Impact of continuous positive airway pressure on C-reactive protein in patients with obstructive sleep apnea: a meta-analysis

C-reactive protein (CRP) is associated with the development of obstructive sleep apnea (OSA) and cardiovascular diseases. Continuous positive airway pressure (CPAP) is an effective treatment for OSA, but the impact of CPAP therapy on CRP levels in patients with OSA remains unclear. To obtain this information, we performed a meta-analysis to determine whether effective CPAP therapy could reduce serum CRP levels. A comprehensive literature search was performed to identify studies that examined the impact of CPAP on serum CRP levels in OSA patients who were treated with CPAP for at least 4 weeks. Standardized mean difference (SMD) was used to analyze the summary estimates for CPAP therapy. Fourteen self-control design studies involving 1199 patients with OSA met the inclusion criteria. Meta-analysis indicated that the overall SMD for the CRP levels was 0.64 units (95 % confidence interval (CI) 0.40 to 0.88) before and after CPAP therapy; test for overall effect z = 5.27 (P = 0.000). Subgroup analysis showed that evolution of CRP decreased non-significantly in less than 3 months (SMD, 0.26, 95 % CI -0.08 to 0.60, P = 0.138), significantly decreased after 3 months (SMD, 0.68, 95 % CI 0.34 to 1.02, P = 0.000), and further declined after 6 months (SMD, 0.74, 95 % CI 0.43 to 1.05, P = 0.000). The systemic inflammation, as measured by CRP, was present and significantly reduced by effective CPAP therapy in patients with OSA. The use of CRP levels may be clinically recognized as a valuable predictor for OSA treatment monitoring.