While the nearly 20 percent greater risk of vascular dementia was noted among women compared to men with diabetes, the risk for nonvascular dementia (predominantly Alzheimer's disease) associated with having diabetes was roughly the same in both genders -- but still 40 percent higher than for people without diabetes.

Huxley said it's still not clear to scientists why type 2 diabetes may increase the chances of dementia, regardless of gender.

"It's a good question but one to which we don't have a definitive answer," she said. "Some studies suggest that vessel damage in the brain caused by diabetes is an important factor."

Dr. James Ellison, the Swank Foundation endowed chair in memory care and geriatrics at Christiana Care Health System in Wilmington, Del., said it's well-known that diabetes damages blood vessels, and that aging of the blood vessels is a major contributor to the development of vascular dementia.

"But why it should be a more serious risk for women than men isn't readily apparent," said Ellison, who wasn't involved in the new study. "The message to clinicians is to consider screening aggressively for diabetes and prediabetes and to be very attentive to women who are in higher risk groups, like women with gestational diabetes." Gestational diabetes is pregnancy-related.

Huxley said people with diabetes shouldn't panic about dementia, noting that many healthy lifestyle measures can offset risks.

"Individuals at risk of developing diabetes and those with overt diabetes can do many things to reduce their risk of dementia, such as quitting smoking, increasing the level of physical activity, eating a healthy diet, minimizing alcohol intake and even losing a few pounds," she said.

"The take-home message is that for many people -- with and without diabetes -- dementia is not inevitable," Huxley added. "Maintaining a healthy weight, watching what you eat and keeping your brain fit and active are some of the things that may reduce future risk of dementia. There's some truth in the adage, 'A healthy body equals a healthy mind.'"