Female marathoners who hit the roads regularly may look fit and healthy, but once they pass menopause, their brains may lag behind. Surprise! According to a new study from the University of Toronto, women who engage in “vigorous” aerobic exercise for decades experience significant cognitive decline and are at increased risk for dementia. Activities such as running distances, biking up hills, doing aerobics, playing racquetball, and swimming laps all qualify for the brain-drain category.
The research involved 90 women between the ages of 50 and 63, all recently menopausal. Study director Dr. Mary Tierney administered a series of cognitive function and memory tests to the subjects and found that the more heavy exercise the women had done in their lives, the worse they performed on all eight tests. On average, the strenuous exercise group had engaged in 2.5 hours of vigorous exercise weekly. The damage showed up most dramatically in tests of memory, attention, and recall. To add weight to the results, consider that in a separate study involving exercising rats, the longer and farther the rats ran on a treadmill, the “greater the damage to their brains, especially in the hippocampus, the key area for learning and memory.”
Dr. Tierney started her research after reviewing data showing that women who exercise heavily have far lower breast cancer rates than other women. Dr. Tierney recognized that heavy exercise depresses estrogen levels and lowered estrogen would cause reduced cancer rates. But, she realized, estrogen also plays a key role in cognitive function, and she wondered if, in lowering estrogen levels, heavy exercise would impair cognition. And sure enough, she found that the results both on rats and on people do seem to indicate that more exercise equals less estrogen equals reduced brain power. “Estrogen is bad for breast cancer, but good for the brain,” says Dr. Tierney.
The researchers do acknowledge that other factors could be at play. While the most regular and vigorous exercisers might be the most disciplined and motivated women, the researchers point out that it also might be that women with the most stress and chaos in their lives exercise the most in order to burn off stress. According to that line of thinking, stress could be the real culprit, because wherever stress exists, so does decline — both physically and mentally. Also, the study relied on a small group of subjects who self-reported on their own exercise regimens. If any of those subjects did actually have memory loss, asking them to recall how much they exercised over many decades might be a bit counterproductive.
Nevertheless, the results make training for the Ironman seem a bit less glamorous. But what about engaging in less intense exercise? Should you just hang up your sneakers and park by the TV? Not at all! A simultaneous study found that sedentary women also suffer significant mental decline — in fact, the more sedentary, the more sharp the decline. According to that study, moderate exercise — including activities such as softball, brisk walking, golf, volleyball, cycling on level streets, and tennis for an average of 3.2 hours weekly — preserves the brain, particularly in combination with a healthy diet.
This second study followed 3,000 people, ages 70 to 79, for seven years. Those subjects who were consistently sedentary “scored the worst at the beginning [on tests of memory, problem solving, and attention span] and experienced the fastest rate of cognitive decline,” said study director Deborah Barnes of the University of California in San Francisco. Those who started exercising at any age showed improvements in cognitive function, particularly in their ability to quickly process complex information, while those whose exercise level dropped during the seven-year period also dropped sharply in mental performance. And, a third simultaneous study found that Alzheimer’s patients who exercised had a 44% to 59% lowered risk of dying over the four-year course of the study. Even 30 minutes of exercise a week conferred this protective effect.
So to jog or not to jog, that is the question, especially for women. And the answer, from the standpoint of keeping the brain sharp, seems to be yes, absolutely, exercise but in moderation. Plenty of previous studies attest to the benefits exercise confers not only in improving and preserving cognition as people age, but also in preventing depression, reducing cardiovascular events, slowing osteoporosis, countering diabetes, reducing cancer risk, and so on. But just how much exercise should you do to stay in the magic zone where the body gains resistance while the brain resists decay?
The studies that found benefits associated with exercise typically had subjects working out three to five times a week for 30 to 45 minutes at a shot. Then again, other studies have found that, a 30-minute workout doesn’t suffice for maintaining weight loss; and if it doesn’t help with weight loss, it probably also won’t help with diabetes and various cardiovascular issues. For losing and maintaining weight, subjects needed to exercise at moderate levels for an hour at a time, five days a week. Only if you’re already at your ideal weight and you restrict calories will the 30-minute workout suffice.
The answer, then, seems to be longer exercise sessions at lower levels of intensity. On the other hand, a study early this year found that by doing four 30-second sprints on an exercise bicycle every other day for two consecutive weeks, subjects reaped a 23 percent improvement in insulin function. That comes to about 15 minutes of exercise over the two-week period. Then again, the study only looked at improvements in insulin function, not other associated benefits.
Confused? Don’t be. The bottom line is that there are no real shortcuts when it comes to exercise; you need to commit to doing enough, and doing multiple forms of exercise. Running every day won’t cut it. Going to the gym every day and working out with weights every day won’t cut it. You need it all: cardio/aerobic exercise, strength training, weight-bearing exercise, stretching, breathing, and balance — regularly, but in moderation.
Or to paraphrase the Indian sage, Paramahansa Yogananda, “Too much of a good thing is bad. Too much of any material thing is bad. No matter how healthy something is, if you overindulge in it, pain will result instead of benefit.”