Background:Chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) syndrome are highly prevalent respiratory conditions.Their coexistence is referred to as the overlap syndrome.They are both related to pulmonary hypertension (PH) development.This study investigated the effects of OSA on PH in patients with COPD and the associated factors.Methods:Consecutive patients with stable COPD were recruited for an observational cross-sectional study from September 2016 to May 2018 at Peking University Third Hospital.In total,106 patients with COPD were enrolled and performed home portable monitoring and echocardiography.OSA was defined by an apnea hypopnea index (AHI) ≥10 events/h.Based on OSA absence or presence,patients were divided into the COPD with OSA and COPD without OSA groups.Factors affecting pulmonary artery pressure (PAP) and PH were identified using univariate analysis and logistic regression models.Results:In the 106 patients with COPD,the mean age was 69.52 years,91.5％ were men,and the mean forced expiratory volume in 1 s (FEV1) percentage of predicted was 56.15％.Fifty-six (52.8％) patients with COPD were diagnosed with OSA,and 24 (22.6％)patients with COPD were diagnosed as PH.Compared with COPD without OSA group,the median PAP in COPD with severe OSA group increased by 5 mmHg (36.00 [26.00-50.00] mmHg vs.31.00 [24.00-34.00] mmHg,P =0.036).COPD with percent of night-time spent with oxygen saturation below 90％ (Tg0) ＞ 10％ group had higher PAP than COPD with Tg0 ≤ 1％ group (36.00[29.00-50.00)] mmHg vs.29.00 [25.50-34.00] mmHg,F =7.889,P =0.007).Univariate analysis revealed age,FEV1％ predicted,T90,and Charlson index had statistically significant effects on PH.Multiple regression analysis showed a significant and independent effect of both FEV1％ predicted (odds ratio [OR] =3.46;95％ confidence interval [CI]:1.15-10.46;P =0.028) and AHI (OR =3.20;95％ CI:1.09-19.35;P =0.034) on PH.Conclusions:Patients with COPD with OSA are more susceptible to PH,which is associated with declining lung function and increased severity of OSA.Thus,noctal hypoxemia and OSA in elderly patients with COPD should be identified and treated.