The epidemiology of alopecia areata: a population-based cohort study in UK primary care

Background: There is a lack of population-based information on the disease burden and management of alopecia areata (AA). Objectives: To describe the epidemiology of AA, focusing on incidence, demographics and patterns of healthcare utilization. Methods: Population-based cohort study of 4·16 million adults and children, using UK electronic primary care records from the Oxford-Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC) network database, 2009–2018. The incidence and point prevalence of AA were estimated. Variation in AA incidence by age, sex, deprivation, geographical distribution and ethnicity was examined. Patterns of healthcare utilization were evaluated in people with incident AA. Results: The AA incidence rate was 0·26 per 1000 person-years. AA point prevalence in 2018 was 0·58% in adults. AA onset peaked at age 25–29 years for both sexes, although the peak was broader in females. People of nonwhite ethnicity were more likely to present with AA, especially those of Asian ethnicity [incidence rate ratio (IRR) 3·32 (95% confidence interval 3·11–3·55)]. Higher AA incidence was associated with social deprivation [IRR most vs. least deprived quintile 1·47 (1·37–1·59)] and urban living [IRR 1·23 (1·14–1·32)]. People of higher social deprivation were less likely to be referred for specialist dermatology review. Conclusions: By providing the first large-scale estimates of the incidence and point prevalence of AA, our study helps to understand the burden of AA on the population. Understanding the variation in AA onset between different population groups may give insight into the pathogenesis of AA and its management. What is already known about this topic?: Alopecia areata (AA) is a common cause of nonscarring hair loss associated with psychological morbidity. Large-scale population-based information on the disease burden and clinical management of AA is lacking. What does this study add? In the largest population-based study of AA to date, comprising 4·16 million people, we estimate that new-onset AA peaks at age 25–29 years. People of Asian ethnicity, and from socially deprived and urban areas, are more likely to present with AA. After diagnosis, one in four people with AA are referred for specialist dermatology review. Specialist referral rates are lower in people from more socially deprived areas.