Current asthma, respiratory symptoms and airway infections among students in relation to the school and home environment in Japan.

Objective: To study associations between the school and home environment and current asthma, respiratory symptoms and airway infections among Japanese students. Methods: Japanese students (12-15 y) (N = 1048) in four schools responded to a questionnaire on respiratory health, allergy and the home environment. Temperature, relative air humidity (RH) and student density (students/m(2) floor area) was measured in the classrooms: dust was collected from floors and in classroom air and analysed for cat (Fel d 1) and dog (Can f 1) allergens. Health associations were analysed by multi-level logistic regression. Results: Doctor's diagnosed asthma was common (13.4%), 8.8% reported cat allergy and 6.1% dog allergy. The median level in floor dust was 41ng/g (IQR 23-92) for Fel d 1 and 101ng/g (IQR 54-101) for Can f 1. The median level in air was 18.6ng/ m(2)/ day (IQR5.9-25.1) for Fel d 1 and 18.6ng/ m(2)/ day (IQR 6.0-13.3) for Can f 1. High RH, high student density and airborne cat allergen was associated with airway infections. In the home environment, recent indoor painting, new floor materials, odour, having cats as pets, window pane condensation in winter, and dampness in floor construction were associated with respiratory illness. Conclusion: High relative air humidity, high student density and airborne cat allergens at school may increase the risk of airway infections. Having cats as pets, chemical emissions from paint and new floor materials, odour and dampness can constitute domestic risk factors for respiratory symptoms while having dogs as pets could be protective.