Two datasets from the National Institute on Alcohol Abuse and Alcoholism (NIAAA) Intramural program were also used as replication. Participants were recruited under two NIH Institutional Review Board-approved screening and assessment protocols and were comprehensively assessed at the National Institutes of Health Clinical Center (Bethesda, Maryland, USA) between 2005 and 2015. All participants provided written informed consent. Genotyping was conducted at the NIAAA Laboratory of Neurogenetics (Rockville, MD, USA) using the Illumina Human OmniExpress and Human OmniExpressExome arrays. The same quality review and imputation as in COGA were performed. 169 (130 AD cases, 27 controls, 12 not classified) and 100 (36 AD cases, 27 controls, 12 not classified) unrelated AA (NIAAA-AA) and EA (NIAAA-EA) individuals were used in analyses, respectively. Sex and age were included as covariates. Only AA samples were adjusted for the first three PCs because unlike COGA-EA, EA samples in replication and PRS analysis didn’t include non EA individuals.
