Although he is 82 years old, Warren Raymond still exercises several times a week.
"It's helped me in any number of ways. It enhances my self-esteem, improves my physical conditioning," Raymond said.
Raymond was one of 1,700 volunteers in a study that showed exercise also may be good for mental conditioning as well.
In a study published in the latest issue of the Annals of Internal Medicine, volunteers 65 years and older were given a battery of memory tests and questioned about their weekly exercise habits.
After six years, researchers detected a remarkable pattern. Seniors who were physically active at least three time a week were 38 percent less likely to develop Alzheimer's disease, which causes a slow, irreversible decline in brain function.
"It says the decline the brain experiences late in life is not inevitable. It can be affected by things like habitual exercise," said lead study author Dr. Eric Larson of the Group Health Coopertive in Seattle.
In the study, "exercise" was anything from simple aerobics to walking or hiking to 15 minutes of stretching.
Researchers emphasize that this study is not proof that exercise reduces the risk of Alzheimer's disease, but they say the results are consistent with several previous studies.
The theory is that exercise not only increases blood flow and oxygen to the brain -- it may also reduce the telltale "plaque" in the brain associated with Alzheimer's disease.
A recent mouse study comparing the brains of sedentary mice to those put on a running wheel found that the plaques were about a third less in the exercise mice.
"This lends some actual physiological support that there might be a direct mechanism between exercise and the development of plaque," said Dr. Ronald Petersen of the Mayo Clinic.
Meanwhile, Warren Raymond has seen all the evidence he needs.
"It has not always been easy for me to exercise. It's a matter of discipline. I'm just determined to do it."