02:13 - Source: CNN
WATCH: Nearly 40% of dementia cases can be prevented with one small health change
CNN  — 

Living a healthy lifestyle with a focus on a nutritious diet, regular exercise, minimum alcohol consumption and other healthy habits can help keep your brain sharp into old age, doctors say.

But what if your brain already has signs of beta amyloid or tau — two of the hallmark signs of Alzheimer’s and other brain pathologies? Will a healthy lifestyle still protect you from cognitive decline?

The answer is yes, according to observational research that examined the brains of 586 people during autopsies and compared the findings with up to 24 years of data on their lifestyles.

“We found that the lifestyle-cognition association was independent of Alzheimer’s disease pathology burden, suggesting that (a healthy) lifestyle may provide cognitive benefits even for people who have begun to accumulate dementia-related pathologies in their brains,” said lead author Dr. Klodian Dhana, an assistant professor of geriatrics and palliative medicine at the Rush Institute for Healthy Aging in Chicago, via email.

In other words, the study found the presence of Alzheimer’s or another neurological disorder “didn’t seem to matter — the lifestyle changes provided the brain resilience against some of the most common causes of dementia,” said Dr. Richard Isaacson, director of research at the Institute for Neurodegenerative Diseases in Florida.

“It’s like a video game where you are shooting monsters,” said Isaacson, who wasn’t involved in the study. “The gun —the lifestyle changes — was able to defeat the ghosts, ghouls, goblins, vampires and zombies.”

Five healthy habits were tracked

For the study, autopsies were performed on 586 people living in retirement communities, senior housing and individual residences in the Chicago area who had participated in the Rush Memory and Aging Project between 1997 and 2022. The participants, who lived to an average age of 91, underwent regular cognitive and physical testing and filled out annual questionnaires on their lifestyles for over two decades before they died.

People in the study were categorized as living a low-risk or healthy lifestyle if they scored top marks in five different categories: they did not smoke; they did moderate to vigorous exercise for at least 150 minutes a week; they kept their alcohol consumption to about one drink a day for women and two for men; and they regularly stimulated their brain by reading, visiting museums, and playing games like cards, checkers, crosswords or puzzles.

The fifth category measured how well they followed the Mediterranean-DASH Diet Intervention for Neurodegenerative Delay or MIND diet. Developed in 2015 by researchers at Rush University in Chicago, the MIND diet incorporates much of the plant-based Mediterranean diet, which focuses on fruits, vegetables, whole grains, beans, seeds, nuts and a lot of extra-virgin olive oil. Red meat and sweets are eaten rarely, but fish, which are packed with good-for-you omega-3 fatty acids, are a staple.

The MIND diet also assimilates elements of the Dietary Approaches to Stop Hypertension (or DASH) diet. The DASH diet focuses on lowering blood pressure and cholesterol, which can lead to heart attacks, strokes and constriction of small blood vessels that can lead to dementia. The standard DASH diet limits salt to 2,300 milligrams a day, less than a teaspoon of table salt.

Kobus Louw/E+/Getty Images
Eating a plant-based, low-salt diet is good for the brain, experts say.

Use of autopsies was unique

The study team then compared lifestyle data to various measures of pathology in the brain, including levels of beta-amyloid, tau tangles, and signs of vascular brain damage, or injury to the small blood vessels in the brain that occur from high blood pressure, heart disease and diabetes.

Not everyone who has signs of Alzheimer’s or vascular dementia goes on to develop cognitive issues, but many do.

Researchers also measured markers of three other brain diseases, including drug-resistant epilepsy, frontotemporal degeneration and Lewy body dementia, a neurological disorder that can create problems with behavior, mood, movement and cognition.

The research, published Monday in the journal JAMA Neurology, “is one of the first to harness brain pathology” from autopsies to investigate the link between modifiable risk factors and cognitive decline, professors Yue Leng and Dr. Kristine Yaffe wrote in an accompanying editorial.

Yaffe, who was not involved in the study, is a professor of psychiatry, neurology and epidemiology at the University of California, San Francisco Weill Institute for Neurosciences. Leng, who was also not involved in the study, is an associate professor of psychiatry at the same institution.

For every 1-point increase in the healthy lifestyle score used in the study, there were 0.120 units less beta-amyloid load in the brain, and a 0.22 standardized unit higher score in cognitive performance, which was measured by a test of about 30 items that examined attention, memory, language and visuospatial skills.

The cognitive benefits remained regardless of the existence of any of the five types of neurological conditions. In fact, “a higher healthy lifestyle score was associated with better cognition even after accounting for the combined burden of brain pathologies,” according to Yaffe and Leng.

More than 88% of a person’s global cognition score was a “direct association of lifestyle,” they said, leaving slightly less than 12% affected by the presence of beta-amyloid.

As an observational study, it’s not possible to prove a direct cause and effect, Yaffe and Leng said. However the study is “an important step” in understanding the ways people can modify their lives to reduce the risk of Alzheimer’s disease and other types of dementia.