by Gabe Mirkin, M.D.
Three new studies help us understand the many good things that exercise does for your brain. The first study, from the University of Maryland, shows that a regular exercise program alters blood flow to the brain to improve mental function in older people who suffer from mild cognitive impairment that often precedes dementia (Journal of Alzheimer’s Disease, Feb 1, 2019;67(2):671-684). The second study, from Columbia University, shows that exercise can improve thinking skills in people of all ages (Neurology, January 30, 2019). The third study, from McMaster University, shows that exercise-induced muscle changes can help to boost mood in older adults (American Journal of Physiology–Cell Physiology, Jan 31, 2019).
Exercise Improves Brain Function in People with Early Dementia
Early dementia is called “mild cognitive impairment” and people with early dementia have increased blood flow to their brains that is associated with inflammation. In the study from the University of Maryland, people with early dementia benefitted from a 12-week program of exercise that reduced the blood flow from inflammation (Journal of Alzheimer’s Disease, Feb 1, 2019;67(2):671-684). Their cognitive test scores were also significantly improved after the 12-week exercise program.
Earlier studies have suggested that dementia may be caused by an overactive immune system (Neurology, November 28, 2017; 89 (22)). Your immune system is supposed to protect you from invading germs, but when it doesn’t shut down after an infection is controlled, it can attack parts of your own body in the same way that it attacks the germs. Your immune system responds to germs by increasing blood flow to bring immune proteins and cells to the part of the body that is being invaded. In the same way, when your immune system stays active all the time (inflammation), it can markedly increase blood flow to the brain to bring in white blood cells and chemicals called cytokines, which can attack and damage your brain.
In this new study, a regular exercise program reduced the increased inflammation-induced blood flow to the specific brain regions that are known to be involved in the development of Alzheimer’s disease, including the insula (perception, motor control, self-awareness, cognitive functioning), the anterior cingulate cortex (decision making, anticipation, impulse control and emotion) and the inferior frontal gyrus (language processing and speech). Interestingly, the control group of healthy adults who did not have “mild cognitive impairment” benefitted from exercise by having an increased blood flow to the frontal parts of their brains and they also improved their cognitive test scores significantly after the 12-week exercise program. The same authors have previously shown that exercise improves brain blood flow and mental function in healthy people.
Exercise Improves Mental Function at All Ages
In the study from Columbia University, the researchers followed 132 healthy non-demented people, ages 20 to 67, who had below average fitness levels and did not exercise (Neurology, January 30, 2019). They were assigned randomly to one of four groups, to wear heart rate monitors in an exercise program of four sessions per week for six months. Three of the groups did aerobic exercise: walking on a treadmill, cycling on a stationary bike or using an elliptical machine. The fourth group served as the control group, doing a non-aerobic program of stretching and minimal core-strengthening movements. The three aerobic-exercise groups worked up to training at a demanding 75 percent of their maximum heart rates, while the non-aerobic group did not raise their heart rates.
All four groups were tested for thinking and memorizing three times: at the start of the study, at three months and six months. The three groups that did aerobic exercise gained in “executive function,” while the non-aerobic group showed no changes. Executive function evaluates a person’s ability to act appropriately, pay attention to presented facts and achieve specific goals. Interestingly, the improvement in thinking skills was greatest in the older participants in the three aerobic groups. MRI brain scans at the start and end of the study also showed that the aerobic exercisers had an increase in the thickness of the outer layer of the left frontal area of the brain (Decreased brain function is associated with loss of brain size). They also found that participants who had APOE4, a genetic marker of high risk for Alzheimer’s disease, had reduced gains in problem solving.
Exercise May Help Fight Depression in Older Adults
As muscles become stronger through regular exercise, they release transcription factors that can improve your mood and help to make you feel good. A regular exercise program helps your body to process tryptophan, a mood-enhancing chemical closely related to serotonin. Depressed people often have low blood levels of serotonin, and exercise may increase activity of the enzyme KAT from exercising muscles that converts tryptophan to serotonin to help make you feel good.
In the study from McMaster University, a group of healthy men who were 65 or older and not depressed did 12 weeks of leg and shoulder presses and high-intensity stationary bicycle interval training. Their enzyme KAT levels increased significantly (American Journal of Physiology–Cell Physiology, Jan 31, 2019). An earlier study showed that exercise also causes muscles to release large amounts of cathepsin B that is associated with improved memory (Cell Metab, Aug 9, 2016;24(2):332-40). Those who had the highest improvement in fitness also had the highest blood levels of cathepsin B and the greatest improvement in memory test scores.
If you exercise regularly, these three new studies give you more reasons to be proud. Your exercise can help you to prolong your life, prevent certain diseases and protect yourself from dementia and depression. If you are not yet a regular exerciser, check with your doctor so you can start an exercise program.