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Why You Shouldn't Skip Exercise After 60, Says New Study

Or at any age, for that matter. New science reveals what sweating more does to your brain.
FACT CHECKED BY Alex Daniel

On a global scale, there are roughly 50 million people living with dementia today. Every year, about 10 million new cases are documented, and it's estimated that by the year 2030 that number will reach 80 million. By 2050, there may be as many as 152 million people suffering from a form of dementia.

The most common variety of dementia is Alzheimer's disease. Of the 50 million dementia sufferers mentioned above, 60-70% have been diagnosed with Alzheimer's. This progressive neurological disorder is infamous for its ability to rob individuals of their very identity. It's an awful condition, characterized by loss of lifelong memories, diminished thinking ability, personality changes, and an overall inability to function independently.

Now, if you'd like to bolster your brain's protections against dementia, we've known for some time that a consistent exercise schedule benefits the brain just as much as the body. For instance, this study published in Neuroimage found that exercise actually sparks the creation and maintenance of new neurons in the hippocampus, which is considered the mind's "memory command center."

More specifically, there's also scientific reason to believe that exercise helps prevent Alzheimer's specifically. One comprehensive review of ten studies encompassing over 23,000 people published in Mayo Clinic Proceedings concludes that more active individuals are much less likely to develop Alzheimer's in comparison to those leading a largely sedentary lifestyle.

Still, the exact how behind exercise's brain benefits has remained a mystery—up until now. Groundbreaking new research from Massachusetts General Hospital published in Nature Metabolism, while preliminary, reveals what occurs in the brain on a molecular level when we break a sweat. Read on to learn more about the secret cognitive side effect of exercise. And for more on reaping the benefits of exercise in your older years, check out The One Exercise That's Best for Beating Back Alzheimer's.

1

A Helpful Hormone

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Scientists report that when we exercise our muscles create more of the hormone irisin (named after the Greek god Iris). Upon creation, irisin makes its way to the brain where it boosts both the overall health and functioning capacity of neurons. This results in improved thinking capacity and memory. Study authors even go so far as to say that irisin drives the cognitive benefits of exercise. In light of these findings, they believe irisin may be useful as a form of therapeutic Alzheimer's treatment.

"Preserving cognitive function is a major challenge in an increasingly aging population," says senior study author Christiane Wrann, DVM, PhD, leader of the Program in Neuroprotection in Exercise at MGH. "Exercise is known to have positive effects on brain health, which is why identifying key mediators of those neuroprotective benefits, like irisin, has become such a critical goal of research."

This research was performed in mice, but the findings held up across both healthy rodents and mice diagnosed with the rodent version of Alzheimer's. Importantly, both humans and mice produce irisin in response to exercise. For some great exercises you can do, see these 5-Minute Exercises for a Flatter Stomach Fast.

2

The Research

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Study authors bred a group of mice incapable of producing irisin. Then they brought in another group of normal mice and set both cohorts up with a running wheel. After a few days of cardio, the normal mice showed marked improvements on a series of cognitive tests However, the irisin-deficient rodents didn't experience any notable cognitive boost from their exercise.

When the research team examined rodents' brains more closely, they discovered that even the irisin-deficient mice did, in fact, produce new neurons in response to exercise. But—and it's a big but—the new neurons in the rodents without irisin displayed far fewer synapses and dendrites, which are essential for inter-neuronal communication. In other words, those new brain cells won't be nearly as cognitively beneficial as they would if irisin was involved.

Where were these new neurons located? The hippocampus, which just so happens to also be one of the first brain areas affected by Alzheimer's.

When researchers used chemicals to artificially provide some irisin to the deficient rodents, mice of all ages showed immediate cognitive improvements. Notably, even irisin-deficient mice suffering from a form of rodent Alzheimer's performed better on cognition and memory tests. Additionally, the dementia-diagnosed mice even showed signs of reduced brain inflammation, which is also beneficial in terms of fighting memory loss.

3

Crossing the Blood-Brain Barrier

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When mice without irisin were injected with some of the hormone into their bloodstream, irisin didn't take long to appear in their brains. This confirms that irisin can cross the blood-brain barrier and interacts directly with brain cells. "What makes this study particularly strong is that we show irisin's effect on cognitive function in not one but four different mouse models," explains study co-author Bruce Spiegelman of Dana-Farber Cancer Institute and Harvard Medical School. Dr. Spiegelman discovered irisin in 2012.

It also can't be overstated how promising the effect of irisin is on rodents suffering from advanced Alzheimer's. "This could have implications for intervention in humans with Alzheimer's disease where therapy typically starts after patients have become symptomatic," adds Dr. Wrann.

4

A New Alzheimer's Drug?

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"It's hard to imagine anything better for brain health than daily exercise, and our findings shed new light on the mechanism involved: protecting against neuroinflammation, perhaps the biggest killer of brain neurons as we age," states study co-author Rudy Tanzi, co-director of the McCance Center for Brain Health at MGH.

While a lot of research is still needed, particularly among human subjects, researchers say irisin may one day be developed as a drug for Alzheimer's treatment. They hope to test a pharmaceutical version of the hormone on both mice and people in the future.

"Since irisin does not specifically target amyloid plaques, but rather neuroinflammation directly, we're optimistic it could have beneficial effects on neurodegenerative diseases beyond just Alzheimer's," Dr. Wrann concludes.

All in all, this study is yet another reason why we should all be exercising on a regular basis. It keeps the mind young! And for more exercise news you can use, see here for The One Walking Exercise That Can Predict Your Death Risk, Says Study.

John Anderer
John Anderer is a writer who specializes in science, health, and lifestyle topics. Read more
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