Researchers found "a striking relationship" between being overweight at age 70 and developing the mind-robbing dementia 10 to 18 years later.
"I think that what it means is that overweight and obesity continue to be a public health problem" and that as women age it's "still something that women need to be concerned about in relationship to their health risks," lead author Deborah Gustafson said.
The researchers said their report supports others that suggest vascular factors play a role in the cause of Alzheimer's. But the Chicago-based Alzheimer's Association cautioned that more research needs to be done.
"These studies often give us clues for areas to look at, but they are not by themselves conclusive evidence that these are the true relationships," said Zaven Khachaturian, a senior science adviser with the association.
The study, published in Monday's Archives of Internal Medicine, looked at the relationship between dementia and body-mass index, or BMI — a height-to-weight ratio. It included 392 Swedish women and men who were followed from age 70 to 88 as part of a geriatric population study in Sweden.
The connection between large body size and dementia was found only in women. The study's analysis focused mainly on women because of a small number of men in the sample.
The study found that women who were diagnosed with dementia between the ages of 79 and 88 were overweight, with a higher average BMI at ages 70, 75 and 79, compared with women without dementia.