Increased Inflammatory Activity in Nonobese Patients with Coronary Artery Disease and Obstructive Sleep Apnea

STUDY OBJECTIVES: Obstructive sleep apnea (OSA) is common in patients with coronary artery disease (CAD). Enhanced vascular inflammation is implicated as a pathophysiologic mechanism but obesity is confounding. We aimed to address the association of OSA with inflammatory biomarkers in a nonobese cohort of revascularized patients with CAD and preserved left ventricular ejection fraction. DESIGN: Cross-sectional analysis of baseline investigations of a randomized controlled trial. SETTING: Clinic-based. PARTICIPANTS: There were 303 nonobese patients with CAD, of whom 213 with OSA (apnea-hypopnea index AHI ≥15 events/h) and 90 without OSA (AHI < 5 events/h). Obese patients with CAD and OSA (N = 105) were chosen as an additional control group. INTERVENTIONS: None. MEASUREMENTS: Circulating levels of high-sensitivity C-reactive protein (hs-CRP), interleukin (IL)-6, IL-8, and tumor necrosis factor-α were assessed in relation to OSA diagnosis based on AHI ≥ 15 events/h as well as oxygen desaturation index (ODI) ≥ 5 events/h. RESULTS: Nonobese patients with OSA had significantly higher levels of hs-CRP and IL-6 than those without OSA. The values did not differ significantly between obese and nonobese patients with OSA. In bivariate regression analysis, AHI ≥ 15 events/h was associated with all four biomarkers but not so in the multivariate model after adjustment for confounders. ODI ≥ 5 events/h was associated with hs-CRP (odds ratio OR 1.49, 95% confidence interval CI 1.13-1.99) and IL-6 (OR 1.30; 95% CI 1.05-1.60) in multivariate analysis. CONCLUSIONS: OSA with ODI ≥ 5 was independently associated with increased inflammatory activity in this nonobese CAD cohort. The intermittent hypoxemia, rather than the number of apneas and hypopneas, appears to be primarily associated with enhanced inflammation.