Long-term Effects of CPAP on Lipidemia and Hs-CRP Levels in OSA Patients

Obstructive sleep apnea (OSA) is a common sleep disorder characterized by recurrent episodes of partial or complete obstruction of the upper airway during sleep, resulting in sleep fragmentation and oxyhemoglobin desaturation. OSA is recognized as an important public health problem in developed country, affecting 9 and 24% of middle-aged females and males, respectively. OSA, however, is not recognized as an abnormality for the majority and doesn't get more attention from most people in China. Increasing evidence now indicates that severe OSA is associated with increased cardiovascular morbidity and mortality, mainly due to acute myocardial infarction and stroke. Atherosclerosis is a key mechanism for these cardiovascular events. Numerous studies have explored the relationship between hypertension and OSA. And these studies confirms that OSA is an important identifiable cause of hypertension and a raised blood pressure has been shown to fall with effective continuous positive airway pressure (CPAP) treatment. Dyslipidemia, an established independent risk factor for coronary heart disease (CHD) and atherosclerosis, is common in patients with OSA. But there are limited interventional data on OSA and lipidemia, showing controversial results. Several studies9,10 have shown a direct relationship between OSA and lipid profiles, independently of obesity, while other studies have demonstrated that obesity, as a confounding factor, contributed to dyslipidemia among OSA patients.11,12 Taken together, adiposity is a strong confounding factor for interpretation of the causal relationship between dyslipidemia and OSA. Few studies have focused on nonobese patients.10,13 There are only a small number of randomized trials that have examined the effect of CPAP on fasting lipid profiles14,15 and none were specifically designed to evaluate the lipid profiles. Furthermore, most studies assessed the impact of CPAP on OSA-related lipids without statin therapy. In this way, it may be useful to avoid the disturb conditions due to statin treatment. But it is impractical to those patients with OSA and CHD. Since statins, in addition to decreasing hyperlipidemia levels, also inhibit inflammatory cytokines and play a critical role of plaque stabilization in CHD patients. Similarly, the condition existed in the examination of high-sensitivity C-reactive protein (hs-CRP) in CHD subjects with OSA. Therefore, the aims of the present study were (1) to establish whether CPAP therapy decreases lipid profiles and hs-CRP levels in nonobese patients with CHD and OSA, (2) to establish whether a relationship exists between the severity of OSA and levels of these circulating markers, and (3) to demonstrate a possible mechanism for the prevention of cardiovascular disease.