Epidemiology of alopecia areata, ophiasis, totalis and universalis: A systematic review and meta-analysis

Abstract Background Alopecia areata (AA) is a common, autoimmune, alopecia with heterogeneous severity and distribution. Previous studies found conflicting results about AA epidemiology. Objective Determine the prevalence, incidence and predictors of AA, alopecia totalis (AT), ophiasis (AO), and universalis (AU). Methods A systematic review of all published cohort and cross-sectional studies that analyzed AA and its subtypes. MEDLINE, EMBASE, LILACS, Scopus, Cochrane library and GREAT were searched. At least 2 reviewers performed study title/abstract review and data extraction. Random-effects meta-analysis was used owing to significant heterogeneity (I2=99.97%). Results Ninety-four studies met inclusion criteria. The pooled prevalence (95% confidence interval [CI], n) of AA overall was 2.11% (1.82-2.42%, n=302,157,365), with differences of population-based (0.75% [0.49-1.06%], n=301,173,403) and clinic-based (3.47% [3.01-3.96%], n=983962) studies. The prevalences of alopecia totalis, ophiasis, and universalis were 0.08% (0.04-0.13%, n=1,088,149), 0.02% (0.00-0.06%, n=1,075,203), and 0.03% (0.01-0.06%, n=1,085,444), respectively. AA prevalence [95% CI] increased over time ( 2009: 3.22% [2.59-3.92%]; P Conclusions AA affects 2% of the global population. AA prevalence is lower in adults than children, is increasing over time, and significantly differs by region.