Here we conducted a genetic meta-analysis on delirium using multi-ancestry data from the UK Biobank, FinnGen, All of Us Research Program and Michigan Genomics Initiative cohorts (n = 1,059,130; 11,931 cases), yielding the Apolipoprotein E (APOE) gene as a strong delirium risk factor independently of dementia. The gene discussed is APOE; the disease is delirium.