Prevalence of physician-diagnosed asthma in patients with suspected obstructive sleep apnea syndrome: a cross-sectional analysis of the ESADA database

It has been reported that bronchial asthma is often associated with obstructive sleep apnea (OSA) and daytime sleepiness. We analyzed the prevalence of physician-diagnosed asthma in 4929 subjects with suspected obstructive sleep apnea (OSA) in the European Sleep Apnea database (ESADA) Cohort. Patients were studied by respiratory polygraphy (PG: n=1624, 66.6% males) or full polysomnography (PSG: n=3305, 70.4% males), and the clinical characteristics of asthmatic (A) and non-asthmatic (non-A) patients were analyzed according to OSA severity. Significance was at p<0.05. Prevalence of physician-diagnosed asthma was 6.8% (n=111) in the PG group, and 7.0% (n=231) in the PSG group, with a higher frequency in females (F: 10.2%, M: 5.3%, p<0.0001). Compared to non-A patients, A patients were slighly heavier (mean BMI±SD: 32.8±7.6 vs 31.2±7.8 kg/m2, p=0.0004) and showed more severe daytime sleepiness (Epworth score: 10.4±5.6 vs 9.5±5.3, p=0.0015) and a trend for worse nocturnal lowest SaO2 (p=0.053). Asthmatic patients showed normal AHI (<5, n=1009) more often than non-A patients (9.0 vs 6.4%, p=0.003). As for sleep structure in PSG group, SWS was significantly less represented in A than non-A patients (21.9±15.5 vs 25.8±17.2%, p=0.0009). In conclusion, among patients undergoing sleep studies for suspected OSA, prevalence of physician-diagnosed asthma was not high. In asthmatic patients, sleep was disturbed even in the absence of OSA, suggesting a referral bias of asthmatic patients to the sleep clinic, possibly due to nocturnal symptoms of asthma.