Is physician-diagnosed allergic rhinitis a risk factor for the development of asthma?

There is strong evidence that there is a relationship between allergic rhinitis (AR) and asthma, but it is unclear whether there is a causal relation between AR and asthma. The aim of this study was to assess prospectively whether AR is a risk factor for the diagnosis of asthma in a large primary care population.

We performed a historic cohort study of life-time morbidity that had been recorded prospectively since 1967 in four general practices. Two groups of subjects were selected: (i) patients with diagnosis of AR, (ii) a control group matched using propensity scores. We assessed the risk of physician-diagnosed asthma in patients with physician-diagnosed AR compared to subjects without a diagnosis of AR (controls).

The study population consisted of 6491 subjects (n = 2081 patients with AR). Average study follow-up was 8.4 years. In patients with AR, the frequency of newly diagnosed asthma was 7.6% (n = 158) compared to 1.6% (n = 70) in controls (P < 0.001). After adjusting the effect of AR on asthma diagnosis for registration time, age, gender, eczema and socioeconomic status, having AR was a statistically significant risk factor for asthma (hazard ratio: 4.86, P < 0.001, 95% confidence interval: 3.50-6.73, controls as reference).

A diagnosis of AR was an independent risk factor for asthma in our primary care study population. Having physician-diagnosed AR increased the risk almost fivefold for a future asthma diagnosis.