How Much Exercise Is Too Much for the Brain?

Richard S. Isaacson, MD


November 09, 2018

Hi. I'm Dr. Richard Isaacson, director of the Alzheimer's Prevention Clinic at Weill Cornell Medicine and NewYork-Presbyterian. What is the most optimal dose of exercise, when should it best be begun, and can someone do too much exercise when it comes to brain health and Alzheimer's prevention?

Some really exciting research has recently been published. One paper was written by collaborators from the University of Miami Miller School of Medicine, Beth Israel Deaconess Medical Center, and Harvard Medical School, who came together to do a very broad review of the literature.[1] In that very nicely done paper, they showed that 52 hours was the optimal dose of exercise [associated with improved cognitive performance] over a 6-month period. Now, when you look at the numbers, that's about 2 hours of exercise per week. This included a mix of different [modes] of exercise, from aerobics to strength training, and a variety of different types.

In this study, exercise absolutely may have a positive impact on brain health. For the first time, we are starting to figure out a dose-related response. This is very interesting, but too much exercise may not be appropriate. Another study, called the DAPA trial, which was conducted in the United Kingdom, was a randomized study that enrolled people who had mild-to-moderate dementia.[2]

In that study, patients randomized to an active exercise regimen did not have any benefits, and in fact may have had slight cognitive worsening. First of all, what is the dose of exercise and when should it be begun? Is exercise better used for prevention rather than when someone has dementia? Could it even lead to worsening?

I think more studies are definitely needed, but the take-home point is that maybe a one-size-fits-all approach to exercise prescriptions is not optimal. For example, a person may need their exercise program tailored for them. Certain people who have excess body fat may need exercise interventions that reduce body fat and visceral fat to improve optimal metabolism. For example, as the belly size gets bigger, the memory center in the brain gets smaller. What is a way to try to reduce belly fat? Aerobic exercise on a regular basis and even high-intensity interval training are effective.

However, what if a person doesn't have adequate muscle mass? If a person is [participating in an] active aerobic exercise program but not doing any weight or resistance training, losing muscle mass has been associated with poorer brain outcomes. The take-home point here is that a person may need to have their body fat and muscle mass assessed, and then follow an individualized exercise program, whether it's two to three times a week of aerobic training and once or twice a week of weight and resistance training, or vice versa. This is an important consideration.

Additionally, [we may need to consider the] gender effects of exercise. There are a variety of studies demonstrating that maybe exercise should focus on body fat reduction in women but muscle strength in men.

We still have a long way to go, but I think, finally, we're starting to have some clarity in terms of exercise dose, type, and duration for the risk reduction and prevention of dementia and Alzheimer's disease.

For Medscape, I'm Dr Richard Isaacson.


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