Sharma S, Gebregziabher M, Parker AT, et al. Clin Cardiol. 2012;35:641–645.
To the Editor:
We read the recently published review article by Sharma et al with interest.[1.] The authors retrospectively studied 81 patients, with 49 having obstructive sleep apnea (OSA). These researchers found that an increase in OSA severity was associated with a greater burden of noncalcified and mixed plaques assessed with multidetector-row computed tomography after adjustment for age, race, smoking, and hypercholesterolemia (odds ratio: 14.2; 95% confidence interval: 1.3-158.5). However, as was mentioned by the authors, several confounding factors such as high blood pressure, use of lipid lowering medications, body mass index, and the presence of type 2 diabetes mellitus were not adjusted in this analysis, because all of these may independently affect coronary circulation.[2.] These factors, and possibly a small sample, may explain the strikingly wide confidence interval received in their study.
Nevertheless, this study provides another piece of information that OSA is likely to be a significant risk factor for vascular disease. The authors mentioned that OSA may mediate vascular dysfunction via its relationship with arterial hypertension, endothelial dysfunction, and dyslipidemia. However, several other factors may contribute to the occurrence of vascular disease among patients with OSA.
First, robust evidence suggests that OSA may act as an independent factor for the occurrence and progression of renal disease.[3.] The presence of renal disease is indeed associated with accelerated progression of atherosclerosis. Second, OSA is believed to contribute to the occurrence and control of type 2 diabetes mellitus, independently from obesity and age.[4.] Third, emerging data point to an independent relationship between nonalcoholic fatty liver disease (an emerging vascular risk factor) and OSA.[5.]
Finally, we want to express our sincere gratitude to the authors for studying this important clinical problem and adding valuable information on the association of OSA with vascular disease. Nevertheless, prospective studies are needed to get a definitive answer on the potential impact of OSA on vascular morbidity and mortality.