MONDAY, Feb. 4, 2013 (HealthDay News) -- Being in good shape during your 40s may help lower your risk for Alzheimer's disease and other types of dementia in your senior years. And the better shape you're in, the lower this risk may be, a large new study suggests.
Nearly 20,000 healthy people took a treadmill test to measure their fitness levels when they were middle-aged. Researchers then reviewed Medicare claims data to see who was diagnosed with any type of dementia in their later years. Follow-up lasted an average of 24 years, with patients assessed for signs of dementia at ages 70, 75, 80 and 85.
Those participants who were deemed physically fit via the treadmill stress test were less likely to develop dementia after age 65 than were their counterparts who were less fit, the study showed.
The findings appear in the Feb. 5 Annals of Internal Medicine.
Researchers can't say for certain that it's the exercise or fitness level that protects brain health based on the results of this study. They also can't say how much exercise is needed to reap any benefits.
That said, "this paper tells us that the more fit one is at midlife, the less likely they are to develop dementia," said study author Dr. Laura DeFina, medical director of research at the Cooper Institute, in Dallas.
Most major medical groups recommend 150 minutes of moderate activity or 75 minutes of vigorous exercise per week, or some combination thereof, she said. "The needle has not been pushed far enough on physical activity," DeFina said. "We are not a moving nation at this point, and this is another bit of evidence to encourage people to exercise."
Exactly how exercise may preserve brain function is not fully understood but, "we know that anything we can do to keep our heart healthy is critical to keeping our brain healthy," she said.
Still, DeFina said, it's a good idea to talk to your doctor before you begin a new exercise regimen, especially if you have any health issues.
Study co-author Dr. Benjamin Willis, an epidemiologist at the Cooper Institute, added: "It's never too late to start exercising."
The new findings help solidify the "move-it-or-lose-it" message, according to experts not affiliated with the new study.
Dr. Richard Isaacson, director of the Alzheimer's division at the University of Miami Miller School of Medicine, said: "Based on most recent data, we know that the brain changes that lead to dementia occur 20 to 30 years before the onset of symptoms, so that is the time to make lifestyle changes. If you are worried about developing Alzheimer's or dementia, the time to make healthy lifestyle choices and changes is now."
This includes engaging in regular exercise, eating a healthy low-fat diet and making sure blood pressure and cholesterol levels are where they need to be, he explained.
"There is no magic bullet that will prevent Alzheimer's, but we have evidence that you can reduce your risk," Isaacson said. "This is an excellent study because it uses an objective measure of fitness: the treadmill test," he said.
These results show how fit a person is, not just how much they exercise, he noted.
Dr. Sam Gandy, the associate director of the Mount Sinai Alzheimer's Disease Research Center, in New York City, agreed that exercise can help keep a brain healthy.
"Three 30-minute sessions per week of either brisk walking or weight lifting is the standard recommendation for delaying or preventing dementia," Gandy said. "This is very, very important. The first thing I tell all my patients is to find an exercise they like and do it."
Although the study found an association between midlife fitness levels and later dementia risk, it did not establish a cause-and-effect relationship.
Are you at risk for Alzheimer's disease? Find out at the Alzheimer's Association.