The Globe and Mail

Here’s one more reason to go for a walk or go jogging today: Doing so might help fight Alzheimer’s, especially if you’re predisposed to the disease, according to a new study published in Archives of Neurology.

Previous studies have examined the effect exercise has on the disease, with mixed results. Some found exercise to be very beneficial whereas others found its impact on the disease to be marginal at best. In an attempt to better understand the effects, researchers at Washington University decided to study people with a particular gene variant called APOE e4. Everyone carries the APOE gene, but those with this particular variant are 15 times more likely to develop Alzheimer’s than those who do not carry it.

The scientists looked at 201 adults aged 45 to 88. Some had a family history of Alzheimer’s, but at the time of the study all of them were cognitively normal – even the 56 volunteers who were found to carry the APOE e4 gene variant, according to Denise Head, an associate professor of psychology who led the study.

Brain scans were used to discover the level of amyloid plaques, a hallmark of Alzheimer’s, on the volunteers’ brains. Those volunteers also provided detailed questionnaires regarding their exercise habits during the past decade.

Taken as a whole, exercise did little to mitigate the accumulation of plaque for the entire group. However, when researchers looked only at those who carried the e4 variant, the results were remarkable.

People who carried the gene variant and who reported walking or jogging for at least 30 minutes five times a week were found to have the same level of plaque buildup as people who were not carriers of e4. In other words, exercise seemed to counteract the increased risks posed by the e4 variant.

“It could be particularly beneficial for you to exercise if you have the at-risk gene,” Prof.. Head said. (The only way to know if you have the gene variant is to get tested for it.)

Prof. Head said the study provides reason to be “cautiously optimistic” regarding the link between exercise and Alzheimer’s. “We have a small sample, we didn’t follow these people over time. There are a lot of limitations to this story,” she said.

But it’s still a good idea to lead an active lifestyle.

“There’s a lot of reasons to be aerobically active,” said Prof. Head. “This study suggests this may be one more.”

Why exercise is good for the brain:

The effect of exercise on the brain has become a hot topic in research circles. Many recent studies have revealed a link between active living and improved memory.

How can exercise improve memory? Irish scientists may have come up with the answer in a study published last fall in the journal Physiology & Behavior. Male college students took a memory test and then one half of the volunteers rode an exercise bike until they were exhausted, while the other half sat idle. Both groups took the test again. The bike riders did much better, while those who rested showed no improvement. Those who exercised were found to have increased levels of a protein called brain-derived neurotrophic factor, which promotes the health of nerve cells.

In a 2010 study published in the Proceedings of the National Academy of Sciences, researchers from the University of Cambridge and the National Institute on Aging in Baltimore, Md., found that mice that had access to a running wheel performed nearly twice as well on memory tests than mice with no access. Moreover, the running mice were found to have grown an average of 6,000 new brain cells per cubic millimetre in the hippocampus, which researchers hypothesized was due to the fact exercise increases blood flow to the brain.

In another study of running mice, researchers at the University of South Carolina discovered that mice that had run on a treadmill every day for eight weeks developed new mitochondria in their brain cells. Mitochondria, which help power cellular activity, may help prevent against neurodegenerative diseases such as Parkinson’s and Alzheimer’s, researchers said shortly after the study was published in the Journal of Applied Physiology in August 2011.