Investigation of association between indoor environmental factors and child health problems in Japan - Design of survey and outcome from preliminary cross-sectional questionnaire

In Japan, there is an increase in allergic diseases such as asthma, respiratory symptom, particularly prevailing among the young generation. The reasons why the prevalence is increasing are still not yet well understood. However, it is deemed that indoor environmental factors are one of the essential sources. Therefore, an epidemiology type of survey was investigated on the 4th and 5th grade school children in Japan. The survey was divided into three phases. Phase 1 was a preliminary cross-sectional questionnaire of the prevalence of health problems. Phase 2 was a cross-sectional questionnaire survey on housing characteristics and health. Phase 3 was a field measurement for case control. This paper describes the study protocol and the outcomes from Phase 1. The prevalence of current allergic symptoms was 49.9%. Asthma and rhinitis of the children were 12.5% and 33.3%, respectively. The prevalence of several allergic symptoms among boys was significantly higher than in girls. It indicated that the environmental factors such as pollen, indoor house dust and dust mites could influence allergic symptoms. This survey reveals the ratio of children allergic symptoms in Japan and the possibility of the association between adverse health effect and indoor environmental factors.