The link between allergic rhinitis and allergic asthma: A prospective population-based study. The Copenhagen Allergy Study

Background: It has been hypothesized that allergic rhinitis and allergic asthma are manifestations of the same disease entity. We aimed to investigate the relationship between allergic rhinitis and allergic asthma. Methods: Participants in a population-based study of 15-69-year-olds in 1990 were invited to a follow-up in 1998. A total of 734 subjects were examined on two occasions eight years apart. Allergic rhinitis to pollen was defined as a history of nasal symptoms on exposure to pollens and IgE specific to pollen. Allergic asthma to pollen was defined as a history of lower airway symptoms on exposure to pollens and IgE specific to pollen. Similarly, diagnoses of allergic rhinitis and allergic asthma to animals or mite were defined. Results: At follow-up, all subjects with allergic asthma to pollen (n = 52) had in addition allergic rhinitis to pollen. In the longitudinal analysis, there were a total of 28 new (incident) cases of allergic asthma to pollen. They all had allergic rhinitis to pollen at baseline, or had developed allergic rhinitis to pollen at follow-up. Accordingly, allergic rhinitis to animals and mite were ubiquitous in subjects with allergic asthma to animals and mite, respectively. Conclusions: The results support the hypothesis that allergic rhinitis and allergic asthma are manifestations of the same disease entity.