Treated stroke (odds ratio [OR] 3.8, 95% confidence interval [CI] 2.0, 7.2), untreated stroke (OR 3.5, 95% CI 1.7, 7.3), and APOE ε4 (OR 2.8, 95% CI 1.7, 4.5) all increased the odds of dementia. The gene discussed is APOE; the disease is stroke disorder.