Cross-sectional study of allergic disorders in relation to familial factors in Japanese adolescents

AIM: The roles of heredity and the household environment in the development of allergic disorders are not clearly established. This study examined the relationship between selected familial factors and the prevalence of symptoms of wheeze, atopic eczema and rhinoconjunctivitis in Japanese adolescents. METHODS: Study subjects were 5539 students aged 12-15 y in Suita City. A questionnaire ascertained gender, grade, number of older siblings, maternal age at childbirth, smoking in the household, domestic pets and parental history of allergy, as well as signs and symptoms of allergy in the previous 12 mo. The latter were based on diagnostic criteria from the International Study of Asthma and Allergies in Childhood. RESULTS: Male gender was independently associated with an increased prevalence of wheeze and a decreased prevalence of atopic eczema. The prevalence of rhinoconjunctivitis, but not wheeze or atopic dermatitis, significantly increased with advancing grade. A significant inverse dose-response relationship between the number of older siblings and the prevalence of rhinoconjunctivitis, but not wheeze or atopic dermatitis, was observed. Maternal age at childbirth, smoking in the household and domestic pets were not apparently related to any of the allergic disorders. A positive maternal allergic history was more evidently associated with an increased prevalence of wheeze and rhinoconjunctivitis, but not atopic eczema, than a positive paternal allergic history. CONCLUSION: The findings suggest that the factors associated with allergic disorders in Japan are largely the same as those already identified in Western populations.