Prevalence and determinants of co-morbidities in patients with obstructive apnea and chronic obstructive pulmonary disease

The co-existence of obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD) in a single patient has been described as the “overlap syndrome” (OS). Although OSA determines a significant cardiovascular risk, little is known on the burden of morbidities in patients with overlap. Methods: We compared the prevalence of co-morbidities and assessed factors determining multi-morbidity in patients with OSA or OS, by retrospectively analyzing clinical records of 866 patients (295 OSA, 219 OS and 352 simple snorers) referred to our Sleep Laboratory. Results: Although a comparable apnea/hypopnea index, patients with OS had a lower diurnal and mean nocturnal oxygen saturation (SaO2%) and spent more time with SaO2 <90%. Hypertension, cardiovascular diseases, diabetes mellitus, and gastro-esophageal reflux were common in both OSA and OS patients. Hypertension was the most common disease in all groups with a higher prevalence in OS (54.3 %) than in OSA (45%) and controls (17%), followed by cardiovascular diseases found in 35.6% of OS patients, 17.5% of OSA and 8.8% of controls. In a model of multivariate logistic regression analysis, the patients’ age and the presence of COPD were the only independent factors predicting the risk of hypertension and cardiovascular diseases. The risk of multi-morbidity (3 co-morbidities) was also predicted by the age and by the presence of COPD (6-fold increase). Conclusions: The burden of chronic conditions is significantly higher in the overlap syndrome than in simple OSA. This is due to the fact that COPD per se increases the risk of morbidities and to the older age of the patients.