Nocturnal symptoms perceived as asthma are associated with obstructive sleep apnoea risk, but not bronchial hyper-reactivity.

ABSTRACT

BACKGROUND AND OBJECTIVE: Obstructive sleep apnoea (OSA) and asthma are associated, and nocturnal breathing difficulty that is usually identified as asthma-like symptoms can be present in both conditions. We investigated how nocturnal asthma-like symptoms (NAS) and bronchial hyper-reactivity (BHR) contribute to the association between OSA risk and current asthma, which is currently unknown but a clinically important question. METHODS: We used data from 794 middle-aged participants in a population-based cohort who provided information on OSA risk (defined by a STOP-Bang questionnaire score of at least 3), current asthma and NAS, and underwent methacholine bronchial challenge testing. Using regression models, we examined the association between OSA risk and current asthma-NAS subgroups and investigated any effect modification by BHR. RESULTS: The participants were aged 50 years (49.8% male). OSA risk was associated with NAS with or without current asthma (odds ratio (OR) 2.6; 95% CI = 1.3-5.0; OR 4.2; 95% CI = 1.1-16.1, respectively), but not with current asthma in the absence of NAS. BHR was associated with current asthma with or without NAS (OR 2.9; 95% CI = 1.4-5.9; OR 3.4; 95% CI = 2.0-7.0, respectively) but not with NAS in the absence of current asthma. The associations between OSA risk and current asthma were neither modified nor mediated by BHR. CONCLUSION: Our findings suggest that some of the nocturnal symptoms perceived as asthma may be OSA symptoms. Patients with nocturnal asthma symptoms should be considered for possible OSA.