By JOHN OWEN
“Exercise is the most important thing you can do to maintain your cognitive health.”
—Dr. Sharon Inouye, Director of Harvard University Medical School/Aging Brain Center
Identical twins we’ll call Sarah and Susan posed a real mystery to researchers in England a few years ago. When exhaustive biometric measurements were taken, the sisters were discovered to be exactly the same in all respects. During their years in the study, however, Susan’s brain became smaller and unhealthy compared to Sarah’s. Susan’s smaller brain led, unsurprisingly, to reduced cognition and function, whereas Sarah’s larger brain continued to function normally. Susan also suffered from weakness.
In addition to their examination of physiological and cardiovascular risk factors such as cholesterol and blood pressure, researchers examined small details of the twins’ lives. The twins grew up in the same house, had similar diets, and attended the same schools. Both married at about the same age and had remarkably similar husbands and families. Their careers were also similar. Neither was subject to more stress in their life, and neither was exposed to unique environmental hazards.
When they went back to reexamine their data in more detail, the researchers found only one small difference—Sarah had stronger leg muscles. There, at last, they found their answer: Sarah walked a lot and Susan was sedentary. That small detail was the deciding factor in their vastly different mental conditions as they aged.
The researchers conducting the study know a lot about twins. They are a part of the Twin Project conducted by the Department of Twin Research & Genetic Epidemiology at King’s College, London. The project has, since 1992, studied more than 20,000 twins. Its mission, as stated on its website, is to “investigate the genetic and environmental basis of complex diseases and conditions to understand how genetic variation relates to human health.” The researchers have amassed a remarkable amount of genetic data.
How, you might ask, does leg strength relate to cognitive health as people age? According to Claire Steves, Ph.D., a geriatrician who heads the Twin Research & Genetic Epidemiology department, brain imaging was done at the beginning of the study. Years later, when imaging was done again, Sarah, the twin with the stronger legs had more gray matter and more white matter with less empty space in the skull. “Looking at the X-rays, you don’t need to be a neuroscientist to see that the empty spaces are much smaller in the stronger twin than in the weaker twin,” Dr. Steves says. And most people will agree that you don’t have to be a neuroscientist to know that having empty spaces in your brain is a bad thing!
Why was Sarah’s brain larger? Because, when you walk, your legs pump blood to your brain delivering more oxygen and nutrients to feed your brain, helping it to function and thrive. The legs are sometimes called “the muscle pump” or “the second heart” because they have a system of muscles, veins, and one-way valves in the calf and foot that work together to push blood back up to the heart and lungs. The vein valves open and close with each muscle contraction to prevent the backflow of blood.
We all lose muscle mass and strength beginning around the age of 30 and progressing at approximately three to eight percent per decade. The rate of decline is even higher after the age of 60. This is why we all need exercise—to slow or prevent this decline. In the case of the twins, Sarah’s walking protected her from at least some of these problems since she didn’t exhibit any symptoms of frailty and weakness. Susan’s lack of walking, on the other hand, resulted in muscle wasting (sarcopenia), which contributes to frailty and falls. The U.S. Centers for Disease Control and Prevention reports that more than 25 percent of all Americans over the age of 65 will fall each year.
By her practice of walking, Sarah was not only supplying more blood, oxygen, and nutrients to the brain, but the moving blood caused profound changes in her body chemistry through a magical process called mechanotransduction. Don’t let that word scare you. If you can say mechanic transmission, it’s almost the same thing. Let’s just call it transduction.
When blood is flowing through your arteries, the blood cells create friction with the lining of that vessel, called the endothelium. The cells forming the endothelium respond to this friction by producing chemicals. It’s kind of like rubbing something to create static electricity, which is another kind of transduction.
What kinds of chemicals? Many helpful substances such as antioxidants, anti-inflammatories, and anticoagulants. Walking also causes the muscles to produce several myokines, which are small messenger proteins that can help reduce the chemicals (tau and amyloid beta) that cause Alzheimer’s disease and Parkinson’s disease. Marc Milstein, PhD, author of The Age Proof Brain, says, “Simply walking is really important for your brain health and people who walk 30 minutes a day can lower their risk of dementia by about 60 percent.”
According to Walking for Health, published by the Harvard Medical School, you can lower your blood pressure, fight heart disease, reduce the risk for diabetes, relieve depression, improve memory, and add healthy years to your life just by walking! Harvard advertises the booklet as, “The simple cure for the biggest health problem in America.”
Does this mean that you can delay or even escape cognitive decline if you just keep walking? Well yes, it probably does. It depends on your current health and age, any other medical conditions you may have, and how faithfully you adhere to the requirements of your walking routine. There are some requirements, of course. You should walk at least 150 minutes a week at a brisk pace of about 100 steps per minute. That’s about the tempo of Stayin’ Alive by the BeeGees, Another One Bites the Dust by Queen, or Walking After Midnight by Garth Brooks. You can walk 30 minutes a day for five days or 15, 10-minute sessions scattered throughout the week. If you really want to delay the cognitive effects of aging and stay mentally sharp, just do like Aerosmith and Walk This Way!
John Owen transitioned from life as a graphic artist/website designer to a biomedical executive at the age of 61. After 20 years in the biomedical business, he now uses his knowledge of medicine and physiology to write about successful, vibrant aging. This is excerpted from his forthcoming book on super-agers.
More articles on the cognitive benefits of exercise:
Your Brain is like a Reservoir. Replenish it with Healthy Activity.