Lifestyle and the aging brain
There's a growing body of evidence that shows that we do have some control over protecting ourselves from signs of dementia and cognitive decline — and even the physical damages of Alzheimer's on the brain — through lifestyle.
A number of studies provide some fascinating evidence that highlights how lifestyle relates to one of the telltale signs of Alzheimer's: amyloid plaques in the brain. These plaques begin appearing years before any symptoms of dementia appear. The plaques and the damage they cause are easily identified in brain scans and autopsies, and when researchers looked at their relationship to controllable lifestyle factors, some intriguing and encouraging findings emerged.
Lifestyle and amyloid plaque formation
Different studies have looked at different lifestyle factors; the most obvious is a person's level of cognitive activity. One study started with a group of 65 older adults (average age of 76) with no signs of dementia or other cognitive impairment, and split these individuals into three groups based on their levels of cognitive activity (for example, reading, writing, or playing games).
Researchers then compared the levels of amyloid plaque in high, medium, and low cognitive activity groups to the plaque levels of 11 individuals with Alzheimer's disease and with a group of 10 younger adults (average age of 25). When the plaque level of the individuals who reported the lowest level of cognitive activity was compared to the levels of individuals with Alzheimer's disease, researchers found that the amount of plaque in the brain looked remarkably similar between the two groups, even though one group was not yet showing cognitive impairment. On the other hand, the level of plaque in older adults with the highest level of cognitive activity most resembled the much younger group.
Perhaps more surprising is the impact of physical activity on the formation of amyloid plaques. In an animal study where potentially confounding factors can be held consistent across all animals, researchers looked at the influence of physical exercise on amyloid plaque formation in mice. Comparing mice in cages that had a running wheel with those whose cages lacked the running wheel, they found that physically active mice with the running wheel showed between a 38% and 53% reduction in amyloid plaques in the brain areas of interest, compared to mice without the wheel. Those mice with running wheels were also found to be quicker learners.
Lifestyle, the impact of amyloid plaque, and Alzheimer's damage
Even more fascinating is research that compares individuals with similar levels of amyloid plaques or other Alzheimer's damage in their brains. Researchers examining autopsied brains have noted that while some brains that showed physical signs of Alzheimer's disease (such as amyloid plaques) came, not surprisingly, from individuals who had exhibited clinical symptoms of dementia, there were also some very similar-looking brains that came from individuals who showed no cognitive symptoms of Alzheimer's during their lives. When researchers compared what they knew about the lives of the individuals showing and not showing symptoms of dementia, they found that those who were not showing cognitive symptoms of dementia had been more active intellectually, socially, and physically throughout their adult lives.
While the brain benefits of cognitive, physical and social activity are now well-established, new lifestyle factors impacting brain health continue to be identified. Recently, researchers looked into how having a sense of purpose might affect cognitive abilities in individuals with similar amounts of amyloid plaque and other Alzheimer's damage in their brains. They compared those individuals who scored in the top 10% of a scale measuring purpose in life with individuals who scored in the bottom 10%. Not only did they find that individuals with the higher sense of purpose performed better on cognitive tasks than individuals in the low sense of purpose group with similar changes in their brains, they also found that the cognitive differences between these two groups increased as the amount of Alzheimer's pathology in the brain increased
The most common explanation for such findings is the theory of cognitive reserve, which suggests that as a result of lifestyle and other factors, “one individual may begin to express clinical features when synapses are depleted to a particular number, while an individual with more cognitive reserve may be able to operate effectively with the same number of synapses.” This difference has been attributed to an ability to maximize performance of brain networks or an ability to employ alternative cognitive strategies. And these abilities appear to be influenced by lifestyle!
Recent neuroscience research on lifestyle, Alzheimer's damage in the brain, and cognitive abilities gives us much encouraging evidence that the risk and rate of cognitive decline is not something that we have no control over, even once Alzheimer's damage has begun in the aging brain! And while the studies reviewed here are looking at the accumulated impact of lifestyle on the brain over a lifetime, there are a number of other studies conducted on older adults that show that even at later ages, increased cognitive and physical activity continues to offer cognitive benefits. The direct impact of lifestyle changes begun later in life may not always be visible when looking at indicators of Alzheimer's disease in the brain, but their benefits do show up when looking at performance on cognitive tests and other characteristics of the aging brain. While some risk factors for dementia are out of our control, we need to move away from a belief that dementia is inevitable and promote the idea that lifestyle changes can be made to reduce risk of dementia.
Roscoe Nicholson is a senior research associate at Mather LifeWays Institute on Aging.