Increase in the self‐reported prevalence of asthma and hay fever in adults over the last generation: a matched parent–offspring study

Abstract

The study compared current measures on a population-based cohort of adults with past measures on their parents to determine whether the prevalence of self-reported asthma and hay fever in adults increased between 1968 and the early 1990s. In 1968, 8585 cohort members (99 per cent of eligible Tasmanian 7-year-old school children born in 1961), 16 273 (95 per cent) of their parents (mean age 35 years) and 20 937 siblings completed a questionnaire about asthma and hay fever. In 1991–1993, 1494 members (75 per cent) of a stratified random sample of the cohort (aged 29 to 32 years), 75 per cent resident in Tasmania, were surveyed again. In 1968, the proportion of parents who reported having ever had asthma or attacks of wheezing like asthma was 10.9 per cent, independent of age and sex. In 1991–1993, the estimated adult prevalence of having ever suffered from attacks of asthma or wheezy breathing was 23.2 per cent. The proportion reporting at least one asthma attack within the previous 10 years, 5 years, 2 years, 12 months and 6 months was 17.6 per cent, 16.1 per cent, 14.5 per cent, 13.3 per cent and 10.3 per cent, respectively. For hay fever, the adult prevalence was 19.2 per cent in 1968, and 41.3 per cent in 1991–1993. The self-reported lifetime prevalence of asthma and hay fever among adults in the 1961 birth cohort of Tasmanians was twice as high in 1991–1993 as in their parents 25 years earlier. The change in disease interpretation necessary to account fully for the change in prevalence provides evidence for a real increase. Nevertheless, unavoidable subtle differences in questioning could account for half the observed change in prevalence.