ObjectiveTo analyze the clinical characteristics of patients with chronic obstructive pulmonary disease (COPD) and COPD overlapping obstructive sleep apnea hypopnea syndrome (overlap syndrome), and to study the relationship between overlap syndrome and cardiovascular diseases.

MethodsA total of 126 stable COPD patients admitted to the Respiratory Department of Peking University Third Hospital from September 2016 to October 2018 were included in this study, including 112 males and 14 females, ranging in age from 48 to 89 years, with a median of 67 years. With apnea hypopnea index (AHI) 5 times/h for the cutoff value, we classified the patients into a simple COPD group (31 cases) and an overlap syndrome group (95 cases), and compared the patients′ demographic characteristics, respiratory symptoms, lung function, the incidence of cardiovascular events and the cardiac function with echocardiography (E/e′), left atrium diameter (LAD) and left ventricular ejection fraction (LVEF), by using independent-samples T test and chi-square test.

ResultsThere were no statistically significant differences in demographic characteristics, respiratory symptoms, pulmonary function, cardiac function between COPD patients and overlap syndrome patients, but significant differences in blood oxygen level at night and left ventricular mass index(LVMI) between these groups ( P=0.014, P<0.001, P<0.001, P<0.001, P=0.047, respectively) were observed. By comparing the severe sleep apnea hypopnea syndrome (AHI≥30) with sleep apnea hypopnea syndrome patients(AHI<30), there were statistically significant differences in echocardiographic indicators, among which there were statistically significant differences in E/e′( P=0.013), LAD( P=0.006), LVMI ( P=0.051) and LVEF ( P=0.030).There were also significant differences in the history of coronary heart disease and congestive heart failure between the two groups ( P=0.025, P<0.001). After dividing the patients with overlap syndrome by mild, moderate and severe severity, E/e′ and LAD were significantly correlated with severity ( P=0.045, P=0.011). In terms of blood oxygen level at night, there was a significant correlation between average blood oxygen saturation at night and E/e′, LAD, and LVMI ( r=-0.195, P=0.033; r=-0.197, P=0.030; r=-0.195, P=0.044); moreover, there was also a significant correlation between the ratio of blood oxygen≤90% and LAD ( r=0.209, P=0.021). In the multiple linear regression model, E/e′ increased by 0.070 on average for each unit increase in AHI, and 0.084 on average for each unit increase in oxygen desaturation index (ODI).

ConclusionsPatients with COPD overlapping severe sleep apnea hypopnea syndrome showed worse left diastolic function and higher risk of congestive heart failure and coronary heart disease compared with the patients with COPD alone. In addition, the degree of impairment of left heart diastolic function was associated with the severity of COPD overlapping sleep apnea hypopnea syndrome. The higher the AHI and the ODI became, the more severe the left heart diastolic restriction and structures changed.