Is asthma prevalence still increasing?

Increased awareness of asthma in society and altered diagnostic practices makes evaluation of data on prevalence change difficult. In most parts of the world the asthma prevalence seems to still be increasing. The increase is associated with urbanization and has been documented particularly among children and teenagers in urban areas of middle- and low-level income countries. Use of validated questionnaires has enabled comparisons of studies. Among adults there are few studies based on representative samples of the general population which allow evaluation of time trends of prevalence. This review focuses mainly on studies of asthma prevalence and symptoms among adults. Parallel with increased urbanization, we can assume that the increase in asthma prevalence in most areas of the world will continue. However, in Australia and North-West Europe studies performed, particularly among children and adolescents, indicate that the increase in asthma prevalence may now be leveling off.