Prevalence and characteristics of patients with obstructive sleep apnea (OSA) and Chronic Obstructive Pulmonary Disease (COPD): “Overlap Syndrome”

<bold>Background:</bold> OVS is a distinct clinical entity, that seems to result in potential CV consequences. <bold>Aim:</bold> To estimate the prevalence and risk factors for OVS in a large cohort of OSA patients and to analyze clinical and PSG characteristics associated with this syndrome. <bold>Methods:</bold> In this cross-sectional study, 2,563 consecutive patients evaluated for OSA underwent type 1 PSG. They were grouped as pure OSA patients (AHI>15/hr), and patients with OVS. Demographic, PSG data, PFTs and ABGs were measured and compared between groups, after adjustments for confounders. <bold>Results:</bold> OSA was diagnosed in 2,069 out of 2,563 patients (81%). Of those 427 (21%) had OVS. These patients were significantly older (65 vs 55) more obese (BMI 37 vs 35), with increased neck circumference (45 vs 43) and predominantly current or former smokers (92 vs 62%,p<0.001). Comorbid Hypertension (67 vs 48%), DM (30 vs 19%) and CV disease (37 vs 19%) were more prevalent in OVS compared to OSA. OVS patients had also lower PaO2 (71 vs. 81), higher PaCO2 (44 vs 39) and HCO3 (27 vs 25). Indices of OSA severity were worse in OVS (AHI:52 vs 47, ODI:53 vs 43, mean SaO2:89 vs 91, min SaO2 74 vs 78, TST90: 127 vs 84). Additionally, disturbances in sleep architecture were more prominent in OVS as expressed by lower %N3 and REM% and higher arousal index (p<0.001). Independent predictors of OVS were older age, truncal obesity and increased HCO3. <bold>Conclusions:</bold> Our data suggest that OVS is prevalent among OSA patients, with distinct clinical characteristics and more severe OSA disease spectrum. These characteristics could be utilized as predictive factors for further assessment of these patients.