Age at menarche showed a normal distribution. In each GWA study, linear regression was carried out (assuming an additive model) to test the association between each SNP and age at menarche using PLINK (CoLauS) or SAS/Genetics 9.1 (EPIC-Norfolk). Subsequently, summary statistics of the SNP-menarche age associations of each GWA study were combined in meta-analyses using the inverse variance–weighted method with a fixed-effects model using SAS 9.1. The overall results of the meta-analysis were visualized using HAPLOVIEW.
