(N = 171) and thus limited power to detect association, we restricted the meQTL analyses to 158 CpG sites with reasonable variance (interquartile range ≥0.05; S2 Fig). We constructed linear regression models of DNA methylation levels at each CpG site as the dependent variable and dosage of coded allele at each SNP as the explanatory variable while adjusting for age and sex, as previously suggested [48, 49]. To account for multiple testing we used the Benjamini and Hochberg method [50] and considered false discovery rate (FDR) corrected p-values below 0.05 as statistically significant. Five CpG sites mapped to CYP2A6 in the genome-wide methylation data; however, we were unable to scrutinize these as four probes were filtered out based on the quality control criteria and the fifth probe had a low (0.02) interquartile range.
