Although the age range of this sample was quite large, it is known that individual differences relative to age‐group averages are moderately to highly stable, even over longer periods (Gasser et al., 1985; Smit et al., 2005). In order to maximize sample size, subjects were not excluded. However, age was carefully corrected for by including age group and/or age and age2 as covariates. As a consequence, all SNP effects in this study will mostly reflect the genetic effects that are stable across the lifespan. Full details on covariates and demographics for each cohort are given in the Supporting Information Methods.
