Increase of asthma, allergic rhinitis and eczema in Swedish schoolchildren between 1979 and 1991

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Abstract
Background: A previous study has shown a twofold increase in prevalence of asthma and allergic rhinitis (AR) in Swedish recruits during the 1970s. The increase was higher in more northerly colder regions. Objectives To follow up the previously found trend to increasing prevalences with time as well as the climatic variations within the country. Methods: The prevalences of asthma, allergic rhinitis and eczema were assessed using two questionnaire studies, 12 years apart (1979 and 1991) with identical questions about the diseases. The study comprised representative samples of children from the Göteborg area on the south-western coast (in 1979: 7-year-olds, n= 4255, in 1991: 7-year-olds, n= 1649) and in Kiruna, a mining town in the northernmost inland mountains (in 1979: 7-year-olds, n= 427, in 1991: 7-9-year-olds, n= 832). In 1991 there was also a personal interview and a skin-prick test (SPT) on subsamples. Results: The prevalence of all these diseases present over the last year had roughly doubled over the 12-year period. On both occasions, most symptoms were more prevalent in the northern area. In 1991, the prevalence of one or more symptoms in Goteborg was 23.8% and 32.5% and in Kiruna 29.9% and 44.8% in the questionnaire and the interview, respectively. Conclusion: Asthma, AR and eczema increase continuously in prevalence in Sweden and the climatic distribution of the prevalences suggests possible major risk factors to be found in a closed indoor climate.