The role of nitric oxide (NO) levels in patients with obstructive sleep apnea-hypopnea syndrome: a meta-analysis.

ABSTRACT

PURPOSE: The pathogenesis of cardiovascular disease (CVD) in patients with obstructive sleep apnea (OSA) is unclear. Several studies have suggested that CVD may be caused by oxidative stress from chronic intermittent hypoxia and associated vascular endothelial dysfunction. Oxidative stress in patients with OSA can induce endothelial cell apoptosis, aggravate vascular endothelial damage, and promote the expression of redox-sensitive genes and adhesion molecules. No meta-analysis has explored whether or not OSA is related to nitric oxide (NO). METHOD: To assess the association between serum/plasma NO levels and OSA, we performed a meta-analysis of the literature on the subject to grade the strength of evidence. RESULTS: OSA was significantly related to decreased serum or plasma NO levels (WMD = - 11.66, 95% CI - 17.21 to - 6.11; P < 0.01). Among the studies analyzed, there was high degree of heterogeneity (I2 = 79%, P < 0.01). Sensitivity analysis showed that after omitting any single study or converting a random effects model (REM) to a fixed effects model (FEM), the main results still held. CONCLUSIONS: This meta-analysis suggests a strong correlation between OSA and serum or plasma NO levels which may explain the link between intermittent hypoxia of OSA and risk of CVD. The strength of this finding may spur further basic and clinical research into vascular endothelial dysfunction in patients with OSA.