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Increasing prevalence of alopecia areata in South Korea

Dear Editor, Alopecia areata (AA) is a common inflammatory condition affecting hair. The severity of AA ranges from patchy AA over the scalp, to alopecia totalis (AT), resulting in complete loss of scalp hair, and to alopecia universalis (AU), leading to complete loss of all hair. Although AA is common, epidemiological studies of AA are still scarce, especially in Asia. Therefore, we analyzed a nationwide representative sample cohort of over 1 million South Koreans using data from the National Health Insurance Service – National Sample Cohort to investigate the prevalence and incidence of AA, including AT and AU. Statistical analyses were performed using SAS Enterprise Guide 7.1 (SAS Institute, Cary, NC, USA). The 8-year overall incidence between 2006 and 2013 was 98.5 (95% confidence interval [CI], 96.6–104.4) per 100 000 person-years. Poisson regression analysis revealed a 1.02-fold annual increase in incidence rate during this period (P = 0.001). The average prevalence of AA was 154.6 (95% CI, 134.9–174.3) per 100 000 persons, with a steady increase reaching 1.5-fold over the 8 years (Fig. 1a). The mean prevalence of AT and AU per 100 000 persons was 3.7 (95% CI, 3.5–3.9) and 0.9 (95% CI, 0.7–1.1), respectively (Fig. 1b). The mean prevalence of AT and AU per 100 AA patients was 2.4 (95% CI, 2.2–2.7) and 0.6 (95% CI, 0.5–0.7), respectively. Three out of 100 AA patients were either AT or AU patients. The increase in incidence and prevalence of AA may coincide with the increase in the concurrent autoimmune disorders, such as autoimmune thyroid disease. A US study has also reported an increase in incidence that at 2.1%, the cumulative lifetime incidence of AA from a recent 20-year period (1990– 2009), was slightly higher than the 1.7% observed in the previous 20-year period (1975–1989). It also mentions the rise in