TUESDAY, July 14, 2009 (HealthDay News) -- Eat right, exercise and hope that your genes don't predispose you to dementia.
That's the recipe for preserving cognitive function as you age, according to four new studies that were presented this week at the Alzheimer's Association annual meeting, in Vienna.
The findings echo other research suggesting that clean living can safeguard mental sharpness. However, one of the studies did contain a surprise finding -- that strenuous exercise actually impaired cognitive skills later in life.
That should be viewed, for now, with some skepticism, said William Thies, chief medical and scientific officer of the Alzheimer's Association.
"That's something I wouldn't take on faith from a single study," he stressed.
But the heart-healthy diet advice seemed sound, he said, and confirms other research. In that study, Heidi Wengreen, an assistant professor of nutrition at Utah State University, asked 3,831 adults, aged 65 and older, to complete a food survey. They then tested their cognitive skills over an 11-year period, beginning in 1995.
The researchers looked to see how well the participants followed the DASH diet, an eating regimen that protects against hypertension and heart trouble. Those who followed the DASH diet more closely had higher scores on the cognitive tests at the start of the study and over time, Wengreen found.
Although Wengreen said more study was needed, "I believe there is plenty of evidence to suggest that diet plays a role in delaying cognitive decline and perhaps preventing Alzheimer's disease among the elderly."
Two exercise studies found staying active can also help.
In one study, Deborah E. Barnes, of the University of California, San Francisco, followed more than 3,000 adults aged 70 to 79. Those who were sedentary had the lowest level of cognitive function at the start and higher rates of decline over the course of the seven-year study.
A third study found moderate long-term exercise helped cognitive skills later, but that strenuous long-term exercise might hamper them.
Mary Tierney, a professor of family and community medicine at the University of Toronto, evaluated 90 women, aged 50 to 63, taking into account their long-term activity, both moderate and strenuous. Each woman got a score for strenuous and moderate activity.
Strenuous activities included swimming laps, aerobics, calisthenics, jogging, running, basketball, biking on hills and racquetball. Moderate included brisk walking, golf, volleyball, cycling on level streets, tennis and softball.
"The average long-term strenuous activity was for 2.5 hours a week, and the average long-term moderate activity was 3.2 hours a week," Tierney said.
"The worst groups [on cognitive function tests] were the ones highest in strenuous and lowest in moderate," she said.
Exactly why the link showed up isn't known, she said. But it may be that the strenuous exercise is lowering estrogen levels and lowered estrogen lowers cognitive skills. "Estrogen is bad for breast cancer, but good for the brain," Tierney explained.
It's impossible to say how much exercise is too much, Tierney added.
Yet another study in which researchers followed nearly 1,800 men and women aged 60 and older found that physical activity boosts cognitive function, except in those who carried the so-called Alzheimer's gene, known as APOE-e4.
Thies said the study on the DASH diet may be especially valuable because the diet gives detailed information about what to eat and the plan is widely available.
The link found between strenuous exercise and lowered cognitive skills may be explained by something else in future research, he said. "You could propose that people who exercise perhaps are a little more tired when they take the test," Thies noted.
"I think the general recommendation that exercise is good [for cognitive skills] is still valid," he said.
Here are the details of the DASH Diet.