New research suggests many older Americans may incorrectly estimate their chances for developing dementia.

Almost half of adults questioned believed they were likely to develop dementia. Signs of the condition include changes in personality and memory loss. Alzheimer's disease is one form of dementia.

The research suggests many people did not understand the link between physical health and brain health or how racial differences could affect one's dementia risk.

A report on the study appeared in JAMA Neurology, a publication of the Journal of the American Medical Association.

The survey was based on information from the University of Michigan National Poll on Healthy Aging. One thousand adults from across the United States completed an online questionnaire in October 2018. All the men and women were 50 to 64 years of age.

Many subjects who rated their health as fair or poor thought their chances of developing dementia were low. At the same time, many who said they were in excellent health said they were likely to develop the disease.

Many said they tried at least one of four unproven memory-protecting methods, including taking dietary supplements like fish oil and ginkgo. The most popular method for keeping the mind active was doing crossword puzzles.

Keith Fargo supervises research and outreach programs at the Alzheimer's Association, a not-for-profit group. He was not involved in the study. Fargo says there is strong evidence that activities more challenging than puzzles can help protect against dementia. He suggested activities such as playing chess, taking a class and reading about subjects not well-known to the reader.

Research has shown that regular exercise, a healthy diet, limiting alcohol and not smoking make dementia less likely. Supplements have not been shown to help.

Donovan Maust is the study's lead author and a geriatric psychiatrist at the University of Michigan. He said researchers have not done a good job of informing the public that "there really are things you can do to lower" the risk of dementia.

The online survey asked people to estimate their likelihood of developing dementia. It also asked whether they had ever discussed ways to prevent the condition with their doctor. Few people said they had.

Maust said the survey results raise concerns because doctors can help people control high blood pressure and diabetes – two conditions often linked with dementia risk.

Among those who said their physical health was only fair or poor, close to 40% thought they were at low risk for Alzheimer's disease or other dementia. Almost the same percentage rated their chances as likely even when they reported being in very good or excellent physical health.

In the survey, more whites than blacks or Hispanics believed they were likely to develop dementia. But only 93 blacks were questioned, making it difficult to generalize for the U.S. population. Across the country, non-whites face higher risks for dementia than whites. The Alzheimer's group operates programs in black and Hispanic communities.

Keith Fargo said, "There's lots of work to do ... to educate the public so they can take some actions to protect themselves."

The Alzheimer's Association reports that one in three older Americans die with Alzheimer's or other dementias. There are currently no medicines or medical treatments proven to prevent the condition. But some European studies have shown that healthy lifestyles may help prevent mental decline. The Alzheimer's Association is supporting similar research in the U.S.

I'm Kelly Jean Kelly.

Lindsey Tanner reported this story for the Associated Press. Jonathan Evans adapted it for VOA Learning English. George Grow was the editor.

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challenging – adj. difficult in a way that is usually interesting or enjoyable

crossword puzzle – n. a puzzle in which words that are the answers to clues are written into a pattern of numbered squares that go across and down

geriatric – adj. of or relating to the process of growing old and the medical care of old people; of or relating to geriatrics

regular – adj. happening over and over again at the same time or in the same way : occurring every day, week, month, etc.

supplement – n. something that is added to something else in order to make it complete