THE WASHINGTON POST: The midlife habits that could make or break your brain health long-term

Neuroscientist Miia Kivipelto’s life’s work has been about preventing dementia. Now, at 52, she has begun thinking more about her own vulnerability.

“Midlife is the time,” said Kivipelto, a neuroscientist who recently joined the Yale School of Nursing as the inaugural director of its Center for Aging Well in New Haven, Connecticut. “It’s the last best chance to lower risk.”

The idea that dementia prevention may hinge on what people do in their mid-30s to their 60s is rapidly reshaping the field. Scientists increasingly believe the disease is driven not only by changes in the aging brain, but also by years of metabolic stress, inflammation and vascular damage accumulating across the body. Many researchers now think the biological process that leads to dementia begins 15 to 20 years before the first memory problems emerge. By the time symptoms become noticeable, the disease likely will already be well established.

Neuroscientists now see midlife as a critical window when the brain becomes especially vulnerable to aging - but also more responsive to intervention.

The implications are profound: The ordinary habits of middle age may matter far more than scientists once realized, and cognitive decline may not be inevitable.

Last year, a large study in JAMA Network Open found that people who remained physically active during midlife had a 40 to 45 percent lower risk of dementia later in life. A meta-analysis of more than 3 million people published in April in PLOS One found that the greatest reductions in dementia risk came from how people behaved in midlife and were associated with seven to eight hours of sleep, at least 150 minutes of aerobic activity a week, and fewer than eight sedentary hours a day.

Taken together, the findings suggest a new pathway for addressing a growing societal problem. More than 57 million people worldwide are living with dementia, and researchers predict that number will nearly triple to more than 150 million by 2050, according to estimates published in the fulltext. Scientists now estimate that roughly 45 percent of cases could potentially be delayed or prevented through changes to modifiable risk factors.

“The younger you are, the greater the bang for the buck in terms of these behaviors and lowering your risk,” said Akinkunle Oye-Somefun, a research associate at York University in Toronto and a co-author of the PLOS One study.

Researchers stress, however, that the message is not that prevention ends after people turn 70. While the evidence suggests the greatest benefits may come from changes made in midlife, studies also indicate that exercise, sleep, social engagement and other healthy habits can help support brain health well into a person’s 70s and 80s.

Brain changes in midlife

For much of the 20th century, scientists thought brain development followed a relatively fixed arc: rapid growth in childhood, stability in adulthood and gradual decline with age. The adult brain was seen as largely static, with limited ability to reorganize itself later in life.

But in a 2024 Stanford University study, researchers found large shifts in proteins linked to metabolism, immune function and cardiovascular health clustered around the mid-40s and early 60s. Because these systems help regulate blood flow, inflammation and energy supply to the brain, changes in them can also influence cognitive function and overall brain health as people age. In November, a different research team found four pivot points in brain changes including at ages 32 and 66.

That means the last big bursts of brain growth may end as middle age closes, researchers say, and that habits like poor sleep, inactivity and chronic stress may already be taking a toll.

Ahmad Hariri, a professor of psychology and neuroscience at Duke University, said that idea really hit home in the past year with the “overwhelmingly disappointing” results of several treatments for Alzheimer’s in older adults, including GLP-1s and some drugs targeting the amyloids, or plaques, that accumulate in the brain.

“It seems if you wait until later life to intervene it’s too late, the damage that has been done is really irreversible,” he said. “That kind of naturally shifts the timeline back to midlife.”

Hariri believes future brain scans and blood tests will identify people whose brains are aging unusually quickly. The goal, he said, is not simply to predict decline but to change course while there is still time.

For example, if someone who is 54 - Hariri’s age - learns their brain is aging faster than most people their age, it could serve as a powerful wake-up call, he said.

“By sharing with people that their biological aging is in the 80th or 90th percentile,” he said, ”that could then be a strong motivation for that patient to dig in and commit to these lifestyle changes.”

The big three: Diet, exercise, sleep

So what could a prescription for healthier brain aging look like? Three factors - diet, exercise and sleep - have arguably drawn the most attention in recent years.

Last year, a 30-year-study involving 100,000 people found that adults who stick to diets rich in plant-based foods and eat fewer ultra-processed foods during their 40s, 50s, and 60s not only have a higher likelihood of reaching their 70th birthday free of major chronic disease - but also still performing normally on cognitive tests and without depression.

Exercise, brain-imaging research suggests, may help preserve regions involved in memory and executive function, slowing some forms of age-related shrinkage. Increasingly, scientists describe exercise not simply as healthy behavior, but as a form of neurological maintenance.

Scientists believe sleep in midlife may shape how effectively the brain clears away waste proteins associated with Alzheimer’s disease. During deep sleep, the brain undergoes a kind of nightly cleaning process. Chronic sleep disruption, researchers suspect, may impair that process years before cognitive symptoms emerge.

Yet those physical factors are only only part of the equation.

Challenge and novelty

Scientists increasingly believe the brain flourishes when it is pushed to learn, adapt and explore new experiences. The finding aligns with the theory of cognitive reserve - the idea that mental stimulation helps the brain build resilience against age-related decline by strengthening alternative neural connections.

Learning a language, mastering an instrument or taking up an unfamiliar hobby - especially one that’s creative - may help build resilience over decades. In fact, a study published in the March issue of Neurology found people who had the highest levels of what researchers called “cognitive enrichment” - engaging in activities like reading and writing or visiting museums - developed Alzheimer’s five years later than those with lower scores.

This means the brain may also be less resilient when people age alone. Conversations, friendships and group activities place constant demands on memory, attention, emotional processing and language - a kind of full-brain exercise that cannot happen in isolation.

Perhaps most encouraging, many of the factors linked to dementia can be lessened. A landmark 2024 report by the Lancet Commission, a major international panel of scientists and public health experts that reviewed evidence on dementia prevention, treatment and care, identified 14 modifiable risk factors across a person’s life and highlighted 10 as important to midlife.

Some factors pose a larger risk than others. The Lancet Commission estimated that high LDL cholesterol and hearing loss - which forces the brain to work harder to decode sound, and can lead to social withdrawal and isolation - each account for roughly 7 percent of dementia cases worldwide, while depression and traumatic brain injury each account for about 3 percent. Physical inactivity, diabetes, smoking and hypertension were each linked to about 2 percent of cases, with obesity and excessive alcohol use contributing an estimated 1 percent.

A scientist’s own risk

Kivipelto first became interested in dementia research after watching her grandmother experience it. As a teenager, she noticed her grandmother - who lived with the family - had begun hiding objects and forgetting things.

When Kivipelto entered the field about 30 years ago, she said, few researchers believed health factors elsewhere in the body could influence dementia risk. One of her earliest papers, published in 2001 the BMJ, formerly the British Medical Journal, linked high blood pressure and cholesterol to Alzheimer’s risk later in life. Multiple journals initially rejected it.

“There was a lot of skepticism at that time,” she said. But she was right.

Kivipelto became widely known for leading the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability, or FINGER trial. It was one of the first large studies to show that a combination of exercise, healthier diet, cognitive training and cardiovascular monitoring could help preserve cognitive function in older adults at elevated risk for dementia.

Now, she tries to apply the research to her own life. She stays physically active with her two teenage sons, 16 and 14: The family often plays tennis together. She travels frequently to medical conferences, which she said provides social stimulation and connection.

But she admits there are areas where she could improve.

“To be honest sleep and relaxation may not be as good always with the traveling,” adding that when it comes to sleeping - a recent study found 6.4 to 7.8 hours of sleep a night may be the sweet spot - “That part I should improve.”

Another goal is learning something entirely new - possibly scuba diving, which the rest of her family has already done.

“I want to start a new hobby but it’s not easy to do,” she said. “Sometimes when you are 50-plus it’s easy to get stuck doing old things.”

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