A GWAX done in 2018 used 314 278 participants from the UK Biobank,8 with 14 338 participants reporting paternal and 27 696 participants reporting maternal family history of Alzheimer’s disease or dementia. Participants were excluded if their parents were younger than 60 years, died before the age of 60 years, or if no age was reported. The GWAX summary statistics were then meta–analysed with stage 1 and 2 of the 2013 IGAP GWAS5 for a total sample of 388 324 individuals. This analysis resulted in the identification of 27 susceptibility loci. Despite concerns that GWAX reflect different underlying genetic architecture than case–control studies due to increased phenotypic heterogeneity, the genetic correlation (the proportion of variance in disease liability shared between two traits) between self–reported parental history of Alzheimer’s disease and clinically diagnosed Alzheimer’s disease was high (maternal rg=0·91; paternal rg=0·66), indicating that this GWAX captured the same genetic architecture as a GWAS of clinical Alzheimer’s disease.8,17
