Although climate conditions have been reported to be related with childhood eczema, the relationship between ultraviolet (UV) and eczema is not fully understood. Our aim was to assess the association between UV index and the prevalence of childhood eczema.
Data from the 2008 nationwide, cross-sectional, questionnaire-based survey in Japan was analyzed. In this survey, children in three age groups (6–7-year-old, 13–14-year-old and 16–17-year-old) were selected from a random sample of schools from all 47 prefectures. UV index of each prefecture was acquired from the data of the Japan Meteorological Agency, and was categorized into quartiles.
Of the179, 218 children recruited, 149,464 replied to the questionnaire. After omitting incomplete data, 138,128 were analyzed. Even after adjusted for confounders including climate factors, the prevalence of current eczema in 6–7-year-old boys in prefectures with the third- and highest-quartile mean annual UV index were significantly lower compared to that with the lowest-quartile (p=0.01 and p<0.001). In adolescents, the prevalence of current eczema in the highest-quartile was significantly lower compared to those with the lowest-quartile for boys (p=0.001 in 13–14-years-old boys and p=0.02 in 16–17-years-old boys). However, there was no significant association between mean annual UV index and the prevalence of current eczema for girls in all three age-groups.
UV index was significantly associated with the prevalence of current eczema in boys, but not in girls. This study was supported by the Health and Labour Sciences Research Grant for Research on Allergic Disease and Immunology from the Ministry of Health, Labour and Welfare, Japan.