The study, published today in the online issue of Neurology, the medical journal of the American Academy of Neurology, found that older adults who reported either light or no exercise at all experienced a cognitive decline equal to 10 more years of aging when compared to people who were moderate to intense exercisers.
"The number of people over the age of 65 in the United States is on the rise, meaning the public health burden of thinking and memory problems will likely grow," study author Dr. Clinton B. Wright, of the University of Miami, said in a statement. "Our study showed that for older people, getting regular exercise may be protective, helping them keep their cognitive abilities longer."
Wright and his team examined health data on almost 900 adults with an average age of 71. In a questionnaire, participants were asked how long and how often they had engaged in physical activity during the previous two weeks.
An average of seven years later, each subject took tests evaluating memory and thinking skills and got a brain MRI. Five years after that, the participants took the memory and thinking tests again.
In all, 90 percent of the group reported light exercise, such as walking and yoga, or no exercise at all. The remaining 10 percent were categorized as high intensity exercisers and reported participating in activities like running, aerobics, and calisthenics.
After reviewing the data, the researchers found that of the people who had no signs of memory and thinking problems after the first set of cognitive tests, those who reported low activity levels showed a greater decline over five years than their high activity counterparts.
"We found that people who exercise moderately or heavily had a reduced risk of memory loss and what we call executive function, equivalent to about 10 years," study co-author Dr. Mitchell Elkind, professor of neurology and epidemiology at New York Presbyterian/Columbia University, told CBS News.
The difference remained after the researchers controlled for other factors that could affect brain health, including smoking, alcohol use, high blood pressure and body mass index.
Researchers say seniors should try move around as much as they can. "Calisthenics several times a week, playing handball or tennis, even moderate amounts of activity can be a benefit," Elkind said.
The authors note important limitations to the study, including the fact that that they did not collect lifetime patterns of exercise and relied only self-reported information from the participants.
However, they said it provides encouraging information about the benefits of exercise for older adults.
"Physical activity is an attractive option to reduce the burden of cognitive impairment in public health because it is low cost and doesn't interfere with medications," said Wright. "Our results suggest that moderate to intense exercise may help older people delay aging of the brain, but more research from randomized clinical trials comparing exercise programs to more sedentary activity is needed to confirm these results."