Soluble P-selectin levels in patients with obstructive sleep apnea: a systematic review and meta-analysis.

PURPOSE: Obstructive sleep apnea (OSA) patients are at increased risk for cardiovascular disease, stroke, atherosclerosis, hypertension, and venous thromboembolism. Elevated soluble P-selectin (sP-selectin) levels are also associated with increased risk of above diseases. But whether sP-selectin levels in OSA patients are higher than their counterparts remain unclear, since previous studies yielded inconsistent results. Therefore, a meta-analysis is warranted. METHODS: PubMed, Embase, Cochrane Library, and Web of Science databases were searched for eligible studies. Studies were included if they reported sP-selectin levels of both OSA patients and non-OSA controls. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated to determine the effect sizes. RESULTS: Nine eligible studies were finally evaluated. When all the studies were pooled, sP-selectin levels in OSA patients were significantly higher than that in controls (SMD = 0.54, 95% CI 0.29-0.78, I2 = 66%, p < 0.0001). In the subgroup analysis based on BMI matched groups, sP-selectin levels were significantly higher in OSA patients than that in controls (SMD = 0.52, 95% CI 0.27-0.76, I2 = 23%, p < 0.0001). In the subgroup analysis stratified by blood source, either serum sP-selectin levels or plasma sP-selectin levels in OSA patients were higher than that in controls. Moderate-to-severe OSA patients had significant higher sP-selectin levels (SMD = 0.80, 95% CI 0.45-1.15, I2 = 67%, p < 0.00001), while mild OSA patients showed no significant difference with controls. CONCLUSION: The pooled results reveal that OSA patients have higher sP-selectin levels than non-OSA controls. This conclusion remains unaltered in all subgroups other than the subgroup of mild OSA patients. Additional studies are warranted to better identify the role of sP-selectin as a potential biomarker in OSA patients.