Dementia Risk Is Double Earlier Estimates, Even Higher for Black Americans

Study shows alarming increase in expected cases, though lifestyle changes can reduce risk

Liz Szabo,

AARP

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Published January 13, 2025

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Americans face a much higher risk of dementia than estimated in previous reports, according to a new study in Nature Medicine.

The research projects the lifetime risk of dementia for a 55-year-old to be at least 36 percent for those living to age 95, a rate twice as high as reported in earlier studies.

The researchers suggest that their estimates are higher because they took extra measures to avoid underestimating the number of dementia cases. They closely tracked the health of the study’s 15,000 participants over an average of more than two decades. Participants underwent cognitive exams during in-person visits and were also interviewed by phone. The team also examined medical records and spoke to many study participants’ family members or caregivers about any memory problems.

The findings may still underestimate the rate of dementia, the study authors say. Although 42 percent of people age 55 and older in their study developed dementia by age 95, researchers could only confirm that diagnosis for 36 percent, says study co-author Marilyn Albert, director of the Johns Hopkins Alzheimer’s Disease Research Center and a member of AARP’s Global Council on Brain Health (GCBH).

As the population ages, the number of Americans affected by dementia — both as patients and caregivers — will rise. The study projects that the number of U.S. adults who develop dementia each year, estimated at about 514,000 in 2020, will increase to about 1 million in 2060. The risk is most pronounced in Black adults.

Dementia risk rose sharply with age in the study. It remained low from age 55 to 75, at 4 percent, rising to 10 percent at 80, says Michael Fang, the study’s first author and an assistant professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health.

“The findings are very sobering,” Albert says. “This tells us how really serious the problem of dementia is in the United States.” Dementia is an umbrella term for conditions that impair a person’s ability to think, reason and remember to levels that interfere with daily life. It can be caused by several different diseases, the most common is Alzheimer’s disease.

Women and Blacks at higher risk

Women are more likely to develop dementia because they tend to live longer than men, Albert says. Risk differences between the sexes emerged starting at age 85. People with the APOE-e4 genetic mutation, also have a much higher risk than average.

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Black people developed dementia more often and at younger ages than white people, the researchers found. In the study, Black participants developed dementia at a median age of 79, compared to 82 among white people.

While the lifetime risk of dementia in white study participants was 3 percent by age 75, the risk for Black participants at the same age was 7 percent. By age 85, the lifetime risk of dementia in white participants was 18 percent, compared to 28 percent in Black participants at the same age.

While dementia diagnoses will double among white people by 2060, they will triple among Black people in the same period, the study found. Although the new study didn’t explore why Black people developed dementia at earlier ages, Black adults tend to have more risk factors for dementia, including high blood pressure and diabetes, Fang says. In addition, discrimination can cause physical and mental stress, which may increase the risk of dementia, according to the GCBH. Racial and ethnic minorities also tend to have fewer of the educational and economic opportunities that appear to reduce the risk of dementia.

Researchers, who launched the study in 1987, deliberately enrolled a large number of Black people, who have been underrepresented in many earlier studies. In the new study, Black people made up 27 percent of participants, who were recruited from Forsyth County, North Carolina; Jackson, Mississippi; Minneapolis, Minnesota; and Washington County, Maryland.

Although the new study presents some of the most comprehensive data yet on dementia risk in Black people, “we can’t really say it’s nationally representative,” notes Hugo Aparicio, M.D., associate professor of neurology at Boston University, who was not involved in the research. Mainly because the study included few Asian, Hispanic or Native American participants. “But it gives us maybe one of the best estimates of risk [for] the African American population that we’ve had.”

Cognitive decline is not inevitable

“We need to do a much better job at getting out the message that much of this risk is preventable,” says Josef Coresh, M.D., the study’s senior investigator and epidemiologist and the founding director of the Optimal Aging Institute at NYU Langone.

A 2024 Lancet Commission Report concluded that 40 percent of global dementia cases are potentially preventable with lifestyle changes.

“It is never too early or too late to start protecting our brains,” says Gary Small, M.D., chair of psychiatry at Hackensack University Medical Center. Adults can reduce their risk of dementia in numerous ways by addressing risk factors such as stress, obesity, high blood pressure, diabetes and hearing loss, Small says. Research also shows the importance of restful sleep and social engagement.

“If we institute prevention efforts in early life and midlife, we may be able to actually reverse some of these trends that we're seeing,” Aparicio says.

Researchers funded by the Alzheimer’s Association are expected to publish results in July from a two-year clinical trial that studies whether making several lifestyle changes simultaneously can protect older adults from cognitive decline.

On a societal level, Coresh says, lawmakers and regulators should work to improve childhood education and nutrition, which have been linked to a lower risk of cognitive decline in later life.

The new study is “a wake-up call to policymakers,” says GCBH member Jason Karlawish, M.D., who is co-director of the Penn Memory Center and a professor at the University of Pennsylvania School of Medicine.

Karlawish, who was not involved in the new study, said he would like to see policy makers better address dementia risk factors, such as obesity; promote healthier diets and exercise; and make hearing aids more accessible.

“There are very doable, actionable policy solutions to make people healthy,” he says.

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