Age-related prevalence of allergic diseases in Tokyo schoolchildren

Background: The International Study of Asthma and Allergies in Childhood (ISAAC) has reported the prevalence of asthma and allergic diseases in many countries. Methods: We used the ISAAC core written questionnaire to examine the prevalence of asthma and allergic diseases in 6- to 14-year old schoolchildren in Tokyo. In 2005, we conducted a cross-sectional survey of all schoolchildren in all public schools located in the Setagaya area of Tokyo. Results: Data were collected from 27,196 children in 95 schools. Prevalence ranged from 10.5% to 18.2% for asthma symptoms and from 10.9% to 19.6% for atopic dermatitis, with both conditions tending to decrease with age. As has been previously reported for all age groups, significantly higher rates of current asthma are observed in boys than in girls. The prevalence of allergic rhinoconjunctivitis exhibited a different pattern from that of asthma and atopic dermatitis, peaking at the age of 10 (34.8%). Prevalence of allergic rhinoconjunctivitis was 1.5 to 2-fold higher than the previous ISAAC studies that were performed in Tochigi and Fukuoka. In all age groups, symptoms of allergic conjunctivitis were more frequent from February to May, which coincides with the Japanese cedar pollen season, and were less frequent between June to September. Conclusions: The prevalence of asthma and atopic dermatitis was higher in younger schoolchildren. Tokyo schoolchildren appear to have extremely high prevalence rates of seasonal allergic rhinoconjunctivitis.