New research may help motivate you to stick to your new year's exercise resolution.

Results of a new study bring some of the most convincing evidence yet that regular exercise does more than trim the waistline.

Every Friday morning, you'll find 92-year-old May Segal immersed in aqua aerobics.

"In the pool with the other people I feel like I'm a little girl," she says.

And new research out of Seattle suggests Segal's water workouts may do more than just make her feel young.

A six-year study of more than 1,700 seniors over 65 finds those who exercised three times per week were up to 40 percent less likely to develop Alzheimer's than their less-active peers.

The latest research suggests it may never be too late to start. Seniors who were the frailest at the beginning of the study reaped the biggest brain boost.

Duke university aging researcher Dr. Harvey Cohen says exercise triggers a number of healthy effects, like increasing blood flow.

"Exercise and physical activity have effects on lowering inflammation and that can actually allow people to function better as they age physically," said Cohen.

"I'm 92 and half the time I don't feel that," Segal said.

More research is needed to better understand how exercise may help protect against diseases like Alzheimer's, but for now researchers say one thing is clear - retirement is no excuse for an idle brain.

Researchers say it doesn't take a lot of exercise to reap the brain benefit. A minimum of 15 minutes, three times per week is enough.

The physical activity included walking, hiking, bicycling, aerobics, or weight training.

Researchers note that along with improving circulation and lowering inflammation, other factors such as increased social interaction may play a role. Previous studies have suggested that people who engage in group activities have a lower risk of memory problems as they grow older.