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Abstract
BACKGROUND It is the general impression that the prevalence of asthma has increased during recent decades. A study was undertaken to investigate asthma prevalence, respiratory symptoms, and lung function in young adults in the City of Copenhagen 15 years apart.
METHODS Men and women aged 20–35 years were sampled from the general population living in a defined area of central Copenhagen. The first examination took place in 1976–8 and comprised 1034 subjects (response rate 67.2%). A new sample comprising 1104 subjects (response rate 62.6%) from exactly the same area was examined 15 years later in 1991–4. All participants answered a questionnaire on respiratory symptoms and diseases and performed spirometric tests with measurement of forced expiratory volume in one second (FEV1) and forced vital capacity (FVC).
RESULTS The prevalence of self-reported asthma increased from 1.5% in the first survey to 4.8% in the second survey (p<0.001). Asthmatic subjects had, on average, poorer lung function than non-asthmatic subjects in terms of FEV1 and this difference was more pronounced in the second survey than in the first (10.0% of predicted versus 2.4% of predicted). Smoking decreased significantly from 62% in 1976–8 to 45% in 1991–4 (p<0.001).
CONCLUSIONS The prevalence of self-reported asthma has increased significantly among young adults in Copenhagen over a 15 year period. The severity of asthma, as judged by the level of FEV1, has also increased. These findings cannot be explained by changes in smoking habits.
- asthma prevalence
- asthma severity
- smoking
- epidemiology