Overweight and obesity are epidemic in Western societies and constitute a major public health problem owing to adverse effects on vascular health, including heart disease, hypertension, stroke, and diabetes mellitus. At the same time, more studies are showing that vascular factors may play a role in the development of Alzheimer disease (AD). The relationship between overweight and AD was examined in a longitudinal population-based study of 392 nondemented Swedish adults, aged 70 years, who were followed up to age 88 years. Women who developed AD between ages 79 and 88 years were overweight, as indicated by a higher average body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters), at ages 70, 75, and 79 years compared with nondemented women. After adjustment for a variety of factors, it was found that for every 1.0 increase in BMI at age 70 years, risk for AD increased by 36%. These data suggest that overweight at older ages is a risk factor for dementia, particularly AD, in women. This may have profound implications for dementia prevention.