectual content; statistical analysis. ML: Conception and design; analysis and interpretation of data; critical revision of the manuscript for important intellectual content. HH: Conception and design; analysis and interpretation of data; critical revision of the manuscript for important intellectual content. GD: Analysis and interpretation of data; critical revision of the manuscript for important intellectual content. GK: Analysis and interpretation of data; critical revision of the manuscript for important intellectual content. IF: Conception and design; analysis and interpretation of data; critical revision of the manuscript for important intellectual content; statistical analysis.1Global Health and Tropical Medicine & WHO Collaborating Center on Health Workforce Policy and Planning, Institute of Hygiene and Tropical Medicine - NOVA University of Lisbon, Lisbon, Portugal. 2School of Medicine, Duke University, Durham, NC, USA. 3Duke Global Health Institute, Duke University, Durham, NC, USA. 4Physical Medicine and Rehabilitation Service, Durham Veterans Administration Medical Center, Durham, NC, USA. 5Division of Geriatrics, Department of Medicine, Duke University Medical Center, Durham, NC, USA. 6Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore.Supplementary file 1. Raw Data (Extracted) Per Country.Click here for additional data file.


As the likelihood and impact of cyber-attacks continue to grow, organizations realize the need to invest in specialized methods to protect their digital data and the information they circulate or manage. Due to its broad use, game theory has evolved into a concept that can be applied practically while analyzing and modifying existing cyber protection methods to arrive at the best possible conclusions. This study presents an innovative hybrid model that combines game theory and advanced machine learning methods for adaptive cyber defense strategies. Specifically, a repetitive game methodology is implemented to analyze cyber-attacks and model behaviors and study how defenders and attackers make decisions in a competing field. Based on Bayesian inference, the proposed method can predict the next steps in the game to produce the appropriate countermeasures and implement the best cyber defense strategies that govern an organization. The suggested system introduced to the academic literature for the first time was successfully tested in a particular application scenario involving the digital music industry and coping with impending cyber-attacks. As the cyberspace landscape evolves rapidly, a dynamic framework emerges in which very delicate balances are observed to make optimal decisions. The asset, information, and data values that modern organizations must manage constantly increase. New cyber-attack techniques are continually developing while existing technological defense systems age, making active defense strategies resilient. Furthermore, economic changes, institutional reorganizations, consumer trends, and legal and regulatory compliance requirements all impact decision-making and the overall development of sound defense strategies for an organization or company. To maintain its competitive advantage, the organization in question will need to continuously improve its defense strategies, which will be based on ongoing knowledge and utilization of the cyber threat landscape . An accuGame theory  can be uThis study presents applications of game theory and advanced machine learning methods for adaptive cyber defense strategies in the digital music industry. An innovative application of a repetitive game methodology for cyber-attack analysis is proposed; using Bayesian inference , the nexThe literature on game theory for adaptive cyber defense approaches is extensive, whether at the network level, where we must deal with massive amounts of raw data or at the strategy level.In 2015, Laszka et al.  developeSchlenker et al.  exploredNguyen et al.  conducteAlpcan and Basar , in 2010Hemberg et al.  presenteMany cyber-attacks follow a pattern built on repeating tactics or procedures over time. Infrastructure vulnerability control strategies, for example, can compete with current defensive systems and change their applications over time. In this sense, attackers and defenders engage regularly, and these interactions may be depicted using repetitive games, which are a type of dynamic game . The conn} is the set of players, Xi is the set of the player's ί pure strategies, and u is its performance function. Assume that this stage game is repeated T times, where T is finite or infinite. Each repetition takes place over a period. A typical time (or stage) is denoted by ί, where ί = 1, 2, ..., Τ. The interaction evolves as follows [(1)x1=, where the pointer symbolizes the player and the exponent symbolizes the stage (time period). The action x11 belongs to the set Xi, i ∈ N. Each player has been informed afterward of the choices of the other players. The performance of player i in this period isIn period 1, players simultaneously select actions, which we symbolize as (2)x2=. Each player has been informed afterward of the choices of the other players. Player's i odds areIn period 2, players choose at the same time actions (3)T, players choose actions xT=. The player's odds areIn period (4)T is finite, the interaction is complete (at the end of period T). Otherwise, the game continues in perpetuityIf The starting point for modeling the proposed system is a static game of the following format: follows , 17:(1)Iδ is the discount rate of an individual [δ is to 0, the less the individual values a future versus a present performance. In other words, the smaller the δ is, the less the person is interested in the future or the more impatient he is. Conversely, the higher the δ (the closer it is to 1) is, the more a person values a future performance or is more patient [In the repetitive game, we suggest each player earns a sequence of payoffs (one payoff for each period). This yield sequence is assumed to be valued using the discounted sum of the sequence terms. The term discount expresses the assumption that a person does not value current and future returns equally. Parameter dividual . The clo patient –21.hT=. If the discount rate of player i is given by the parameter δi ∈ , then the discounted sum of the payoffs of player i isLet a finite terminal story h∞=. In this case, the discounted sum of player's payoffs isLet now an infinite terminal story T, instead of the discounted sum of the odds, we use the discounted average of the player's odds as a valuation function:In the case of infinity i obtains the sequence of odds . We define a number c such that i is indifferent between the series of yields  and the sequence . So, we take the following relation [Based on the relation, player relation :(8)Vi=∑tHowever, it is true thatConsequently, we haveδi)Vi is the discounted average of the yield sequence . The functions Vi and (1 − δi)Vi express the same preferences since one is a positive monotonic transformation. Thus, the set of all terminal stories is the set of all sequences [The term i evaluates the terminal history h∞ based on the function:So, player G∞(δ).So, we have the repetitive game A rule that dictates the player's behavior in response to any and all scenarios is an example of a strategy. Consequently, a single-player strategy is a guideline for picking actions at each stage (repetition) of the stage game as a function of previous decisions when playing a game that features observable actions and is repetitive. To be more exact, the energy that the player will pick at each narrative stage is determined by the strategy used in a game with just one player and repeated steps. The action must be feasible; that is, it must belong to all the available options of the gaming stage , 25.Odds pairs corresponding to the four pairs of clear strategies are feasible (in the sense that there are strategies that generate specific returns). It should also be noted that all convex combinations of two or more yield pairs of pure methods constitute achievable yields (using mixed strategies) , 26.In general, the total possible odds of the stage game are given by the quadrilateral in In order to model the proposed system, a specialized threat scenario was implemented with an application study in the music industry. This was done because the large number of visitors combined with the enormous amounts of music content spent on a daily basis creates a new landscape of threats, in which the clear strategies for cybersecurity need to be rearranged on an ongoing basis. According to this logic, they frequently employ advanced techniques, including zero-day attacks, to launch attacks on music streaming platforms that modern cybercriminals have targeted , 27, 28.N, i∈N}, such thatu1∗, u2∗,…, un∗) is the payoff vector of a Nash equilibrium of Γ  with average odds Then, there is a perfect subgame balance for the game To prove the above scenario, we will assume that the vector rategies , 10.u1∗, u2∗,…, un∗) of Γ are derived from the strategy vector .Suppose that the equilibrium returns ((1)i = 1:i selects an action player Stage (2)i > 1:i selects an action If the result in the previous stages 1, 2, ..., t-1 is i selects an action xi∗In all other cases, player Stage We consider the following firing strategy:We will examine the players' motivations for adopting or not the above strategy.i if all other players adopt the firing strategy. We must determine the optimal response of i in each period where it has observed a result Let us look at player i will take if it observes in a period t that in the previous period t-1 a result other than i knows that, in period t, the other players will choose the actions xi−∗ and that this will be done in perpetuity (because they follow the firing strategy). Therefore, the optimal reaction of 1 is to choose xi∗ in perpetuity.It should be recorded the actions that i will do in those periods for which history contains only the result i chooses to deviate from the energy xidd, is what solves the problem.Let us now see what player In particular,i during the deviation period isThe yield of xi−∗, after noticing the choice xid of i. The punishment period of i will therefore begin. Given this, the optimal response of i is to select the energy xi∗. Thus, from the period following the deviation to perpetuity, i will have a payoff of ui∗ per period. Its average discounted return from the breach is, therefore,From the next period, the other players will start choosing i, after each story that contains only i will continuously gain i in this case isIf, on the contrary, i will select Therefore, player If the following inequality relations are valid,And soThe possible payoffs that exceed the Nash payoffs are shown in Next, to determine which value can best estimate the random variable, we apply Bayesian inference to create a loss function, which will measure how wrong the estimate is, that is, how different the estimation of the parameter is from its actual price. This means that the goal is for the value of the estimate to minimize the loss function. For example, in the absolute error loss function, underestimation and overestimation of the parameter are punished in the same way, depending on the deviation of the estimate. In contrast to the preceding statement, the linear loss function penalizes underestimation with a different weight than overestimation.L is the loss function and δ = δ(x) is the decision rule, the hazard function of the decision rule δ is mathematically expressed asThe evaluation of the decision rules is done through the risk function, which is defined as the average value of the loss function. If u(θ). So, the Bayesian risk is defined as [In the Bayesian approach, it is possible to balance the risk function of each decision rule, based on ex-ante personal opinion, through fined as –31(25)BRδ, as a function of the loss of a square error, is equal toThe decision rule that minimizes Bayesian risk is the Bayesian rule. In particular, the Bayesian risk of decision rule x) is a nonnegative function, we are interested in minimizing theSince the margin function g(δ(x) whenThe above function is minimized for So, through a hypothesis check, we can determine the correctness of a hypothesis that concerns an action without dealing with estimating the possible values of the strategy. Based on this view, it is possible to predict the future prices of the process as, through the ex-post distribution, the forecasting process is immediate and accurate.x = x1, x2, …, xn, it is desirable to predict the future observation y, and it is necessary to calculate the a posteriori distribution of prediction π(y|x). For the mathematical calculation of the ex-post distribution, the mathematical analysis of the ex-prediction distribution g(x) is required:Assuming that, for a random sample of observations f(x|θ), with the ex-ante distribution u(θ). Thus, based on the above procedure, the mathematical definition of the ex-post prediction distribution π(y|x) will be made:Observing the equation, it is easy to see that the integral contains the product of the probability function f. It should be noted that this time the shared distribution function is bound to the observed data. Re-applying the Bayesian theorem, we conclude that the ex-post distribution of prediction is again equal to the product of probability f(y|θ), but this time, with the ex-post distribution p(θ|x), this is completed for the variable θ.The probability function of the following observations is equal to the integral of the joint probability function f, we came to the probability function if all a posteriori information originates from the parameter θ.The effect of the ex-post information is therefore apparent. It should be noted that, from the probability function To prove the validity of the methodology described above, we will make the assumption that we will count the number of privilege escalation attacks made against a randomly chosen account on the music streaming platform that is the focus of the current example.θ), θ ∈ Θ= , i.e.,Suppose that the number of specific attacks over a period follows the “Poisson” distribution , where a, β > 0; quantities are known as a function of probability density:Suppose that the ex-ante distribution of Therefore, the distribution margin isθ isTherefore, the a posteriori distribution of θ is [From the above relation, it becomes clear that the a posteriori distribution of θ is (37)GammaGamma distribution was expected since the Gamma distribution family, where the ex-distribution belongs, is conjugated to the Poisson distribution.The ex-post distribution following the Gamma distribution is [The ex-post average value for the above ution is , 32, 33(r ~ Poisson(θ) be a new independent observation. The equation gives the forecast distribution:Let el it is , 35(40)πrameters –38:(41)∑This research offered an original and forward-thinking application of game theory and cutting-edge machine learning methods for adaptive cyber protection measures. It suggested a methodology based on game theory, which concerns the study of elements that characterize situations of competitive interdependence with an emphasis on the decision-making process of more than one decision maker. We make the assumption that every player is informed of the equilibrium tactics that the other players will use and that no player has anything to gain by merely altering the strategy that he uses. Therefore, in order to figure out which value can provide the most accurate estimation of the random variable, we use Bayesian inference to devise a loss function. This function will measure how inaccurate the estimate is, or more specifically, how far off the estimation of the parameter is from the actual price. This indicates that the objective is to have the value of the estimate be as low as possible concerning the loss function.Specifically, the study of features that characterizes conditions of competitive interdependence includes the opponents. To be more specific, a methodology based on a repeated game is used to examine cyber-attacks and model behaviors and research how defenders and attackers make decisions in an environment where they compete. The unique approach developed can forecast the future moves in the game to generate the proper countermeasures and apply the most acceptable cyber defense tactics that govern a company. This ability is based on the use of Bayesian inference, which is a type of statistical inference. The suggested system was tested with great success in a particular application scenario in the digital music sector and how to cope with upcoming cyber-attacks. The testing was successful on both fronts.A crucial step in further developing the proposed model is the further investigation of how they can adapt the method parameters to processes of modern and asynchronous change of the initial parameters of the evaluators. This is one of the processes that will further the development of the proposed model. As a result, the expansion and empirical exploration of the characteristics of the method estimators in finite samples, which call for the use of Monte Carlo simulations, is also a vital component of the proposed system's evolutionary parameter.


The 21st century is the information age. The ever-changing information technology not only affects the development of the global economy, but also has an important impact on the field of education and personnel training. Under the influence of information technology, the way people acquire, impart, and evaluate knowledge has changed greatly. The educational concepts, models, and methods of the new era are fundamentally different from traditional education, which provides new opportunities and new challenges for the education and teaching work of contemporary teachers. This paper aims to discuss the application of augmented reality technology in volleyball teaching, and give an effective method for AR to be applied to volleyball teaching. In this paper, the existing AR teaching system has the problem of poor transmission rate and cannot cooperate with volleyball teaching well. Therefore, a wireless communication auxiliary algorithm based on intelligent reflective surface is proposed. And the current situation of volleyball teaching is investigated and analyzed. And in response to the survey results, 78% of the students supported teachers in applying AR technology to assist teaching in volleyball teaching classes. This fully shows that there is still a lot of application space for AR technology in current volleyball teaching. With the rapid development of modern education, information technology has become an indispensable part of the field of education and an important symbol of educational modernization. High school volleyball has the characteristics of comprehensiveness and regionality, abstract knowledge, and great difficulty in learning. The application of information technology to volleyball teaching has become the trend of the times. Based on reading a large number of related literatures, this paper clarifies the research topic and summarizes the background, significance, and research status of the application of augmented reality technology in high school volleyball teaching. Since the early domestic researches were mainly focused on children's education and higher education, factors such as the psychological laws of middle school students, the hardware facilities of ordinary middle schools, and the curriculum standards of middle schools were not well considered. Therefore, it is difficult to promote and popularize the results of early research in secondary education. Therefore, this paper is based on the teaching practice of high school volleyball, supported by constructivism theory, situational learning theory and audio-visual teaching theory, designed a research plan and carried out teaching experiments, and applied augmented reality technology to the teaching practice of high school volleyball.Under the background of the times and the requirements of new curriculum standards, it is hoped that through this research, volleyball teachers can improve their ability to effectively use information-based teaching resources, especially the ability to effectively use AR technology. It also hopes to provide reference for volleyball teachers to transform teaching methods through AR technology, promote the transformation of volleyball teaching mode, cultivate students' information literacy, enhance students' volleyball thinking, change students' learning behavior, and improve students' volleyball practice ability.The innovation of this paper is that: design teaching cases according to the teaching status and technology application status reflected by the survey data and carry out teaching experimental research on this basis. Combining teaching theory and teaching practice, this paper analyzes the effect of augmented reality technology in volleyball teaching from three aspects: volleyball test scores, student questionnaires, and teacher interviews. This paper points out the main factors that restrict the wide application of augmented reality technology in volleyball teaching, and provides real data and reference for front-line volleyball teachers to apply augmented reality technology to assist teaching. However, due to the small research scope and limited research time, the research conclusions of this paper also have certain limitations and one-sidedness. It is believed that with the rapid development of education modernization, the application of augmented reality technology in high school volleyball teaching will become more and more extensive and mature.As one of the three major balls, volleyball is widely loved. In particular, the spirit of the Chinese women's volleyball team has stimulated people's enthusiasm for volleyball, and there are many teaching and research on volleyball. The Batez study investigated the impact of a Teaching Play (TGfU) model implemented in physical education classes on volleyball skills and enjoyment of middle school students. The findings demonstrate the effectiveness of the short-term TGfU model 12 lessons) in improving volleyball skills in an educational setting. He also emphasized the importance of having fun in these classes compared to traditional physical education classes 2 lessons. Wang anThe research on augmented reality is also a current hot issue. AR is widely used, and there are many problems to be solved at the technical level, and there are many applications in teaching. Research by Paraskevaidis and Fokides presented the results of a pilot project using 360 videos to teach students basic volleyball skills . Turkan AR technology is a technology with interactive functions that superimposes virtual information into the real environment with the support of related equipment, so that the virtual information and the real environment are presented synchronously in the same time and space. It is related to VR technology but it is different, as shown in AR technology is built on the basis of reality, and it is still the real world at all. Its simple schematic diagram is shown in As shown in With the development of modern educational technology, the application of Augmented Reality (AR) technology has also begun to penetrate into the field of education. The American New Media Alliance has twice listed AR technology as a new technology that will have an important impact on modern education in the Horizon Report. AR technology has accumulated a lot of experience worthy of reference in various learning modes such as game learning and interactive learning, and successfully and effectively integrated digital teaching resources with the real world. And it produces educational products such as popular AR books, AR educational software, and AR educational games. It can be seen that the rise of AR technology has laid a good foundation for its application in the field of education. AR technology can superimpose abstract volleyball knowledge, especially the larger space-time scale, into the real environment, and students can observe, experience, and understand the knowledge immersive in the augmented reality world. It creates an advantage condition that other technologies cannot match for volleyball teaching. Facing the rapid rise of AR technology, volleyball teachers should take a positive attitude to meet the opportunities and challenges that AR technology brings to volleyball education. The application of AR in teaching is shown in With the rapid development of AR technology, there are more and more devices supporting AR technology, including professional equipment such as AR glasses, AR helmet, and AR projector, as well as smart mobile devices such as mobile phones and tablet computers that realize augmented reality functions through camera functions. Among the above equipments, due to the high price of professional equipment, they have not been widely used. Therefore, AR technology based on smart mobile devices such as mobile phones and tablet computers has become the most commonly used and mainstream augmented reality method due to its easily acceptable price and good augmented reality effects. It can be seen that it is not difficult to apply AR technology to education and teaching. Only a smartphone or tablet with a camera function and AR application software can effectively complete classroom teaching, so that students can get AR learning experience in the classroom, as shown in Since the most common and mainstream augmented reality method is realized through mobile devices such as mobile phones and tablet computers, there are many AR education products developed and designed based on mobile devices. Thanks to the development and popularization of smart mobile devices and network communication technology, coupled with the increasingly mature AR technology, teachers of various disciplines can now choose AR products suitable for their classrooms from the rich and diverse AR education software to assist teaching. In terms of middle school volleyball teaching, more mature products have been developed: “Understanding Junior High School Volleyball” for junior high school volleyball and “AR Middle School Globe” for high school volleyball. In addition, teachers can also try to independently develop and create simple AR materials according to teaching needs and teaching material content . CurrentAR technology can transform abstract content into concrete images due to its good interactivity, immersion, and virtual-real connectivity. The application of AR technology is of great significance to overcoming the above difficult knowledge and cultivating students' spatial imagination. It can be seen that the application scope of AR technology in volleyball teaching is very broad, and the application significance is very significant .Although the global deployment of fifth-generation mobile communications (5G) has just started, industry and academia have begun to look to the post-5G future, such as sixth-generation mobile communications (6G), which are designed to meet higher requirements than 5G. 6G requires higher throughput, higher energy efficiency, wider connectivity, and higher reliability and lower latency than 5G. However, the existing 5G technologies are mainly aimed at the three major application scenarios of enhanced mobile broadband (eMBB), ultra-reliable and low-latency communication (URLLC), and massive machine communication (mMTC), which may not fully meet the requirements of 6G , 15. TheIntelligent Reflector (IRS) can realize intelligent control of wireless propagation environment, provides an important technical solution to solve the above problems, and has become a key candidate technology in 6G. A typical IRS is a plane composed of a large number of low-cost, almost passive reflectors. Each reflector can independently control changes in the amplitude and/or phase of the incident signal. By densely deploying IRS in a wireless network and intelligently coordinating its reflections, the wireless channel between transmitter and receiver can be flexibly controlled to achieve the desired signal propagation environment. Thereby, it provides a new method to fundamentally solve the problem of wireless channel fading and interference, and it is possible to realize a huge leap in the throughput and reliability of wireless communication network.π. By setting the corresponding bias voltage through the IRS controller, the phase shift of each reflector can be adjusted independently. In order to control the amplitude of the reflection coefficient, a variable resistance load can be used in the design of the reflection element, and the amplitude and phase shift of the inverse element can be changed by changing the resistance value. Therefore, the above circuit needs to be effectively integrated.To address the above two problems, this chapter proposes a novel location-based multi-IRS-assisted multiuser system framework. The proposed location information-based design framework has the following three advantages over existing design frameworks, which require complete CSI and consume a large amount of pilot overhead. First, location data can be easily collected via GPS, significantly reducing pilot overhead. Second, unlike instant CSI, location information changes slowly, so it does not need to be constantly updated. In addition, since only a limited amount of location data needs to be transmitted between the base station and the IRS, only a small-capacity feedback link is required, thereby reducing the installation cost of the IRS. In the following introduction, the abbreviations and symbols involved are shown in Tables K single-antenna users, each assisted by an IRS with M reflectors. The BS is connected to the IRS via a low-capacity hardware link to exchange information (such as CSI and phase shift information) with each other.As shown in Using Rice fading to model the channels from BS to IRS and from IRS to users:Among them,CN, αB2I,m represents large-scale fading, vB2I,m represents the Rice factor, and the LoS component Formula  represenThe effective departure angle can be expressed asdBS represents the distance between the adjacent antennas of the BS. Similarly,The effective departure angle is expressed asdIRS represents the distance between adjacent reflectors, cos  θB2Ia,msin  θB2Ia,m are the elevation and azimuth angles of the mth IRS, respectively. Also, assume:n-th element of the array response vector a(ϑ) and the l-th element of b(ϑ) are given by the following two equations, respectively,The mth IRS to the kth user is expressed asSimilarly, the channel from the Among them, the LoS component isIt can be expressed as:The BS sends a signal:Among them,Formula  represenkth user can be expressed asThe signal received by the nk ∈ CN represents AWGN, and the phase shift matrix of the mth IRS isAmong them, Among them,Formula  represenQuestionnaire survey method: A questionnaire about volleyball learning and the application of AR technology in high school volleyball teaching was distributed in the No. 6 Middle School in K City, to investigate the basic situation of students' volleyball learning and the application status of AR technology in high school volleyball teaching.Interview method: According to the interview outline, the volleyball teachers in K city were interviewed, and from the perspective of teachers, the current situation of teachers using information technology to assist volleyball teaching and the application status of AR technology in high school volleyball teaching were investigated.There are 15 questions in the questionnaire, all of which are multiple-choice questions. The main survey contents are volleyball learning interest (questions 1-2); learning difficulty (questions 3–5); classroom atmosphere (questions 6-7); teaching methods (questions 8–11); teaching effect (question 12); students' understanding of AR technology (question 13); the application of AR technology (question 14); students' attitude towards the application of AR technology in the classroom (question 15).There are 6 questions in the interview outline. The main content of the interview is the current situation of high school volleyball teaching, including teachers' teaching methods, teaching methods, understanding of AR technology, application of AR technology, and attitude towards the application of AR technology in teaching.The questionnaire survey is to randomly select 100 students in K city to distribute paper questionnaires. A total of 100 questionnaires were distributed in this survey, and 98 were recovered, of which 95 were valid questionnaires. With the help of SPSS software and EXCEL software to carry out statistics and analysis on the results of the questionnaire, the analysis results are as follows.Questions 1-2 mainly focus on volleyball learning interest. The survey results show that among the students surveyed, 28% of the students are not very interested in volleyball, and 52% of the students are more interested in volleyball, 12% of students have no interest in volleyball, while only 8% are very interested in volleyball. Among the factors that affect students' interest in volleyball lessons, the volleyball classroom atmosphere is the most influential factor with 44% of paired interest in volleyball learning. Secondly, the teaching method of teachers accounted for 30%, the content of teachers' teaching accounted for 20%, and some other factors such as: the degree of love for volleyball teachers, the amount of homework, and the difficulty of homework. The above data shows that most students are highly interested in volleyball learning, and only a small number of students are not interested in volleyball. Compared with the teaching content, students are more concerned about the classroom atmosphere and teachers' teaching methods. In addition, students' evaluation of teachers and after-school homework also constitute factors that affect students' interest in volleyball learning. The details are shown in Tables Questions 6-7 mainly focus on the volleyball classroom atmosphere. The survey results show that 46% of the students ideally have a more active volleyball classroom atmosphere, 41% of the students hope that the volleyball classroom is very active, 9% of the students like the classroom atmosphere of occasional communication, and only 4% of the students want the volleyball classroom to be very quiet. In fact, only 18% of the students expected the volleyball classroom atmosphere to meet their expectations. 58% of the students believed that the volleyball classroom atmosphere was sometimes what they expected, and 24% of the students believed that the current volleyball classroom atmosphere was not what they expected at all. The above data shows that students prefer a relatively active classroom atmosphere to a very active or very quiet classroom atmosphere. The actual volleyball classroom atmosphere is relatively dull and quiet, and students' expectations can only be met occasionally, which also provides a good opportunity for the application of AR technology in teaching, as shown in Tables Question 13 mainly surveys students' understanding of AR technology. The survey results show that 54% of students have never used AR technology in their life, 40% of students have used AR technology occasionally, and only 6% of students often use AR technology. The above data shows that there are more students who are infrequently exposed to AR technology than those who are often exposed to AR technology, and most students lack understanding of AR technology. Only a very small number of students often use AR technology and mainly understand the technology through AR games, and have not used AR technology in their studies. It can be seen that although AR technology has developed very maturely and is widely used in various aspects, AR technology is still a relatively unfamiliar technology to students in K City. On the one hand, the application of new technology can help teachers solve volleyball teaching problems and improve teaching efficiency. On the other hand, it is also helpful to increase students' interest in volleyball learning and mobilize students' enthusiasm and initiative in learning, which is also one of the necessary reasons for AR technology to be applied to volleyball teaching.Question 14 mainly investigates the application of AR technology in volleyball teaching. According to the survey results, 94% of the students chose that teachers have never used AR technology in volleyball lessons, 6% of students chose teachers to occasionally use AR technology in volleyball lessons, and no students chose teachers to use AR technology frequently. The above data shows that the application of AR technology in the current volleyball classroom is very small, and only some teachers occasionally try to use it. It can be seen that the application status of AR technology in the current volleyball teaching is not ideal, and the specific reasons will be further understood through interviews with teachers.Question 15 mainly surveys students' attitudes towards the application of AR technology in the classroom. The survey results show that 78% of students support teachers' application of AR technology in volleyball classes to assist teaching, 13% of students think it doesn't matter, and 9% of students do not support teachers' application of AR technology in class. The above data shows that most students have a positive attitude towards the application of AR technology, which creates a good atmosphere for the application of AR technology, as shown in In order to ensure the smooth application of AR technology in volleyball teaching, it is necessary to improve technical support first, such as multimedia resources and the introduction of advanced AR technology. First of all, it is necessary to introduce foreign advanced hardware equipment and development platforms, so that students have a sense of “reality” in the electronic environment. Therefore, it is necessary to introduce foreign advanced technology to improve the equipment platform for information collection, processing, and display. Secondly, the design should be “usefulness, usability, and emotionality.” The application of AR technology in volleyball teaching should design a concise interface and operation process. So, it can make the combination of virtual and reality, and the combination of AR technology and traditional classroom teaching bring vivid interactive emotional experience. From the perspective of visual elements, the use of augmented reality technology to break through the visual expression of traditional classroom teaching, and replace it with a dynamic, virtual and realistic visual image to express the language of information. In terms of auditory elements, real and natural sounds are applied in teaching with the help of augmented reality technology, so as to endow volleyball teaching with vitality and lasting vitality.In China, AR teaching research is in its infancy. Although various disciplines have achieved different degrees of research results in related fields, the current research in various fields is still immature, and the majority of educators still need to continue to explore and practice to provide useful guidance for the application of AR technology in the field of education. This paper firstly investigates the current status of volleyball teaching and the application status of AR technology in volleyball teaching. Firstly, this paper investigates the current situation of volleyball teaching and the application of AR technology in volleyball teaching, and designs teaching cases according to the investigation results, and then carry out teaching experimental research through the method of quasiexperimental research, and evaluate the effect of AR technology applied to high school volleyball teaching in multiple ways, aiming to provide reference and reference for the application of AR technology in high school volleyball teaching.