Strong Support for the Brain Benefits of Aerobic Activity

Megan Brooks

September 19, 2011

September 19, 2011 — Any aerobic physical activity that raises the heart rate and increases the body's need for oxygen may reduce the risk for dementia and slow cognitive decline once it starts, according to a comprehensive literature review.

"We culled through all the scientific literature we could find on the subject of exercise and cognition, including animal studies and observational studies, reviewing over 1600 papers, with 130 bearing directly on this issue," J. Eric Ahlskog, MD, PhD, neurologist at the Mayo Clinic and professor of neurology at the Mayo Medical School, Rochester, Minnesota, said in a statement.

"We attempted to put together a balanced view of the subject," he said. "We concluded that you can make a very compelling argument for [aerobic] exercise as a disease-modifying strategy to prevent dementia and mild cognitive impairment, and for favorably modifying these processes once they have developed."

The research appears as a special article published in the September issue of Mayo Clinic Proceedings.

How Much Is Enough?

In comments to Medscape Medical News, Dr. Ahlskog noted that the amount of exercise needed to derive brain benefits has not been clearly defined. However, he said, "exercise sufficient to elevate the heart rate to about 60% of maximum, and done for about 150 minutes a week [divided], would be a good starting recommendation. This is similar to the American Heart Association recommendation."

Resistance exercise, such as weight lifting, also has beneficial effects, "but the literature on that is less extensive at this point in time," Dr. Ahlskog said.

"Normal aging is associated with brain shrinkage, and this appears to be primarily mediated by progressive loss of synapses and related neuronal connections (the 'neuropil')," the researcher explained.

As a clinical neurologist caring for older adults, Dr. Ahlskog said he's followed the "rapidly expanding" literature on the benefits of exercise on brain maintenance and integrity.

Based on the literature review, he said significant effects of aerobic exercise in humans have been well documented and include:

  • reduced subsequent risks for dementia and mild cognitive impairment,

  • improved scores on cognitive testing in both normal seniors and those with cognitive impairment,

  • better maintained brain connectivity, measured by functional magnetic resonance imaging, and

  • increased volumes of both brain cortex and hippocampus (a crucial memory area).

Animal studies have documented significant influences of exercise on:

  • learning and memory;

  • numerous indices of neuroplasticity, such as neuroplasticity-related transcription factors, hippocampal long-term potentiation, and dendrite and dendritic spine integrity;

  • elevated brain levels of neurotrophic factors, including brain-derived neurotrophic factor and glial-derived neurotrophic factor; and

  • hippocampal neurogenesis.

"Nice" Summary

Cyrus Raji, MD, PhD, from the University of Pittsburgh Medical Center Mercy Hospital, Pennsylvania, who was not involved in the research, said: "This paper nicely summarizes all of the latest evidence showing how regular physical activity can promote better brain health with aging and reduce the risk of Alzheimer's disease."

"While the majority of the evidence shows that aerobic physical activity is the best type of physical activity for this purpose, resistance training with weights may also be helpful," Dr. Raji added.

"What we need now are additional studies that examine if other lifestyle factors, such as diet, can produce a similar beneficial effect on the brain," he said.

Dr. Ahlskog and colleagues conclude, based on their research, that "exercise should not be overlooked as an important therapeutic strategy."

"Regular aerobic exercise of any type" should be encouraged, Dr. Ahlskog told Medscape Medical News.

He said it is important to note that not all exercise requires good legs and balance. "Gyms have a variety of exercise machines used in the sitting position, whereas swimming also is an excellent aerobic exercise."

"Not to be forgotten," he added, "are the routine things that we sometimes defer to others," such as raking leaves, shoveling snow, and cutting the grass with a nonsitting mower.

"Obviously, those with cardiopulmonary disease will need guidelines from their clinicians," Dr. Ahlskog emphasized.

Dr. Ahlskog and Dr. Raji have disclosed no relevant financial relationships.

Mayo Clin Proc. 2011;86:876-884. Abstract


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