Protective Cardiovascular Effect of Sleep Apnea Severity in Obesity Hypoventilation Syndrome.

<bold>Background: </bold>Obesity hypoventilation syndrome (OHS) is associated with a high burden of cardiovascular morbidity (CVM) and mortality. The majority of patients with OHS have concomitant OSA, but there is a paucity of data on the association between CVM and OSA severity in patients with OHS. The objective of our study was to assess the association between CVM and OSA severity in a large cohort of patients with OHS.<bold>Methods: </bold>In a cross-sectional analysis, we examined the association between OSA severity based on tertiles of oxygen desaturation index (ODI) and CVM in 302 patients with OHS. Logistic regression models were constructed to quantify the independent association between OSA severity and prevalent CVM after adjusting for various important confounders.<bold>Results: </bold>The prevalence of CVM decreased significantly with increasing severity of OSA based on ODI as a continuous variable or ODI tertiles. This inverse relationship between OSA severity and prevalence of CVM was seen in the highest ODI tertile and it persisted despite adjustment for multiple confounders. Chronic heart failure had the strongest negative association with the highest ODI tertile. No significant CVM risk change was observed between the first and second ODI tertiles. Patients in the highest ODI tertile were younger, predominantly male, more obese, more hypersomnolent, had worse nocturnal and daytime gas exchange, lower prevalence of hypertension, better exercise tolerance, and fewer days hospitalized than patients in the lowest ODI tertile.<bold>Conclusions: </bold>In patients with OHS, the highest OSA severity phenotype was associated with reduced risk of CVM. This finding should guide the design of future clinical trials assessing the impact of interventions aimed at decreasing cardiovascular morbidity and mortality in patients with OHS.<bold>Trial Registry: </bold>Clinicaltrial.gov; No.: NCT01405976; URL: www.clinicaltrials.gov. [ABSTRACT FROM AUTHOR]