Background: To identify risk factors for childhood wheezing and allergies, a questionnaire regarding family histories and environmental factors was added to the International Study of Asthma and Allergies in Childhood (ISAAC) Phase One questionnaire and the associations between current prevalence and risk factors were analyzed.
Methods: Questionnaires were completed by 4466 schoolchildren, who were 13–14 years of age, in Tochigi Prefecture. Children were divided into groups on the basis of risk factors and the severity of each allergic disease according to answers to the ISAAC questionnaire.
Results: In analyses of family histories, the odds ratios (OR) of children who have a family history with no symptoms were significantly lower by risk factor-based analyses compared with those children with a family history of symptoms of wheezing (OR = 2.34–4.39), rhinitis (1.76–2.68) and eczema (2.54–7.81), and significant correlations were observed between severity and family history in all diseases by the Mantel test (P < 0.001). Although the OR of household smoking was not significant, heavier smoking in a household had an effect on severity and showed a significant correlation with severity in rhinitis (P < 0.05) and eczema (P < 0.01). Regarding road traffic, the percentage of children living in an area with heavy traffic showed a significant correlation with the severity of wheezing (P < 0.05) and no children with severe wheezing lived in areas with light traffic. In addition, the mean percentage of children with current wheezing between school locations was significantly higher in the city area (10.2 ± 0.7%) compared with that in the suburbs (6.6 ± 0.9%; P = 0.01) and industrial areas (6.6 ± 0.7%; P = 0.01).
Conclusions: These results suggest that the family histories may have potential effects on the severity of allergic diseases and that household smoking for rhinitis and eczema and heavy road traffic for asthma may be more important modifiable risk factors for severity in Japan.