The new study, published Wednesday in the online issue of Neurology, is unique because Buchman was able to analyze the actual brains of study participants. The findings are a "great thank you" to the participants who agreed to donate their brains for research after death, he says.
The study looked at 454 older adults who were 70 or older when the research began. Of those adults, 191 had behavioral signs of dementia and 263 did not. All were given thinking and memory tests every year for 20 years.
In the last years of research before death, each participant wore an activity monitor called an accelerometer, similar to a Fitbit, which measured physical activity around the clock — everything from small movements such as walking around the house to more vigorous movements like exercise routines. Researchers collected and evaluated 10 days of movement data for each participant and calculated an average daily activity score.
The findings show that higher levels of daily movement were linked to better thinking and memory skills, as measured by the yearly cognitive tests. And when Buchman analyzed brain tissue under a microscope, this finding turned out to be the case even for individuals with at least three signs of Alzheimer's disease, such as amyloid plaques and neurofibrillary tangles. Even though these individuals might have been diagnosed with Alzheimer's, 30 percent of them had "normal" cognition at death, says Buchman.
Why one person shows signs of dementia and another, who has similar degenerative changes in the brain, does not, is a mystery. But Buchman says the new findings suggest that physical activity may be protective, even amidst developing Alzheimer's. It sort of masks the symptoms, he says, and is an "empowering finding" suggesting you can have some control over your brain health even if you don't have control over developing Alzheimer's.
"It's almost as if the physical activity was helping the brain to bypass the physical damage," says Dr. Tim Church, a preventive medicine specialist with Pennington Biomedical Research Center at Louisiana State University who was not involved in the research. "It appears that physical activity was critical to creating a reserve that protects against those physical damages."
And, while intense activity and exercise is highly beneficial, even light activity can make a difference, says Buchman. "As long as you have some activity and you're moving, whether you're chopping onions, typing, sweeping the floor or even running," you can reduce your risk of cognitive decline.
The findings are impressive, says research scientist Carl Cotman, director of the Institute for Brain Aging and Dementia at the University of California, Irvine, showing that physical activity may "offset the ill effects of brain degeneration." He adds that lifestyle interventions such as an increase in physical activity and movement can be powerful even in the presence of disease. Cotman was not involved in the research.
But exactly how the protective effect may work is unclear. Buchman says the current findings are a "great start" but he hopes to look more closely at participant's brains to measure different proteins and try to identify which ones might link physical activity to better cognition.
There are some caveats to the study. The findings do not show clear cause and effect. Study participants with dementia had significantly lower indications of movement compared to those without dementia. It may be possible that as people lose memory and thinking skills, they also reduce their physical activity.
And the study did not have data on how active participants were over the course of their lives. It could be that older adults who moved more were also lifelong exercisers so it's not known if physical activity in early life may have played a role.