DNA extraction and SNP genotyping
The SNP and associated information were adopted in this study according to the NCBI dbSNP database (http://www.ncbi.nlm.nih.gov/, http://snpinfo.niehs.nih.gov/). Genomic DNA samples were extracted from peripheral blood samples by the phenol–chloroform method using the TIANamp Blood DNA Kit (TianGen Biotech, Beijing, China) as described previously[29]. Genotyping for the LincRNA-NR_024015(namely, lncRNA TDRG1 ) rs8506 C>T was performed in the 384-well plate using Taqman PCR method[30]. Genotyping was performed blindly to the status of the case or control.