Increasing prevalence of allergic rhinitis symptoms in an adult Danish population

There is evidence that the prevalence of respiratory allergy is increasing. This is mainly based on studies in children and young adults. The aim of the study was to compare the prevalences of self-reported symptoms of respiratory allergy among Danish adults in two surveys 8 years apart. Identical questionnaires were mailed to two random general population samples in 1989 and 1997. The response rates were 86.1% (n=3603) and 86.4% (n=817), respectively. The sampling frame and sampling method were identical in both surveys. The changes in the prevalences of symptoms were expressed by sex- and age-adjusted odds ratios comparing 1997 to 1989. We found a significant increase in the prevalence of seasonal rhinitis symptoms (OR=1.6, 95% CI 1.4-1.9), rhinitis symptoms on exposure to pollen (OR=1.6, 95% CI 1.4-1.9), rhinitis symptoms on exposure to furry animals (odds ratio 1.6, 95% CI 1.3-2.0), rhinitis symptoms on exposure to house dust (OR=1.3, 95% CI 1.1-1.6), and breathlessness on exposure to pollen (OR=1.5, 95% CI 1.0-2.0). The observed increases were independent of sex and age. The questionnaire was validated in relation to allergen skin test reactivity in a subgroup of the responders to the 1989 survey. When the estimated associations between symptoms and skin test reactivity were considered, the results suggested an increase in allergy to pollen and animal dander. In conclusion, we found evidence of increased prevalence of allergic rhinitis symptoms associated with skin test reactivity.