Association between elevated endocan levels and obstructive sleep apnea hypopnea syndrome in Turkey and China: A meta-analysis

Background: Endothelial dysfunction has been implicated in the pathogenesis of obstructive sleep apnea-hypopnea syndrome (OSAHS). Previous research has linked endothelial dysfunction to the vascular pathology marker endothelial cell-specific molecule-1 (endocan). This meta-analysis compared endocan concentrations among adult patients with OSAS and controls, and ascertained whether any differences exist. This study aimed to highlight the association between high endocan levels and OSAHS.

Methods: A comprehensive, systematic literature search of the PubMed, Cochrane Library, China National Knowledge Infrastructure, Web of Science, Embase, and Wan Fang databases for relevant studies, published between January 2000 and June 10, 2013, was performed. Additionally, standardized mean differences, correlation coefficients, and adjusted odds ratios were used to assess the effect size. Statistical analyses were performed using R version 4.13 (Copenhagen: The Cochrane Collaboration) and Stata version 10.0 (StataCorp LLC, College Station, TX).

Results: Twelve studies fulfilled the inclusion criteria. Nine studies reported endocan levels in patients with OSAHS and controls, and 6 reported serum endocan levels in relation to polysomnography (PSG) indexes (apnea-hypopnea index, body mass index, minimum oxygen (O2) saturation, and flow-mediated dilatation [FMD]). Five studies reported that serum endocan levels functioned independently as risk factors for OSAHS. These levels were determined to be elevated in adults with OSAHS compared with controls (standardized mean difference 1.30 [95% confidence interval (CI) 1.06-1.54]) and increased more significantly with increasing disease severity in individuals with OSAHS. Subjects were divided into different subgroups based on race, geographical region, sample type, and study design. Results indicated increased endocan levels across all OSAHS subgroups compared with the control group. The data highlighted a positive association between serum endocan levels and apnea-hypopnea index, and a negative association with FMD and minimum O2 saturation. The overall adjusted odds ratio between serum endocan levels and OSAHS was 1.04 (95% CI 1.02-1.06).

Conclusion: Results of this meta-analysis provide further evidence supporting elevated endocan levels in adults with OSAHS. Serum endocan levels were correlated with various PSG indices and may be associated with OSAHS.