You’ve heard the saying before: “use it or lose it.” Studies show that people who utilize their brains more—by furthering their education, learning a new language or musical instrument or keeping a rich network of relationships with family and friends—tend to have lower rates of dementia and problems with their thinking later in life. Nothing can completely prevent a certain amount of decline in cognitive functions that comes with age (that’s normal) but keeping the brain in good working order can lessen the consequences.

Here’s what the latest science suggests about what can—and can’t—prevent cognitive decline.

Education

In a new study published in Neuroepidemiology that analyzed results from the memory tests of more than 11,000 older Europeans, researchers found that education can combat cognitive decline—to a point.

People took recall tests at the start of the study and every two years for nearly a decade, and when the scientists compared those results with the diagnoses of dementia or cognitive impairment, they found that people with higher education seemed to have lower rates of dementia.

But when the researchers then looked at what happened to the people who were diagnosed with dementia, they found that education didn’t seem to affect the rate at which the people’s cognitive functions declined. In other words, it didn’t matter how much education the people had once the dementia began.

That doesn’t mean that education isn’t an important part of preventing dementia. Dorina Cadar, a research associate in the department of behavioral health science at the University College of London and the study’s lead author, says that education gave people a larger cognitive reserve, so once cognitive decline began, it took them longer to experience the effects of the age-related slowing in their thinking abilities. Like a well-padded bank account, having more cognitive reserve gives people greater room to compensate for areas of the brain that might be failing over time. She notes that even an extra year of education can help people recall one additional word in recall tests years later. Even if learning more can’t prevent cognitive decline, it can make the effects of compromised thinking less obvious, and potentially less intrusive on a person’s daily life.

Crossword puzzles, having friends and learning new languages

Studies continue to support the fact that people who play cards, read or have strong friendships tend to develop dementia later than those who don’t engage in these activities. But some research is starting to suggest that the benefit may stop there. One study of nearly 1,200 older people found that while those who stay mentally active may experience dementia later, once dementia begins, they decline more quickly than those who aren’t so intellectually active.

That may reflect the fact that people with more active brains, or a higher level of education, may indeed have greater reserves on which they can draw as their brains start to decline. But once these reserves are dry, like a tapped-out bank account, there’s nothing left to keep the brain going.

More research is needed to fully understand how such backup systems affect aging-related decline, but experts still say that it’s best to start off with as large a reserve as possible. Keeping the brain active and engaged by seeing friends, visiting museums or learning new skills is one way to do that.

Exercise

Many other factors affect how the brain ages, including physical activity, heart health, mental illness, sleep and diet. But the role of exercise may be especially important. A recent study of more than 1,600 people over age 65 found that those who spent more time sitting had the same risk of developing dementia as people who carry a genetic mutation that puts them at higher risk of Alzheimer’s.

Being physically active may help the brain by keeping the heart fit. Studies show that some of the same risk factors for heart disease, such as high cholesterol levels, high blood pressure and diabetes, may also put people at greater risk of developing dementia. Poor heart health also means less blood flow to the brain, which is essential for nourishing brain nerves and maintaining healthy nerve connections.

“We should really look at not just a single individual factor but a combination of factors: exercise, a healthy diet, having contact with friends and relatives,” says Cadar. “Together, they seem to help people in older age.”

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