How Physical Activity Can Protect Elders’ Brains

Staying physically active as you age substantially reduces your lifetime risk of developing dementia—and you don’t need to exercise for a long time. Walking or moving instead of sitting can be all that’s needed to help strengthen the brain. A new study of octogenarians in Chicago (USA) may help explain why.

The study tracked how often elderly people moved or remained seated and examined their brains in depth after they died. Certain vital immune cells have been found to operate differently in the brains of physically active elderly people compared to their more sedentary peers.

Physical activity appears to have influenced the participants’ brain health, their ability to think, and their likelihood of suffering from the memory loss that arises from Alzheimer’s disease. The findings add to the growing body of evidence that when we move our bodies, we change our minds, no matter how advanced we are.

There is already plenty of scientific evidence indicating that physical activity makes the brain grow. For example, sedentary seniors who start walking for an hour most days often add volume to their hippocampus, the brain’s memory center, reducing or reversing the shrinkage that otherwise commonly occurs over the years.

Middle-aged and older physically active people also tend to perform better on tests of memory and cognitive skills than similar-aged people who rarely exercise, and are nearly 50% less likely to be diagnosed with the condition. of Alzheimer’s. Also, active people who develop dementia often experience the onset of dementia years later than sedentary people.

But precisely how movement reshapes the brain is still largely unknown, although scientists have evidence gleaned from animal experiments. When mice and laboratory rats run on wheels, for example, they stimulate the production of hormones and neurochemicals that promote the creation of new neurons, as well as synapses, blood vessels and other tissues that connect and nourish those young brain cells.

Studies also show that among rodents, physical activity delays or halts aging-related brain decline, in part by strengthening specialized cells known as microglia. Microglia were poorly understood until recently, but today it is known that they are the resident immune cells and the “beyalists” of the brain. They are alert to pick up signs of weakening neuronal health, and when declining cells are detected, they release neurochemicals that initiate an inflammatory response.

In the short term, inflammation helps eliminate problem cells and other biological waste. The microglia later release other chemical messages that calm the inflammation, keeping the brain healthy and tidy and keeping the animal’s thinking capacity intact.

But recent studies have found that when animals get older, their microglia can start to malfunction, initiating inflammation but not subsequently quieting, which leads to ongoing brain inflammation. This chronic inflammation can kill healthy cells and cause problems with memory and learning — problems that can be serious enough to induce a gnawing version of Alzheimer’s disease.

Unless the animals exercise. In this case, “post-mortem” examinations of their tissues reveal that their brains were generally full of healthy and useful microglia well into old age, exhibiting few signs of ongoing brain inflammation, while the elderly rodents themselves retained typical memory and learning abilities. young animals.

But we are not mice, and although we do have microglia, scientists have so far not found a way to study whether physical activity in old age would influence their inner workings. So for the new study, which was published in November in the Journal of Neuroscience, scientists at Rush University Medical Center in Chicago, the University of California San Francisco, and other institutions used data from the comprehensive Rush Project on Memory and Aging.

For this study, hundreds of Chicagoans, mostly in their 80s when the study began, completed extensive annual thinking and memory tests and wore physical activity monitors for at least a week. Few of them exercised formally, as the monitors showed, but some moved or walked much more often than others.

Many of the participants died during the course of the study, and the scientists examined stored brain tissue from 167 of them for remaining biochemical markers of microglia activity. They wanted to see whether people’s microglia seemed to have been constantly overexcited in their final years, causing brain inflammation, or whether they had managed to reduce their activity when appropriate, calming the inflammation. The researchers also looked for common biological clues to Alzheimer’s disease, such as the typical plaques and tangles that are abundantly present in the brains of Alzheimer’s patients. Then they compared this data with information from people’s activity monitors.

They found a strong correlation between physical movement and healthy microglia, especially in the parts of the brain involved in memory. The microglia of the most active elderly, men and women, contained biochemical markers indicating that the cells knew how to be quiet when necessary. But the microglia of sedentary participants showed signs of constant overactivity, an unhealthy pattern, in their final years of life. These sedentary men and women also generally scored lower on cognitive tests.

But what is perhaps most interesting is that these effects were greatest in people whose brains showed signs of Alzheimer’s disease when they died, regardless of whether or not they had major memory loss in life. If these people had been sedentary, their microglia tended to look quite dysfunctional and their memory tended to be patchy. But for people who moved frequently in old age, their microglia generally looked healthy after their death, and many of these people had not suffered major memory loss in their later years. Your brain may have shown signs of Alzheimer’s, but the disease has not manifested in your life or your cognitive abilities.

“These findings suggest that physical activity can delay or alter the memory loss caused by Alzheimer’s disease in older people, in part by keeping microglia healthy,” said professor of neuropsychology Kaitlin Casaletto of the Center for Aging and Memory at the University of California at San Francisco, which led the new study.

Encouraging fact, said Casaletto, the amount of physical activity needed to obtain these benefits was not great. None of the participants ran marathons at the end of their lives. Few of them practiced physical activity formally. But, said Casaletto, “there was a linear correlation” between his degree of inactivity and his brain health. “The less they sat, the more they stood, the more they walked, the better their results.”

The study is important, said Mark Gluck, a professor of neuroscience at Rutgers University in New Jersey, who was not involved in the research. Noting that more research is needed on living people, he said the study’s findings are “the first to use ‘post-mortem’ analyzes of brain tissue to show that a marker of inflammation in the brain, microglial activation, appears to be the mechanism with which physical activity can reduce brain inflammation and help protect against cognitive deterioration caused by Alzheimer’s disease.”

Also, said Casaletto, no one thinks microglia are the only aspect of the brain affected by movement. Physical activity modifies countless other genes, cells and brain chemicals, she said, and some of those effects may be more important than microglia in keeping us mentally sharp. The study doesn’t even prove that physical activity makes microglia work better, it just proves that healthy microglia are common in physically active people. In conclusion, the study does not tell us whether we will have additional brain benefits from being physically active long before age 80. But Casaletto, who is 36, said the study results encourage her to continue exercising.