Epidemiology and burden of alopecia areata: a systematic review

Background: Alopecia areata (AA) is an autoimmune disorder characterized by patches of non-scarring alopecia affecting scalp and body hair that can be psychologically devastating. AA is clinically heterogenous, and its natural history is unpredictable. There is no preventative therapy or cure. Objective: The objective of this study is to provide an evidence-based systematic review on the epidemiology and the burden of AA. Methods and selection criteria: A search was conducted of the published, peer-reviewed literature via PubMed, Embase, and Web of Science. Studies published in English within the last 51 years that measured AA's incidence, prevalence, distribution, disability-adjusted life years (DALYs), quality of life, and associated psychiatric and medical comorbidities were included. Two authors assessed studies and extracted the data. Results: The lifetime incidence of AA is approximately 2% worldwide. Both formal population studies found no sex predominance. First onset is most common in the third and fourth decades of life but may occur at any age. An earlier age of first onset corresponds with an increased lifetime risk of extensive disease. Global DALYs for AA were calculated at 1,332,800 in 2010. AA patients are at risk for depression and anxiety, atopy, vitiligo, thyroid disease, and other autoimmune conditions. Conclusion: AA is the most prevalent autoimmune disorder and the second most prevalent hair loss disorder after androgenetic alopecia, and the lifetime risk in the global population is approximately 2%. AA is associated with psychiatric and medical comorbidities including depression, anxiety, and several autoimmune disorders, and an increased global burden of disease.