Overlap Syndrome: Additive Effects Of OSA On The Cardiovascular Damages In Patients With COPD

Objective Co-existence of obstructive sleep apnea(OSA) and chronic obstructive pulmonary disease(COPD) is referred to as overlap syndrome(OS). This study aimed to investigate the prevalence of overlap syndrome in patients with COPD, to conduct a statistical analysis for patients with overlap syndrome and COPD of their variations in demographics, pulmonary function, blood gas analysis, pulmonary artery pressure, plasma NT–pro BNP level and sleep apnea monitoring parameters and to further assess overlap syndrome as a risk factor of cardiovascular system by a comparison to COPD patients. Methods Individuals with COPD were recruited from August 2013 to March 2015. Information on age, gender, body mass index(BMI), smoking status, comorbidities, and exacerbations in the past year was collected. At subjects’ recovery state, sleep apnealink and spirometry, echocardiography, blood gas analysis, plasma NT – pro BNP were performed for statistical analysis. Results We enrolled 82 COPD patients(60 males) with complete data(mean±SD age 71.18±7.38 years, BMI 22.86±1.96 kg/m2) of whom 28 patients(34%) had evidence of OSA. The BMI and frequency of exacerbations of overlap syndrome were significantly higher than COPD patients(P<0.05).Compared with simple COPD patients, FEV1/FVC and FEV1%pre were more serious in overlap syndrome [( 51.91± 12.94)%VS(41.00±12.14)%],(54.98±17.30)%VS(43.39±14.08)% respectively, all P <0.01]. According to the results of blood gas analysis and sleep apnea monitoring parameters, no matter day or night, the OS group showed more serious hypoxemia and hypercapnia than COPD patients. Pulmonary artery pressure and plasma NT-pro BNP levels were observed to be significantly higher in subjects with overlap syndrome than in those with COPD alone [(41.77±11.32) mm Hg VS(29.41±4.96) mm Hg,(408.54±202.61) pg/ml VS(138.80 ± 90.60) pg/ml respectively, all p <0.01)]. After adjustment for age, BMI and smoking history, AHI showed positive correlations with pulmonary artery pressure and NT – pro BNP(r=0.689, 0.489; all p<0.01).Arterial hypertension, diabetes and coronary heart disease were found to be more common in patients with the overlap syndrome. Conclusion Approximately 34% of COPD patients also suffer from OSA. Increased frequency of exacerbations and a positive correlation with obesity was reported in patients with overlap syndrome. Exceptional severity of hypoxemia and hypercapnia and lung function damage and increased pulmonary artery pressure and NT – pro BNP were also found in overlap syndrome, as compared to the simple COPD group. Furthermore, statistical analysis has showed that pulmonary artery pressure and NT – pro BNP level are strongly correlated with AHI, indicating a higher level of damage to cardiovascular system in overlap syndrome.