Genome-wide association analyses were conducted in each study independently using linear regression (under an additive model) and including sex and age as covariates. For those studies that used IMPUTE software to impute missing genotype data, association analyses were conducted in SNPtest, taking the uncertainty of the imputed genotypes into account.61 For the studies that used MACH to impute their data, either MACH QTL or Merlin was used for association analyses. For the three studies with related individuals (SardiNIA, ERF and QIMR), association analyses were performed in Merlin using a variance components approach, which takes into account the relatedness among individuals in these samples.62
