Background: Several studies have provided evidence of a strong association between asthma and allergic or nonallergic rhinitis, leading to the hypothesis that allergic rhinitis (AR) and asthma represent a continuum of the same disease.
The aims of our study were: (i) to measure the comorbidity of AR and asthma and asthma-like symptoms and (ii) to assess whether asthma, AR, and their coexistence share a common pattern of individual risk factors.
Methods: The subjects are participants from the Italian multicentre, cross-sectional survey on respiratory symptoms in the young adult general population (Italian Study of Asthma in Young Adults, ISAYA). The relationship between individual risk factors and asthma, AR and their coexistence, was studied by means of a multinomial logistic regression.
Results: About 60% of asthmatics reported AR. On the other hand, subjects with AR presented an eightfold risk of having asthma compared to subjects without AR. Age was negatively associated with asthma [OR = 0.89, 95% confidence interval (CI): 0.82-0.96], AR (OR = 0.92, 95% CI: 0.86-0.98), and asthma associated with AR (OR = 0.83, 95% CI: 0.79-0.88). The risk of AR without asthma was significantly higher in the upper social classes (OR = 1.23, 95% CI: 1.08-1.39). Active current smoking exposure was positively associated with asthma alone (OR = 1.24, 95% CI: 1.09-1.41) and negatively associated with AR with (OR = 0.69, 95% CI: 0.54-0.88) or without (OR = 0.76, 95% CI: 0.69-0.84) asthma.
Conclusions: Asthma and AR coexist in a substantial percentage of patients; bronchial asthma and AR, when associated, seem to share the same risk factors as AR alone while asthma without AR seems to be a different condition, at least with respect to some relevant risk factors.