R [43] was used to fit linear and logistic regression models using established covariates for BMI including PCs associated with BMI and ancestry, sex and age. AD and ND were also included as covariates since the SAGE sample was selected for these traits. Predictors in linear models were included in a stepwise process and independent variables were centered to facilitate interpretation of effects. Interactions between covariates and predictors were tested and included in the final model if the p-value of the interaction was less than the Bonferroni corrected significance level of 0.002.
