Several potential factors influencing on NMR (sex, age, BMI, smoking quantity, alcohol consumption, genotyping batch) [17] were considered as covariates. Sex and BMI were associated with NMR (p<0.05) in the initial linear univariate regression models, and were selected as covariates for the study specific GWAS. Further, age was selected as a covariate due to the sampling design of the population-based samples. Neither smoking quantity, alcohol consumption, nor genotyping batch, were significant confounders (p>0.05) and thus were not included as covariates. Details of phenotype and covariate distributions in the three samples are presented in Table 1.
