Impact of pollution and place of residence on atopic diseases among schoolchildren in Telemark County, Norway.

For estimation of the prevalence, degree of severity, and association with outdoor pollution, a questionnaire on asthma and other atopic diseases was distributed to the parents of 4666 7-13-year-olds, comprising all the children in 36 schools in Telemark County, Norway, including 37% of the schoolchildren in the county. The response rate was 94%. In a validity study employing clinical evaluations, the questionnaire-based diagnosis of asthma was found to have a sensitivity of 0.96 and a specificity of 0.88. The lifetime prevalence of asthma in Telemark was 9% (boys 11.3%, girls 6.6%; p < 0.001). There was no significant difference in the lifetime prevalence of asthma by pollution zone; 8.3% in heavily, 9.3% in moderately, and 9.2% in minimally polluted zones. The asthma prevalence was significantly higher (14.2%; p < 0.05) among boys in the coastal area of the county than in the mountainous area (8.9%). Both of these areas were in the minimal pollution zone. Of asthma cases, 67% were categorized as mild, 29% as moderate, and 4% as severe. The lifetime prevalence was 17.8% (boys 21.3%, girls 14.2%; p < 0.001) for allergic rhinitis, 13.2% (boys 11.4%, girls 15.2%; p < 0.001) for atopic eczema, and 29.6% (boys 31.7%, girls 27.4%; p < 0.01) for overall atopic disease (asthma, allergic rhinitis, eczema). These findings are not compatible with the hypothesis that outdoor pollution is associated with the lifetime prevalence of asthma in school-age children. The results also show that less than 0.5% of schoolchildren suffer from severe asthma.