Roles of interleukin (IL)-6 gene polymorphisms, serum IL-6 levels, and treatment in obstructive sleep apnea: a meta-analysis

Background Inconsistent results regarding the relationship between interleukin (IL)-6 gene polymorphisms, serum IL-6 levels, and the treatment in obstructive sleep apnea (OSA) have been reported. This meta-analysis assessed the associations between IL-6 gene polymorphisms and OSA susceptibility, IL-6 levels in OSA, and CPAP (continuous positive airway pressure) and T&A (tonsillectomy and adenoidectomy) therapy for IL-6 in OSA. Methods Studies regarding IL-6 polymorphisms, serum IL-6 levels, and OSA treatment were identified using PubMed and Embase. The associations between IL-6 gene polymorphisms and OSA risk (estimated by pooling odds ratios (ORs) with 95 % confidence intervals (CIs)) were assessed using an allele model. The pooled standardized mean differences (SMDs) with 95 % CI of IL-6 were estimated using a random-effects model. Meta-regression, sensitivity analysis, and publication bias were also evaluated. Results In total, 53 studies were included. In adults, a significant association between -174 G/C and OSA susceptibility was observed (OR = 1.46, 95 % CI = 1.14–1.87) and IL-6 levels were higher in OSA compared to controls (SMD = 1.56, 95 % CI = 1.18–1.95); however, no association was observed for the -572 G/C allele (OR = 1.13, 95 % CI = 0.87–1.47) and OSA susceptibility and there was no significant change in IL-6 in pre- and post-CPAP therapy (SMD = −0.24, 95 % CI = −0.73 to 0.26). In children, IL-6 levels were also higher in OSA (SMD = 1.27, 95 % CI = 0.29–2.26) and T&A treatment significantly decreased them (SMD = −0.97, 95 % CI = −1.72 to −0.22). Conclusions This meta-analysis indicates that the IL-6 gene polymorphism -174 G/C, and not -572 G/C, is associated with adult OSA risk. Although IL-6 levels increased in OSA, CPAP did not significantly suppress them in adults with OSA. In children with OSA, IL-6 levels also increased and T&A therapy significantly decreased them.