July 15, 2009 (Vienna, Austria) -- A warning to female marathoners: Long-term strenuous activity may lead to memory loss.
Long-term moderate exercise, such as brisk walking or cycling on level streets, helped women to sharpen their mental skills.
"People often think, if a little is good, a lot is better. But that's not the case here," says researcher Mary C. Tierney, PhD, of the University of Toronto.
The study was presented here at the Alzheimer's Association 2009 International Conference on Alzheimer's Disease.
"The researchers argued that exercise exerted its protective effect by lowering estrogen levels in the body. Since estrogen is known to affect the brain positively throughout a woman's life, we wondered about the effect of exercise on cognitive function," she explains.
Additionally, studies in which rats ran on a treadmill showed that "the further they pushed, the greater the damage to the brain, especially in the hippocampus, the key area for learning and memory," Tierney says.
Strenuous Activity and Memory Loss
The new study involved 90 recently menopausal women ages 50 to 63. They were asked how frequently they engaged in strenuous and moderate recreational activities from high school to menopause.
Strenuous activities included swimming laps, aerobics, calisthenics, running, jogging, basketball, cycling on hills, and racquetball. Moderate exercises included brisk walking, golf, volleyball, cycling on level streets, recreational tennis, and softball.
Eight memory and brain function tests were administered to all participants.
The researchers found that the more strenuous activity a woman did, the worse her cognitive function -- on all eight tests. They did particularly poorly on tests of recall, memory, and attention, Tierney says.
The more moderate activity a woman did, the better her cognitive function on all the tests.
The analysis took into account age, education, smoking, and other risk factors for cognitive impairment.
Still, the findings don't prove that vigorous exercise causes mental decline, and further study is needed, Tierney says.
It could be the strenuous activity itself or some other lifestyle factor shared by these women that is responsible for the negative effect, says Maria Carrillo, PhD, director of medical and scientific relations at the Alzheimer's Association.
Stress, for example, could lead women to work out more intensively, and stress is known to be harmful to brain health, she tells WebMD.
Pending further research, "it wouldn't hurt to do a trade-off," Tierney says. "Don't be sedentary, but don't push yourself too far either. After 15 minutes on the treadmill, take a brisk walk rather than a long run."