Regional Differences in the Prevalence of Atopic Dermatitis among Schoolchildren in Japan and Its Associated Factors from 2006 to 2018

The trends in the prevalence of atopic dermatitis for each prefecture over recent years have not been investigated in Japan, and no studies investigating the factors associated with the prevalence using nationwide data have been conducted. We investigated the trends in the prevalence of atopic dermatitis among schoolchildren for each prefecture in Japan from 2006 to 2018 and identified the factors associated with regional differences in prevalence. The data on the atopic dermatitis prevalence in schoolchildren aged 6–17 years were collected as part of the School Health Statistics Research. The demographic, socioeconomic, medical, and environmental characteristics of the prefectures were examined for possible associations with the prevalence. The age-standardized prevalence rates of atopic dermatitis were calculated separately for boys and girls and by prefecture and year. We examined the associations between the age-standardized prevalence rates and prefectural characteristics using an ecological study. The age-standardized prevalence rates of atopic dermatitis tended to be stable for Japan as a whole, whereas the trend in the age-standardized prevalence rates differed across prefectures. In the regression analysis, the year was negatively associated and the number of medical clinics per 100,000 persons was positively associated with the age-standardized prevalence in girls. The taxable income per capita was positively associated with the age-standardized prevalence both in boys and in girls.