National, Regional, and Global Epidemiology of Alopecia Areata: A Systematic Analysis Based on Modeling Study

Background Alopecia areata (AA) is a prevalent nonscarring hair loss disease affecting the scalp and body hair. However, previous studies have reported conflicting findings regarding its epidemiology. We aimed to quantify the global, regional, and country‐specific estimates of AA epidemiology. Methods We conducted a comprehensive systematic review of published studies reporting on the incidence and prevalence of AA. We searched four electronic databases from January 1, 1992 to October 20, 2023: PubMed, Embase, Web of Science, and China National Knowledge Infrastructure. A Bayesian hierarchical linear mixed model was employed to determine the epidemiological estimates, accounting for variations in regions, diagnostic types, and age groups. Results 73 studies met the inclusion criteria. The incidence varied across different geographical locations and age strata. The overall point prevalence and diagnosed population of AA were estimated at 1.93% (0.17%–5.91%) and 15.05 million people, respectively. The United Kingdom, Saudi Arabia, Iraq, and Egypt exhibited the highest prevalence. Globally, approximately 10.29 million adults and 4.76 million children had AA, with a prevalence of 1.98% (0.17%–6.07%) for adults and 1.83% (0.16%–5.58%) for children. Women were more likely to suffer from it. The global prevalence in females was 2.25% (0.20%–7.03%), affecting 8.69 million individuals, whereas for males, the estimates were 1.62% (0.14%–4.80%), impacting 6.36 million individuals. Variations in the epidemiological results might also stem from the chosen method of prevalence estimation. Conclusion Epidemiological data for AA were absent in 89.1% of countries globally. The epidemiology varied across gender and age groups and was unevenly distributed among geographical regions.