"Many times it's mid-life elevations of cholesterol and untreated hypertension that are associated with Alzheimer's," said Sager, who was not a part of the study.

Sager said this is the first study to show that treating those conditions in patients who already have some dementia can slow the disease.

Vascular risk factors can increase brain cell death and dementia risk either by causing ministrokes and reduced blood supply in the brain or by contributing to the buildup of plaques of beta-amyloid, the protein that is believed to be a major cause of Alzheimer's.

"If you can delay disease progression, you can reduce the number of patients with advanced disease, which is costly," said lead author Yan Deschaintre, a physician with the Research and Resources Memory Center in Lille, France.

While treating any vascular risk factor should seem like standard practice, many times such conditions go untreated in Alzheimer's patients, doctors said.

Doctors and patients can slack off once an older person is diagnosed with dementia, said Diana Kerwin, an assistant professor of medicine at the Medical College of Wisconsin and clinical director of geriatric medicine at Froedtert Hospital.

"People can get nihilistic," said Kerwin, who was not a part of the study. "I'm very aggressive with vascular risk factors."

Kerwin said the study reinforces the idea of cognitive reserve, that even though people may have beginnings of Alzheimer's disease in their brain, they can avoid developing dementia by strengthening their brain health in other ways.

She said she believed that there will be more studies looking at whether treating vascular conditions long before dementia occurs can prevent or delay it by many years.

"You can give them more years of function during the years of their disease," she said.

She said that people want to live long lives, but they also want to maintain their independence.

"The only way to do that is to start (reducing dementia risk) in their 40s and 50s," she said.

"This is not a good picture of our society and there is no evidence that it is going to get any better."