Regular walks may be a simple but effective way to protect thinking and memory, especially for people who have a gene that increases their risk of Alzheimer’s disease.
“Exercise is a great way to improve cognitive function — how we think and remember things — and in this study, the benefit seemed to be greater in APOE e4 carriers, though everyone benefited to some extent,” says the senior study author, Cindy Barha, PhD, an assistant professor of neuroscience at the University of Calgary and the Canada Research chair in neuroscience, brain health, and exercise.
How Do Genes Affect Alzheimer’s Risk?
Everyone carries some variant of the APOE (apolipoprotein E) gene, which plays a role in transporting cholesterol and other types of fat in the bloodstream. Breakdowns in this system are thought to contribute to the development of Alzheimer’s.
The APOE gene has three common variants:
- APOE e2 is the least common form of the gene, and is tied to lower Alzheimer’s risk. Estimates suggest about 8 percent of people carry this gene.
- APOE e3 is the most common form of the gene (carried by 78 percent of people) and doesn’t seem to affect risk.
- APOE e4 is carried by about 14 percent of people, and is linked to both increased Alzheimer’s risk and more severe disease.
For this analysis, Dr. Barha and her collaborators examined how walking affects Alzheimer’s risk for people with different variants of the APOE gene.
The study used data from nearly 3,000 Americans who participated in the Health, Aging, and Body Composition Study. Participants were between ages 70 and 79 at the beginning of the project, which examined risk factors for functional decline. Participants self-reported how often they walked by completing a standardized questionnaire.
After 10 years of follow-up, study authors found that, as expected, participants with the APOE e4 gene had steeper declines in cognitive performance than APOE e3 carriers. The results also suggested that people with APOE e2 had some protection against cognitive decline.
What was clear is that walking showed the strongest benefit for people with the APOE e4 variant.
“This study contributes to a growing body of literature on the benefit of exercise — in this case, self-reported walking was associated with less cognitive decline in APOE e4 carriers,” says Jessica Langbaum, PhD, the senior director of research strategy at Banner Alzheimer’s Institute and a codirector of the Alzheimer’s Prevention Initiative in Phoenix, Arizona. “This does not mean that walking isn’t beneficial for everyone,” she says, “just that it had the strongest effect in those with APOE e4.”
How Much Walking Do You Need?
The current analysis didn’t allow for an assessment of whether walking frequency, duration, or intensity made a difference, just that walking in and of itself was protective. But Barha did highlight previous research findings that elderly women participants who simply walked 10 blocks per day (or about one mile) had 13 percent lower odds of cognitive decline over a 6- to 8-year period.
Another study involving more than 74,000 adults found that between 3,800 and 9,800 steps every day may be enough to cut your risk of mental decline.
How Does Walking Lower Alzheimer’s Risk?
Although the study didn’t examine why walking helps the brain, Barha believes that exercise stimulates the production of a substance called brain-derived neurotrophic factor (BDNF) — a protein that supports nerve cell growth and survival.
“BDNF is like ‘fertilizer’ for your brain that naturally is produced especially when you are being physically active,” Barha says. “It helps brain cells survive, grow, and form stronger connections. This supports memory, learning, and mood, especially in the hippocampus, which is the brain’s memory center.”
Research also shows that exercise like walking improves blood flow to the brain, which can keep it operating smoothly.
Recognized Study Limitations
While results were based on a large number of participants and a long follow-up period of 10 years, Dr. Langbaum cautioned this was an observational study relying on self-reported amounts of walking, so the standard of evidence was lower than in a carefully controlled clinical study that might track walking data more accurately (with the use of Fitbits, for example).
Barha would like to see follow-up investigation focusing on quantifiable results that provide more precise data, such as how much walking is required to significantly slow cognitive decline.
She suggests that a trial involving a walking intervention that prescribes amount, duration, and intensity may be helpful.
Steps to Reduce Mental Decline
To get more steps into your day, Langbaum and Barha suggest the following:
- Get up regularly and walk throughout the day, especially if you spend large amounts of time sitting.
- Go for walks with others. Talking helps pass the time and stimulates your brain.
- When possible, walk instead of driving or taking public transportation.
- If you do have to drive, park at the back of the lot.
- Take the stairs when possible instead of an elevator or escalator.
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