Many Americans believe they are likely to develop dementia — and they often turn to unproven ways to try to better their odds, a new study suggests.

In a survey, researchers found that almost half of Americans in their 50s and 60s believed they were at least “somewhat likely” to develop dementia. Yet few — 5% — said they had talked to their doctor about ways to lower their risk.

Instead, one-third or more were taking fish oil, vitamin E or other supplements to help ward off memory decline — even though none have been proven to have such benefits.

“It certainly seems like people believe that supplements or fish oil help preserve their memory,” said lead researcher Dr. Donovan Maust, a geriatric psychiatrist at the University of Michigan, in Ann Arbor.

Maust said that might reflect “excitement” over initial research suggesting that certain supplements might ward off memory decline — excitement that wasn’t tempered when later studies failed to show benefits.

The findings, published online Nov. 15 in JAMA Neurology, are based on 1,019 adults aged 50 to 64 who were surveyed in 2018. They were asked whether they thought they were “somewhat likely,” “very likely” or “unlikely” to develop dementia in their lifetime.

Overall, 44% believed they were somewhat likely, while 4% chose the “very likely” option.

How accurate were they? It’s hard to say, since the terms are vague, according to Keith Fargo, director of scientific programs and outreach for the Alzheimer’s Association.

But, he added, it would be reasonable for anyone to see themselves as somewhat likely to develop dementia: Around 10% of Americans aged 65 and older have dementia; the rate soars to roughly one-third among people aged 85 and up.

Fargo, who was not involved in the study, said that more can be gleaned by looking at the responses of different groups of participants.

For example, black Americans were much more likely than whites to see themselves as unlikely to develop dementia: 63% endorsed that belief, versus 49% of white respondents.

In reality, black Americans have a higher rate of dementia.

Maust made the same point. “It’s striking,” he said, “that African American respondents thought their odds of developing dementia were half of non-Hispanic white respondents — when in fact their risk is more than twice as high.”

Fargo called that finding an “unfortunate surprise,” and said it points to a gap in public education efforts.

Respondents were also asked whether they were taking any of several measures to “maintain or improve” their memory. About one-third said they were using fish oil, while 40% said they were taking vitamins or other supplements. Over half said they did crossword puzzles.

None of those strategies are proven. Fargo did, however, note that crossword lovers might be the kind of people who maintain a generally “cognitively stimulating” life — and there is evidence to support benefits from doing so.

It’s thought that people with more education, or who engage in lifelong learning, may have more “cognitive reserve,” Fargo explained. The theory is, those people can withstand more of the brain damage that marks dementia before developing symptoms.

Studies are ongoing to figure out the best strategies for slowing or preventing dementia. Fargo said the Alzheimer’s Association is sponsoring a trial, called U.S. Pointer, that is testing a combination of tactics — including diet, exercise, and mental and social stimulation.

For now, Maust said the best bet is to take care of your overall health and control any chronic medical conditions — especially those that affect the heart and blood vessels, like high blood pressure and diabetes. Studies have long noted a connection between heart health and dementia, and a recent clinical trial showed that tight control of high blood pressure curbed older adults’ risk of mild cognitive impairment.

“I think people may not appreciate the extent to which risk of dementia can be reduced by addressing chronic medical conditions,” Maust said.

If you believe your memory or thinking skills are deteriorating, Fargo advised seeing your doctor.

“In some cases,” he said, “there may be a treatable underlying cause, like sleep apnea, vitamin-B12 deficiency or depression.”

More information

The Alzheimer’s Association has advice on preserving brain health.