The Endothelium Dysfunction in Patients of Obstructive Sleep Apnea Syndrome

Sleep Apnea, Obstructive

Obstructive Sleep Apnea, CPAP, Endothelium dysfunction, Hypertension

study Hypothesis: We hypothesize that CPAP could effectively improve the endothelial dysfunction by anti-inflammatory effect in patients of OSA,and compare to the effect of statin.

Obstructive sleep apnea is a prevalent disorder that affect 2-4% adults in general population. Cardiovascular and Neurocognitive complication were the most common and severe consequence noted in patients of OSA. Endothelial dysfunction is the early pathologic changes in the vascular wall that precede to the clinical cardiovascular events. Endothelial dysfunction with the deficit of vascular relaxation will induce the development of hypertension. Endothelial dysfunction predict the occurrence of ischemic heart disease and cardiovascular events as stroke. The development of endothelial dysfunction significantly remark the early sign of the development of cardiovascular diseases. Inflammation trigger by oxygen radical in the vascular system were the major pathogenesis of the endothelial dysfunction. Intermittent hypoxia in the patients of OSA during repeated apnea at night will increase the oxygen radicals therefore trigger the cascade of inflammation process. The inflammatory process could be mediated by the activation of the transcription factors such as NF-KB, AP-1 or from the pathway of HIF-1 cascade. Inflammatory cytokine such as HsCRP inducted by the activation of NF-KB and AP-1 will induce the interaction of monocytes and lymphocytes to further injury to the endothelium of vascular wall. TGF-B secreted by lymphocyte will create the remodeling by fibroblast which result in the thickening of vascular wall. Another pathway by VEGF, endothelin 1, or other protein modulated by HIF-1 is also proposed directly injure to the endothelium that cause the following cardiovascular events. CPAP treatment for OSA were shown to lowering the severity of blood pressure and cardiovascular events in some reports. Although the effect for blood pressure lowering is still controversial, Most reports actually showed marginal effect on reducing BP to 2 mmHg by CPAP. There is still part of OSA patients with hypertension not responding to CPAP treatment.Besides of the effect of CPAP treatment, the compliance of CPAP is still a major concerning in the treatment of OSA. 60% of patients were reported to continue used CPAP in the well-supported sleep center in USA. Even the CPAP is covered by reimbursement in USA, the low compliance of CPAP impede the treatment of cardiovascular complication of OSA. To improve the control of the cardiovascular consequence of OSA, a convenient and well-tolerated intervention is mandatory. Statin, a powerful lipid-lowering medication, is found to have a significant anti-inflammatory effect in several reports. Statin is even suggested in the population of normal cholesterol to prevent the development of cardiovascular event. Statins exert cholesterol-independent, anti-inflammatory and immunomodulatory effects. Pleiotropic effects are typically mediated by HMG-CoA reductase inhibition, are dose dependent and occur rapidly after initiation of statin treatment. In order to evaluate and explore a safe and convenient method in the control of the cardiovascular complication of OSA, we conduct this study.

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