Long-term changes in adult asthma prevalence

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Abstract
There has been an increase in asthma prevalence among children. Little evidence is available regarding long-term changes in asthma prevalence in adults.Two cross-sectional studies were performed among adults aged 15–70 yrs in Oslo, Norway, in 1972 and again in 1998–1999 (n=39,998). A postal self-completed questionnaire was used. Exactly the same questions and survey methods were used in both studies. In 1998–1999, additional telephone follow-up was included for postal nonresponders.The crude prevalence of ever having had a doctor's diagnosis of asthma increased from 3.4 to 9.3%. The prevalence of wheezing increased from 17.8 to 25.8% and attacks of breathlessness from 12.6 to 16.7%. After controlling for smoking, the risk of asthma among those aged <40 yrs had tripled. The increase in asthma was 50% greater in females than males. The prevalence of symptoms increased less than asthma diagnosis. Wheezing increased by 50% in those aged 40 yrs.