Keeping your mind and muscles from going to flab in middle age could protect you against Alzheimer's disease as you grow old.
Researchers say people who maintain intellectual and physical activity as adults are far less prone to the degenerative brain disorder late in life. Although some of the effects may be due to cardiovascular fitness, most of the benefits of an active life likely involves preserving brain power, says a the study in the March 13 issue of the Proceedings of the National Academy of Sciences.
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"The brain is like every other organ in the body: It ages better when it's used," says lead study author Dr Robert Friedland, a neurologist at Case Western Reserve University in Cleveland. "When you're busy learning, when the brain is involved in learning, the health and size and connectivity of neurons is enhanced."
Friedland's team measured changes in 26 activity levels in 193 patients with likely or possible Alzheimer's and 358 healthy people. Some activities were physical, like exercise and gardening; some were passive, like television viewing and going to church; others were intellectual, including reading and writing letters.
In addition to the variety of activities people pursued with age, the researchers also were interested in how intensely subjects stayed involved between ages 20 and 60.
Compared with Alzheimer's patients, people with healthy brains had been involved in a broader variety of activities during adulthood, the researchers say. Those whose activity levels fell below the average had nearly a four-fold increase in the risk of the disease, even after accounting for other Alzheimer's risk factors like age and education level.
What's more, people who spent more time pursuing the 26 activities as they got older appeared to gain significant protection from brain changes linked to Alzheimer's.
In fact, Alzheimer's patients, or their caretakers, reporting doing less of every activity than healthy subjects except one, television watching, says Friedland. "TV represents an activity which is often not intellectual, and is not physical except changing the channels."
Of course, experts say, it's impossible to know whether the patients who had Alzheimer's developed the disorder because they didn't exercise their brain, or, conversely, whether early symptoms of the disease kept them from fully enjoying their minds.
"It's hard to know what that means," says Kathy Riley, an Alzheimer's researcher at the University of Kentucky in Lexington, who is familiar with the latest study. "Is it that they're cutting back because Alzheimer's is already affecting them, or does cutting back on their intellectual activity make them more susceptible to the symptoms" of the disease?
Riley and her colleagues have been conducting a long-term study of dementia in nuns. Among other things, their study has found that sisters who had language problems as children were more likely to develop Alzheimer's disease as seniors.
While the link between intellectual activity and Alzheimer's is becoming clearer, the link to exercise is somewhat murkier, say the experts. Cardiovascular fitness could help avoid tiny vessel breaks in the brain, essentially mini-strokes that kill off brain cells.
"We've got data that show that if you have Alzheimer's pathology and very small strokes, the two together make [dementia] worse," Riley says.
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