Prevalence of alopecia areata in Japan: Estimates from a nationally representative sample.

Data on the prevalence of alopecia areata (AA) in Japan is limited and the epidemiology of the disease there is not well understood; therefore, it is critical to examine the prevalence and severity of AA in Japan to inform the need for future treatments and research. A cross-sectional, web-based survey was conducted in Japan from January through March 2021. A total of 45 006 participants were identified through general population survey panels and asked about their experience with AA and hair loss. The Alopecia Assessment Tool and the Scalp Hair Assessment PROTM were adopted to screen for history of AA and assess disease severity, respectively. Eligible participants submitted photos of their scalp, which were reviewed by three board-certified dermatologists to evaluate the presence and severity of AA. Prevalence and severity estimates were calculated using participants' self-reported data and verified through the dermatologists' assessments. The participant-reported point prevalence of AA was 2.18%. The adjusted point prevalence following physician adjudication using participant-submitted photos was 1.45%. Topical corticosteroids were the most commonly used treatments, with 34.6% of participants diagnosed with AA reported having ever used them. Participants also reported negative impacts on their mood (70.2%), self-esteem (55.8%), and social interactions (48.9%). Despite the social and emotional impact of hair loss, more than one third of those reporting a physician diagnosis of AA were not currently seeking treatment. The current study identified an estimated prevalence of AA in Japan between 1.45% and 2.18% based on the survey results and physician-adjudication of those findings. Considering the impactful psychological burden of AA, the survey results showing that 38.90% of surveyed patients do not currently seek treatment may indicate an unmet need for remedies.