In women, participants who had highest tertile of vitamin D was associated with lower risk of dementia compared to those with lowest tertile of vitamin D among APOE e4 carries (HR = 0.73; 95% CI 0.63–0.85), but not among APOE e4 non-carries (HR = 0.91; 95% CI 076–1.08). The gene discussed is APOE; the disease is dementia.