Published on: January 11, 2012
by Nicole Ostrow for Bloomberg Businessweek:
People who are genetically susceptible to developing Alzheimer’s disease may be able to reduce their risk with exercise, a study found.
Carriers of the Alzheimer’s gene APOE-4 who regularly exercised over a decade were five to 10 times less likely to have brain plaques linked to the disease than those with the gene who weren’t physically active, said John C. Morris, senior author of the study published today in Archives of Neurology.
About 5.4 million Americans have Alzheimer’s and, by 2050, that number is expected to grow to as many as 16 million, according to the Alzheimer’s Association. Between 15 and 20 percent of the general population carry the APOE-4 gene, Morris said. While the study shows that those who exercised had fewer amyloid plaques in the brain, the signature markers of the disease, more follow up is needed to see if exercise actually delayed or blocked symptoms, he said.
“It’s not proof that exercise is protective, but it’s a very strong association and it gives biologic credence that staying physically active may help us protect against Alzheimer’s disease,” said Morris, director of the Knight Alzheimer’s Disease Research Center and a professor of neurology at Washington University in St. Louis, Missouri, in a Jan. 6 telephone interview.
Alzheimer’s destroys brain cells, making it difficult for patients to think, remember and function. Markers of brain cell death include amyloid plaques and tangles, Morris said. That process can begin in the brain 10 to 20 years before symptoms occur. The patients need to be followed for years to determine if they actually become symptomatic, he said.
The study involved 201 people ages 45 to 88 years without symptoms of Alzheimer’s disease who filled out questionnaires on their physical activity during the past ten years. The patients were also tested to see if they carried the APOE-4 gene. The researchers then used spinal fluid tests or brain images to see if the patients had amyloid deposits in their brain.
About one-third of the study participants carried the APOE- 4 gene, Morris said. Those who engaged in brisk walking or jogging at least 30 minutes a day, five days a week benefited from the physical activity, he said.
Those without the gene and exercise didn’t have the same results.
Researchers are unsure how exercise reduces amyloid in the brain. Physical activity helps diminish other risk factors in mid life that are associated with an increased risk of Alzheimer’s disease later, including heart disease, diabetes, obesity and high blood pressure, Morris said. Exercise may help promote brain health.
“Just how exercise does it, we don’t know,” Morris said. “Whatever we can do to prolong the eventual appearance of Alzheimer’s disease symptoms or eventually prevent the onset of Alzheimer’s disease symptoms will be very important for people who know they are at risk for developing Alzheimer’s disease.”
The number of people worldwide with the condition is expected to swell to 115 million by 2050 and there are no effective treatments. Existing medications have only been found to ease symptoms temporarily.
Studies on Alzheimer’s disease and exercise have shown mixed results.
An August 2009 study in the Journal of the American Medical Association showed that those who adhered most closely to a Mediterranean diet rich in fish, fruits and vegetables and were the most physically active had about a 60 percent lower risk of developing Alzheimer’s disease compared with those who didn’t follow the diet and exercise.
In June 2010, a panel advising the National Institutes of Health said that an analysis of research showed that exercise or following the Mediterranean diet may not slow memory loss or lower a person’s chance of developing the disease.
Heather Snyder, senior associate director of medical and scientific relations at the Alzheimer’s Association in Chicago, said in a telephone interview today that today’s study starts to bring together a lot of different areas of Alzheimer’s research, but more trials are needed to show whether exercise can delay or prevent the onset of the disease.
“They’re really looking at a snapshot in time,” she said. “The ultimate study would be to have a very large population that was followed over a long period of time, similar to what we’ve seen in heart health.”
Even though more research is needed, the Alzheimer’s Association suggests people stay physically and mentally active, socially engaged and eat a well-balanced diet, including green leafy vegetables, to maintain brain health, Snyder said.
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