The study results suggests that regular exercise may be protective, preserving cognitive skills longer, and delaying disorders such as Alzheimer's, Wright said.

"It seems like we're not going to get off easy. There's increasing evidence that it needs to be exercise that gets your heart rate up," he adds.

The study followed people who practiced different exercise patterns, from essentially no regular exercise to very active exercise regimens such as running, racquet sports, and swimming. The group members were first tested for cognitive abilities at age 71; then more recently, after five years passed, they were tested again. MRI scans were used to pinpoint signs of early mental deterioration.

The 10 percent of participants who followed moderate or very active exercise regimens scored far better on cognitive tests than did those who didn't work out. The aging of the brains of the groups showed a different of about 10 years, although they were chronologically the same general age.

"We found that those with moderate-heavy activity had higher baseline scores and slower decline in comparison to inactive patients," the study reported. "The degree of decline was equivalent to the expected decline associated with approximately 10 years of cognitive aging."

The researchers were careful to avoid attributing too much of the relative cognitive abilities of the different groups to their exercise practices. They noted that many other factors can influence cognitive deterioration. To attempt to further define the role exercise plays in brain health, Wright's team is currently studying the effects of exercise on stroke victims.