Background: Sleep-disordered breathing (SDB) is associated with clinical cardiovascular disease (CVD), but its relation to subclinical atherosclerosis remains to be determined.
Methods: We analyzed the cross-sectional associations of SDB, measured by the respiratory disturbance index (RDI), a hypoxemia index, and an arousal index, with carotid plaque and carotid intima-media thickness (IMT), measured by ultrasound. The sample included 985 participants in the Sleep Heart Health Study (mean age-62, median RDI-8.7) with no history of coronary heart disease and stroke, of whom 396 had evidence of a carotid plaque.
Results: As compared with the first quartile of the RDI (0-1.2), the crude odds ratio for carotid plaque was 1.14, 1.27, and 1.48 for the second (1.3-4.1), third (4.2-10.7), and fourth (>10.7) quartile, respectively. After adjustment for CVD risk factors, the corresponding odds ratios were reduced (1.00, 1.04, 1.07, and 1.25). Similarly, the unadjusted mean carotid IMT increased with RDI, but adjusted means (mm) were similar (0.84, 0.85, 0.84, 0.85). Spline regression models did not show monotonicity of the dose-response functions at the right end of the RDI distribution. Neither the hypoxemia index nor the arousal index was associated with carotid plaque or carotid IMT.
Conclusion: The results of this study suggest that crude, positive associations between SDB and subclinical atherosclerosis can be attributed to confounding by CVD risk factors.