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.