Sleep-disordered Breathing in Patients with COPD: Prevalence and Outcomes

The prevalence of obstructive sleep apnea (OSA) or nocturnal hypoxemia without OSA (isolated nocturnal hypoxemia -iNH-) and its impact on the natural history of COPD are unclear. We determined the prevalence of OSA and iNH in patients with COPD, and their contribution to all-cause mortality and COPD exacerbations. We performed home sleep apnea testing in the COPD History Assessment in SpaiN (CHAIN) study cohort at baseline. Prevalent OSA was defined by an apnea-hypopnea index -(AHI- 15/h) and iNH was defined by a SpO2 < 90% for >30% of the nocturnal recording time. We evaluated the association of comorbid OSA or iNH with all-cause mortality using multivariate multivariable Cox regression models and with COPD exacerbations using negative binomial models. Among 428 COPD patients, OSA and nocturnal hypoxemia were ruled out in 41%, while 27% had iNH and 32% had OSA (overlap syndrome COPD/OSA -OVS-). OVS was independently associated with obesity as defined by a BMI ≥ 30 kg/m2, and with severe COPD exacerbations (p<0.01), whereas iNH was associated with lower FEV1 and lower resting SaO2. Compared to COPD patients without OSA or iNH, those with untreated OVS had a greater mortality (HR: 1.74 95% CI=1.03-2.94) and risk of COPD exacerbations (IRR: 1.44, 95% CI,1.05-2.03). OSA and iNH are frequent in patients with COPD and the prevalences decrease or increase respectively with the disease severity. COPD patients with untreated OVS but not with iNH had a greater risk of all-cause mortality and COPD exacerbations.