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Exercise Protects an Aging Brain

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We often write about the cognitive benefits of exercise in this newsletter, and now there’s even more evidence to motivate you to lace up those sneakers. Scientists have long studied how physical activity can reduce the risk of developing dementia as we age, and a new study adds to the growing evidence. What distinguishes this research from previous studies? Read on, and we’ll explain… The newest study tracked the physical movement of hundreds of octogenarians and how it impacted their cognitive health.1 When participants passed away, the scientists discovered some interesting contrasts between the active older people and their more sedentary counterparts. It turns out that certain vital immune cells, called microglial cells, worked differently in active older people’s brains. These cells influenced general brain health, the participants’ thinking abilities, and whether they ultimately experienced the memory loss of Alzheimer’s disease. But first, let’s get a better understanding of microglial cells and why they matter.

The 411 on Microglial Cells 

If you’ve never heard of microglial cells, you’re not alone. Until now, most of the research was conducted with rodents. Microglia are the brain's resident immune cells. They activate to clear debris and foreign invaders from the brain.2 Once invaders are spotted, the cells release chemicals that initiate an inflammatory response, which can help clear away biological debris. Later, the microglia deploy chemical signals that reduce inflammation, keeping the brain healthy. Past research with rodents found that these traffic cop cells start to go a little crazy as the animals age.3 They will initiate the inflammation but not calm it down afterward, which leads to chronic brain inflammation. Scientists found this non-stop inflammation can kill healthy cells and wreak havoc on memory, inducing Alzheimer’s disease… but not if the animals exercise! That link hasn’t been established in humans, until now.

Testing the Theory on Humans 

Scientists at the University of California, San Francisco used data from the Rush Memory and Aging Project, which included hundreds of people from Chicago, mostly in their 80s. These octogenarians completed extensive annual cognitive and memory tests and wore activity monitors. There were a few that formally exercised, the trackers showed. However, more telling is that some people simply moved around, walking a higher number of steps more often than their study peers. Many participants passed away as the study continued, and researchers had an opportunity to examine the brain tissues from 167 of them. During those post-mortem examinations, scientists searched for evidence of microglial activity. Mostly, though, they looked at these people’s microglial cells during their final years of life. Were the cells driving runaway brain inflammation, or had they been able to dial back inflammation when appropriate? And were there any common biomarkers of Alzheimer’s disease, such as plaques and tangles? Next, the scientists compared this data with the data from the participants’ trackers. Here’s what they found out…

More Motion Means Healthier Microglial Cells 

That’s right, microglia from the most active participants featured biomarkers suggesting the cells knew how to calm inflammation when needed, especially in the portions of the brain associated with memory. And their sedentary peers? These unlucky participants showed signs of an unhealthy microglia overdrive during their last years. Notably, these same men and women scored lowest on cognitive tests before death. Interestingly, scientists found that even though the active participants’ brains may have shown signs of Alzheimer’s, their lives and thinking abilities did not reflect that. Study author Kaitlin Casaletto, an assistant professor of neuropsychology at the U.C.S.F. Memory and Aging Center, says these findings suggest that physical activity may delay or alter memory loss from Alzheimer’s disease in older people, due in part to healthy microglia. Equally encouraging, the amount of activity needed to reap these benefits was not huge. In fact, few of the study participants had formally exercised. “But there was a linear relationship between how still they were and their brain health,” she says. “The less they sat, the more they stood, the more they moved around, the better their outcomes.” Are the microglia the only component of the brain that’s influenced by physical activity? Not a chance. Professor Casaletto says movement changes a cornucopia of cells, genes, and chemicals in the brain. Some are more important than others to cognitive health.

My Takeaway 

The study doesn’t prove that activity causes microglia to perform better, but rather healthy microglia are common in active people. Either way, I know that I’ll be opting for movement whenever possible for both my physical and mental health. Daily walks are my favorite, but even puttering around the house doing chores adds to my physical activity tally. What’s your favorite way to “add steps” to your day? Decide and get moving.
  2. activation-to-improve-brain-health-in-Alzheimers-disease.aspx 

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