Can physical exercise help prevent Alzheimer's disease? Here's what to know

In the next six years, 8.5 million Americans will have Alzheimer’s disease, and the rate is accelerating.

The collapse of mental capacity doesn’t happen all at once, like a stroke. It’s progressive, and once Alzheimer’s gets started, it keeps going and we haven’t yet found a way to stop it. For those in the early stages of Alzheimer’s, one-third will progress to a debilitating stage in about three years.

What does this mean? Increasingly, brain cells die, connections between brain cells are damaged and ineffective, memory declines along with thinking skills (cognition), and the brain shrinks. Alzheimer's robs us of our quality of life as it becomes increasingly more difficult, and ultimately impossible, to carry out everyday functions.

Thankfully, Alzheimer’s is a priority for medical scientists and progress is being made. This is good news, especially for those with a family history of Alzheimer’s because there is a hereditary link that increases risk. Regardless, with or without a hereditary link, there is much you can do to decrease risk, and increasingly, research supports daily exercise as a key element.

Can exercise help prevent Alzheimer's?

I have written on this topic several times in recent years as older folks constantly remind me that the worst part of aging is the fear of developing Alzheimer’s. In response, I ask: “Are you willing to engage in regular exercise because we know it helps reduce risk?”

Unfortunately, the vast majority are not willing to exercise, but they are quick to point out other things they are willing to do. These include so-called “mental gymnastics” like solving crossword puzzles, performing mental arithmetic, reading, playing mentally challenging games (chess, bridge, or computer games), etc.

These are all good activities, but they aren’t nearly as effective as regular exercise and I have pushed this concept repeatedly in this column. However, my purpose in this column is to expand the scope of how exercise helps the brain by reporting on the latest research.

In past columns, I have concentrated on what is known as “neurogenesis.” This means challenging the brain and stimulating it to make new brain cells (neurons) to compensate for neurons that are being destroyed and need to be replaced. When destruction outstrips replacement, neural capacity dwindles, and this is especially damaging in areas of the brain that control memory and cognition (the ability to think clearly).

What type of physical exercise can help prevent Alzheimer's?

Mental gymnastics as cited above are helpful in this regard but not nearly as helpful as exercise. Here’s why.

A seemingly simple physical activity like walking greatly challenges the brain. This is because the stimulus to walk is remarkably complex and a determination must be made by the brain as to which muscles should contract at a precisely coordinated moment and with how much force, and what other muscles must be blocked so as not to interfere.

When walking, this precise nerve activity requires instantaneous stimulation, going back and forth from one side of the brain to the other. This means with each step, back and forth, an incredible amount of brain activity is involved to allow smooth and flowing movement. Since walking is so helpful to the brain, imagine the potential benefits of more complex activities like dancing, Tai Chi, yoga, Pilates, etc.

In many ways, the effects of exercise on the brain are similar to challenging your muscles with resistance training to preserve muscle mass and strength. If neglected, muscles will atrophy (get smaller) and get weaker. Now we know that ignoring the brain also has deleterious functional effects over time.

How does exercise contribute to blood flow to the brain?

During exercise, blood flow is rerouted to the working muscles and away from other tissues like the liver and gut. Blood flow to the brain has always been assumed to be more or less constant regardless of exercise because the brain is so important, with potentially a slight increase due simply to the fact that the heart is pumping out much more blood. Now we know there is a greater increase in blood flow to the brain during exercise than previously thought, and this is believed to be another key factor explaining why exercise is so important to brain health.

Additional brain blood flow brings more oxygen to the brain which enhances “neurogenesis” (new nerve cell production) as explained above. When we are young, blood vessels are highly flexible, but with age, they stiffen. Also, young vessels are more compliant, dilating to increase diameter when there is a need for more blood flow, but this ability also declines with age. To help overcome the effects of aging on blood vessels, exercise triggers the release of nitric oxide from the walls of brain arteries. Nitric oxide dilates vessels, allowing increased blood flow and oxygen delivery.

Increased brain blood flow and greater oxygen delivery may also help break down the accumulation of beta-amyloid, the “nasty sticky protein” that forms in the brain, blocking communication among brain cells. In addition, exercise may also reduce inflammation and the buildup of free radicals which tend to accelerate the advancement of processes that cause damage to the body, including the brain.

All in all, evidence keeps growing in support of exercise as potentially the best way to combat Alzheimer’s. Unfortunately, the vast majority of Americans are sedentary and miss out on this benefit. If you fear Alzheimer’s, and especially if you have a family history, I strongly encourage you to slant the odds in your favor and exercise regularly. Your brain will thank you.

Reach Bryant Stamford, a professor of kinesiology and integrative physiology at Hanover College, at stamford@hanover.edu.

This article originally appeared on Louisville Courier Journal: Can physical exercise help prevent Alzheimer's disease? What to know