TLR6 and obstructive sleep apnea syndrome: Summary of results of multivariate linear regression and multiple comparison: OSA is the independent risk factor of DNA methylation levels over CpG site #1, #2, #3, #18, #25 and #28 of the TLR2 promoter region, CpG site #1 and #3 of TLR6 gene body, and protein expression of TLR6.