Dear Doctors: What do you know about a study that says aerobics might be good for slowing down the progression of Alzheimer’s disease? I’ve read that being active helps your memory, but how would it affect an actual disease?
Dear Reader: You are referring to a study conducted by researchers in Great Britain that appeared in the journal Brain Research. And you are correct that it investigates the idea that regular physical activity can have a positive effect on the progression of Alzheimer’s disease. The study is part of a growing body of research into the role of physical activity in bolstering and preserving cognition. What makes it notable is that the findings offer clues to the question that you have posed, which is what causes the protective effect.
Although the word Alzheimer’s has become shorthand for dementia, it is actually a specific form of the brain disorder. Alzheimer’s disease is caused by the buildup in the brain of a sticky substance known as beta-amyloid protein. This protein collects into clumps known as plaques, which damage the neurons and disrupt neural pathways. An erosion of the myelin sheath, the fatty membrane that surrounds and protects neurons, may also play a role in the formation of toxic proteins. The first area to be affected is the hippocampus, which is the part of the brain that allows us to form memories. As the disease progresses, it gradually begins to affect the areas of the cerebral cortex that are associated with reasoning, logic, language and behavior.
Previous studies conducted in rodents have found that exercise can have a protective effect on the hippocampus. In this new study, researchers wanted to learn why. Their test subjects were 10 geriatric rats who were old enough for their brains to have begun the physical changes associated with Alzheimer’s disease. Half of the rats were put on an eight-week exercise program. This consisted of 30 minutes on an exercise wheel, five times per week. The other five, who served as the control group, remained sedentary.
When the researchers examined the rat brains at the end of the study, they found measurable differences in the two groups. The exercise group not only had a higher volume of normal neurons, but it also had lower amounts of the toxic proteins associated with Alzheimer’s disease. The exercise group also had lower amounts of a type of immune cell, which, when it malfunctions, is associated with age-related inflammation. The researchers concluded that regular physical activity may lead to beneficial changes in brain chemistry that reduce inflammation, slow the accumulation of toxic proteins and, thus, improve the survival of neurons. This has consequences not only for people living with Alzheimer’s disease, but also for all adults as they reach older age.
Although this was just one small study, the results are promising. The researchers are planning a human clinical trial. With an estimated 6.9 million people in the U.S. over the age of 65 now living with Alzheimer's disease, any advances toward managing the disease are very good news.
(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
