ROCHESTER, Minn. — Regular physical exercise is the most powerful tool available to prevent Alzheimer's disease and improve brain function in those who already have it, according to the January issue of Mayo Clinic Health Letter. Exercise remains the best preventive therapy even though researchers, doctors, and drug and biotech companies worldwide are urgently seeking new therapies to prevent and treat Alzheimer's and other forms of dementia.
One Mayo Clinic study found that older adults who regularly engaged in moderate exercise five or six times a week reduced their risk of mild cognitive impairment by 32 percent compared with more sedentary people. Those who began exercising at midlife saw a 39 percent reduced risk of mild cognitive impairment. Mild cognitive impairment affects thinking and memory and is often a precursor to Alzheimer's. Numerous other studies have had similar results.
It's not clear how exercise protects the brain from Alzheimer's, but research indicates several possibilities, including:
Increased brain volume: Gray matter, where memory and other important functions occur, makes up the bulk of the brain. Gray matter typically decreases with age. Exercise appears to preserve gray matter.
An area of the gray matter called the hippocampus progressively deteriorates in people with Alzheimer's. In one study of older adults, significant enlargement of the hippocampus was seen in those who exercised moderately over the course of a year.
Improvement in levels of brain connections: Substances such as brain-derived neurotrophic factor are like fertilizer for the brain. Levels appear to rise with exercise and are lower in those with Alzheimer's disease.
Improved blood vessel health: Aging brain arteries are highly susceptible to narrowing and closure. Blood vessel closure can contribute to the development of cognitive impairment and Alzheimer's. Fitness helps prevent many conditions that contribute to damage and clogging of the blood vessels such as high blood pressure, diabetes and undesirable cholesterol levels and stress.
Moderate, regular exercise typically refers to about 150 minutes of exercise a week — or 30 minutes a day, five days a week. The exercise should increase the heart rate to about the level of a brisk walk. It's not known if exercising more or at more intense levels offers additional benefits in prevention of Alzheimer's.
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