WASHINGTON — Treating risk factors such as high blood pressure and diabetes that are more commonly associated with heart disease substantially slowed the progression of cognitive decline in dementia patients, according to a new study that should prompt doctors to be more aggressive in targeting such vascular conditions.

The study also raises the prospect that treating those conditions in people with mild cognitive problems, but not actual dementia, could prevent dementia altogether or at least buy extra years of life without disabling symptoms.

The number of Americans with Alzheimer's disease this year surpassed 5 million and is expected to increase by 450,000 new cases a year, reaching a total of 7.7 million by 2030.

At the same time, the sobering trends of increased life expectancy and greater rates of obesity, diabetes and physical inactivity point to a cognitive health crisis in the coming years, said Julie Gerberding, director of the U.S. Centers for Disease Control and Prevention.

"This is not a good picture of our society, and there is no evidence that it is going to get any better," she said at the conference. "Alzheimer's is an important health concern for a whole lot of families. I'm certainly concerned about it for my family."

Promising research on several new drugs is expected to be presented here this week at the Alzheimer's Association prevention conference, but a study Sunday found that using available drugs to treat diabetes, high blood pressure, high cholesterol, smoking and other vascular conditions considerably slowed the advance of Alzheimer's in patients who already had been diagnosed with the disease.

The study involved 891 dementia patients treated at a memory disorders clinic in France who, on average, had 2.6 of the vascular risk factors. Over the course of more than three years, those who had all their risk factors treated did much better on cognitive tests than those who did not get treatment.

The effect amounted to about a one-year delay in cognitive decline after two years. In other words, those who had all of their vascular risk factors treated took three years to decline as much as those who went untreated for two years.

"A one-year slowdown would be a big deal," said Steven DeKosky, professor and chairman of neurology at the University of Pittsburgh.

It's similar to what the best approved Alzheimer's drugs now provide, said DeKosky, who was not a part of the study.

For several years, doctors have known that various vascular conditions increased the risk of dementia, said Mark Sager, a professor of medicine at the University of Wisconsin-Madison and director of the Wisconsin Alzheimer's Institute.