OBJECTIVES: Alopecia areata (AA) is an autoimmune disease that has an underlying immuno-inflammatory pathogenesis and is characterized by nonscarring hair loss of the scalp, face and /or body. A comprehensive understanding of global epidemiology of AA is needed for future disease management. A systematic literature review was conducted to identify epidemiological rates and frequency of AA and associated comorbidities across US, Europe, and Asia.

METHODS: Studies from January 2010-October 2021 reporting incidence or prevalence of AA were identified in EMBASE, MEDLINE, and Cochrane databases. Additional manual searches were performed for abstracts published at relevant congresses (2019-2021).

RESULTS: 97 publications for 96 original studies were selected, with majority being retrospective studies [comprised of 48 (50%) cohort studies; 29 (30%) database/registry], followed by prospective observational studies [n=13 (14%)], and cross-sectional surveys [n=6 (6%)]. Point prevalence for AA varied from 0.04% to 6.7% (21 studies); lifetime prevalence was between 2.5% to 13.8% (3 studies). The prevalence over a period of up to 5 years varied from 0.42% to 4.95% (19 studies). Among US studies, period prevalence ranged from 89.0 to 122 per 100,000. One study (US claims database) reported prevalence rates specifically in children and adolescents (≤18 years) with overall prevalence of 0.05%. Estimated prevalence rates over 0-5 years for alopecia ophiasis, alopecia totalis, and alopecia universalis were 0.01-0.07%, 0.08-0.15%, and 0.01-0.07%, respectively. Annual incidence of AA was reported in 9 studies, ranging from 2.53 to 26 per 100,000. Comorbidities in AA were reported in 10 studies, in which atopic dermatitis, obesity, depression, and thyroid diseases were the most frequently reported.

CONCLUSIONS: Published incidence and prevalence rates reported for AA are highly variable, partly due to vastly different data sources by age-group, comorbidities, and region. Future research is needed to obtain more precise estimates for these epidemiological rates across key strata.