Indoor and outdoor environmental exposures, parental atopy, and physician-diagnosed asthma in Taiwanese schoolchildren.

OBJECTIVE Parental atopy and environmental exposures are recognized risk factors for childhood asthma. However, the relative contributions of specific risk factors and the overall contributions of indoor and outdoor exposures remain unexplored. This study was undertaken to identify risk factors, estimate the population attributable risk of each exposure, and compare the data for boys versus girls for physician-diagnosed asthma in Taiwanese schoolchildren. METHODS During a February to June 2001 cross-sectional national survey, 35 036 6- to 15-year-old schoolchildren were chosen from 22 elementary and 22 middle schools located within 1-km catchment areas of 22 air-monitoring stations in Taiwan. The main outcome measure was physician-diagnosed asthma, as reported by the parents. We investigated hereditary and indoor and outdoor environmental factors for childhood asthma by questionnaire. The adjusted prevalences of questionnaire-determined outdoor indicators were also compared with air-monitoring data. RESULTS Outdoor air pollutants were associated with parent-reported perceived ambient air pollution. Physician-diagnosed asthma was reported for 8.1% of the boys (1330 of 16 441) and 5.6% of the girls (894 of 16 056). The risk of physician-diagnosed asthma was significantly associated with parental atopy and perceived ambient air pollution in both sexes. The presence of visible cockroaches (odds ratio [OR]: 1.30; 95% confidence interval [CI]: 1.07-1.59), mold on walls at home (OR: 1.20; 95% CI: 1.01-1.41), and water damage (OR: 1.33; 95% CI: 1.02-1.70) were also associated with asthma in girls; however, only visible mold on walls at home was related to asthma in boys. Mutually adjusted analytical models produced statistically significant associations between any indoor factor and asthma in girls (OR: 1.24; 95% CI: 1.00-1.56) but not in boys (OR: 1.04; 95% CI: 0.87-1.25). For all hereditary and environmental factors, the total population attributable risk was 44.31% in boys and 60.61% in girls. CONCLUSIONS Parental atopy contributed more to childhood asthma than indoor or outdoor environmental factors. Girls may be more susceptible to indoor factors than boys.