Study says physical fitness tied to 90% drop in women’s dementia risk; that’s great, but don’t overdo it, others caution.

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The News:

Highly fit women in midlife were nearly 90% less likely to have dementia decades later, a prospective study in Sweden found. Over 44 years of follow-up, the adjusted hazard ratio for dementia was 0.12 for women with high cardiovascular fitness and 1.41 for low-fitness women, compared with women of medium fitness, reported Helena Hörder, PhD, of the University of Gothenburg and colleagues. And when highly fit women did develop dementia, it was 11 years later than for women who were moderately fit, the team wrote online in Neurology.

“The most exciting result is that so few in the group with highest fitness developed dementia–namely two persons, or 5%,” Hörder told MedPage Today. “This is compared to 25% among those with medium fitness and 32% among those with low fitness.”

While many observational studies have linked physical activity to preserved cognitive function, few have assessed cardiovascular fitness objectively, Hörder and colleagues noted. Even fewer (the Cooper Center Longitudinal Study is one) have follow-up periods that span decades.

In this study, the researchers tracked a population-based sample of 1,462 women who were evaluated in 1968 when they were 38 to 60 years old. A subsample of 191 women participated in an exercise test and were followed until December 2012 for dementia diagnoses. Women in the exercise test had their cardiovascular fitness assessed through a stepwise-increased ergometer cycling test that was supervised by a physician. They exercised to exhaustion and had their heart rate, electrocardiogram data, blood pressure, respiratory frequency, and perceived exertion recorded.

Dementia incidence was highest, at 45%, in women who needed to have the exercise test interrupted at sub-maximal workload. This could mean that adverse cardiovascular processes in midlife may increase dementia risk, the researchers suggested.

“An interesting mechanism that needs to be further investigated is the direct effects of physical activity and high fitness on brain structures, such as the hippocampus,” said Hörder. “Age-related changes in brain structures might be delayed through positive effects on small vessel circulation, inflammatory mechanisms, and growth factors.”

To translate these findings from a clinical perspective, it’s important to understand the term “fitness,” noted Nicole Spartano, PhD, of Boston University School of Medicine, and Tiia Ngandu, MD, PhD, of the National Institute for Health and Welfare in Helsinki, Finland, writing in an accompanying editorial.

“Fitness is a measure of cardiovascular function, which is strongly determined by genetics, age, sex, and body size, but also is influenced by lifestyle behaviors such as physical activity. (Ref: MedPage Today)

Steve’s Take:

There are many of us who have been touched by dementia, either directly or indirectly in our families or broader social circles. The witnessing of the gradual disappearance of someone right before your eyes–including yourself–is brutal, yet, ultimately, inevitable.

No wonder the admonitions in the medical realm for exercise, for example, as a possible means of staving off such a woeful end. The intricacies behind what can cause dementia are still largely a mystery and highly debated. But this new study offers more evidence that staying fit can keep both our bodies and minds sharp into our later years.

The Swedish study isn’t the first of its kind to suggest that exercise can stave off dementia, though it might be the longest-spanning one, says Gizmodo. An earlier prospective population study in the US of both men and women found that fit middle-aged people were less likely to develop dementia over a 26-year-old period, for instance.

But these studies can’t tell us directly whether exercise is a key driver of preventing dementia, Hörder said. It’s also not clear whether the women who were physically fit at the time of the bicycling test remained that way for the rest of the study period.

Contrary to these findings, randomized trials of people approaching their senior years have only found weak evidence that exercise can keep people’s minds sharp. As a result, researchers have suggested that there’s a certain threshold when exercise stops being particularly protective–in other words, that trying to become fit past a certain age might not be as effective at preventing dementia as being fit throughout most of your life.

Based on their findings, Hörder and her team believe that this threshold can extend to middle age. But it’s an educated hunch that needs more support, she added.

“More research is needed to see if improved fitness could have a positive effect on the risk of dementia and also to look at when during a lifetime a high fitness level is most important,” she said.

At the very least, it’s not the only study as of late to hint that being good on a bike can pay off big later on in life, health-wise.

Counterpoint:

Then there are those whose data caution that women who exercise strenuously may be at greater risk of developing dementia later in life. Citing another study, their reprimand? Don’t overdo it!

Alison Motluk for the University of Toronto Magazine says if you want to stay mentally alert well into old age, you should exercise, exercise, exercise.

“At least, that’s what the popular press would have us believe. For women, however, that may be exactly the wrong advice: new evidence suggests that, on the contrary, strenuous exercise hastens cognitive decline and increases risk of dementia.”

Many studies have found that exercise protects the brain, but until now no study has compared different intensities of exercise. Mary Tierney, a professor of family and community medicine at the University of Toronto, became especially interested in that link after reading about a study where intense physical activity reduced women’s risk of breast cancer–by depleting their estrogen levels.

Estrogen, Tierney knew, protects the brain against cognitive decline. Could highly active women be depressing their estrogen levels enough to have a detectable impact on their cognitive well-being?

Tierney, who is also a senior scientist at Sunnybrook Research Institute, recruited 90 healthy post-menopausal women and asked about the amount and intensity of their physical activity throughout their adult life, in 10-year periods up to menopause.

Strenuous activities included swimming laps, aerobic exercise, playing racquetball and running. Moderate activities included brisk walking, golfing, cycling on street level and playing softball. Tierney and her colleagues calculated the number of hours a week that each woman engaged in both strenuous and moderate activity, in exactly the way the breast cancer study had done.

Then the researchers tested the women on six neuropsychological tests. One, the Rey Auditory Verbal Learning Test, requires a subject to listen to a list of 15 simple words five times. Then, after reading a list of 15 other words just once, the subject is asked to recall the words from the first list. The test is highly predictive of Alzheimer’s disease up to 10 years in advance.

“Women with the highest levels of strenuous exercise did the most poorly,” says Tierney.

Many active women refuse to believe the results. They feel at their peak when running marathons and tearing up the squash court.

“But these results raise the concern that a lot of strenuous exercise may not be good for women,” says Tierney.

Women exercising hard for many hours a week may not be ovulating normally–though they may not know it. This results in lower-than-optimal levels of estrogen being produced.

“Women who engaged in more exercise probably had lower estrogen over their life,” says Tierney.

Bottom Line:

Steve's Take: To avoid the nightmare of #dementia. My plea to my family, friends and anyone else who’s listening? Exercise, #exercise, exercise. Click To Tweet

Women are at greater risk for Alzheimer’s disease than men. Part of the reason is that, after menopause, a woman’s estrogen levels plummet, and she relies on estrogen from other sources.

Tierney’s advice to women?

“Engage in moderate activity as much as you can,” she says. “But drop the iron-woman workout.”

Personally, covering studies like this latest one in Sweden and others, and listening to first-hand accounts, I’ve concluded: 1) there is the undeniable connection between exercise and improved health outcomes, and 2) if we have any choice about it, which we all don’t necessarily get, how do each one of us want to go out.

My Italian friend occasionally proffers, “Steve, may you live to be a hundred, then get hit by a bus.”

Yes, a bus will do just fine. Far better way to exit stage left than the nightmare of dementia. My plea to my family, friends and anyone else who’s listening? Exercise, exercise, exercise. Whatever you can do, no matter how seemingly inconsequential, do a little more.

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