Taking steps to stave off diabetes and heart disease may improve a person's chances of staying mentally sharp later in life, several research teams said on Monday.

In one study, U.S. researchers found the same cluster of metabolic disorders that raise a woman's risk for heart disease and diabetes also increase her chances of memory declines later in life.

A second study found that a history of diabetes and high cholesterol hasten the rate of mental declines in people with Alzheimer's disease.

"Preventing heart disease, stroke and diabetes - or making sure these conditions are well managed in patients diagnosed with them - can potentially slow the disease progression of Alzheimer's," said Yaakov Stern of Columbia University Medical Center, whose study was one of several on metabolic diseases and dementia published in the Archives of Neurology.

The findings build on recent studies that suggest people who take cholesterol-lowering drugs known as statins have a lower risk of developing all forms of dementia. And diabetics who take pills that help their bodies use insulin better have a lower risk of Alzheimer's.

Now many teams are trying to get a better understanding of how these disorders affect Alzheimer's disease and other forms of dementia.

Researchers at the University of California San Francisco and the San Francisco Veterans' Affairs Medical Center studied the effects of heart risk factors such as abdominal fat, high blood pressure and low levels of good cholesterol, known collectively as the metabolic syndrome.

Dr. Kristine Yaffe and colleagues followed 4,895 women with an average age of 66 who had no memory problems or other cognitive impairment at the beginning of the study.

Of the nearly 500 women in the group who had metabolic syndrome, 36 percent developed cognitive impairment during the four-year study period, compared with just 4 percent of the 4,400 women who did not have metabolic syndrome.

The team said future studies need to focus on whether modifying behaviors could reduce these risks.

Stern and colleagues at Columbia looked to see whether cholesterol levels and a history of diabetes affected the progression of Alzheimer's disease in 156 older patients over 10 years.

After an average of three and a half years, those with higher levels of low-density lipoprotein or LDL cholesterol - the so-called bad cholesterol - declined more quickly than those with normal cholesterol readings.

"These findings suggest that perhaps dealing with some of these metabolic vascular issues early in life might help," Stern said in a telephone interview.

"Even if people have Alzheimer's disease, this is one thing people might want to try to slow its progression," he said.

Alzheimer's disease is the most common form of dementia among older people, affecting 5.2 million people in the United States and 26 million globally, according to the Alzheimer's Association. There is no cure for Alzheimer's, and current drugs merely delay symptoms.