Greater risk of incident asthma cases in adults with allergic rhinitis and effect of allergen immunotherapy: a retrospective cohort study

Abstract

Asthma and rhinitis are often co-morbid conditions. As rhinitis often precedes asthma it is possible that effective treatment of allergic rhinitis may reduce asthma progression. The aim of our study is to investigate history of allergic rhinitis as a risk factor for asthma and the potential effect of allergen immunotherapy in attenuating the incidence of asthma. Hospital-referred non-asthmatic adults, aged 18-40 years between 1990 and 1991, were retrospectively followed up until January and April 2000. At the end of follow up, available subjects were clinically examined for asthma diagnosis and history of allergen specific immunotherapy, second-hand smoking and the presence of pets in the household. A total of 436 non-asthmatic adults (332 subjects with allergic rhinitis and 104 with no allergic rhinitis nor history of atopy) were available for final analyses. The highest OR (odds ratio) associated with a diagnosis of asthma at the end of follow-up was for the diagnosis of allergic rhinitis at baseline (OR, 7.8; 95%CI, 3.1-20.0 in the model containing the covariates of rhinitis diagnosis, sex, second-hand smoke exposure, presence of pets at home, family history of allergic disorders, sensitization to Parietaria judaica; grass pollen; house dust mites; Olea europea: orchard; perennial rye; and cat allergens). Female sex, sensitization to Parietaria judaica and the presence of pets in the home were also significantly predictive of new onset asthma in the same model. Treatment with allergen immunotherapy was significantly and inversely related to the development of new onset asthma (OR, 0.53; 95%CI, 0.32-0.86). In the present study we found that allergic rhinitis is an important independent risk factor for asthma. Moreover, treatment with allergen immunotherapy lowers the risk of the development of new asthma cases in adults with allergic rhinitis.

Figure 1

Study flow diagram. Medical records of cases who were referred in the period between January 1990 and December 1991 to the clinic for the diagnosis and treatment of allergic diseases were reviewed. To be included in the study cases had to be between the ages of 18 and 40 years and not diagnosed with asthma at the time of referral. A total of 1104 records were selected at baseline. In the period from January to April 2000, subjects were contacted for a follow up visit to evaluate the possibility of asthma diagnosis; 629 subjects were lost to follow-up leaving 475 subjects taking part in the study. A diagnosis of asthma could not be established with confidence in 39 subjects, leaving a total of 436 subjects for the final analyses. Among those 436 subjects, 332 had allergic rhinitis and 104 had no allergic rhinitis or history of atopy. At follow up, 46.1% (n = 153) of those with rhinitis at baseline developed asthma.

Figure 2

Diagnostic procedures. With the exception of skin prick testing – SPT, case history (paying particular attention to the presence of a past or present history of asthma and/or previous asthma symptoms or asthma medication intake), physical examination and simple spirometry were repeated at baseline (1990–91) and follow-up visits (2000). Bronchial provocation testing – BPT with inhaled methacholine were carried out in selected cases on both visits.

Figure 3

Percentage of new onset asthma by the end of the study in allergen immunotherapy (SIT) treated (closed bar) and untreated (open bar) subjects with allergic rhinitis.

Figure 4

Percentage of new onset asthma by the end of the study in Parietaria immunotherapy (SIT) treated (clear pointed bar) and untreated (dark pointed bar) allergic rhinitic subjects with positive skin prick test to Parietaria.

Figure 5

Percentage of new onset asthma by the end of the study in HDM immunotherapy (SIT) treated (clear hatched bar) and untreated (dark hatched bar) allergic rhinitic subjects with positive skin prick test to HDM.