Study details

For the study, researchers looked at data on more than 15,000 people who were part of the Atherosclerosis Risk in Communities study, which initially started in 1987 to track cardiovascular risk and is funded by NIH. The population of the study included people from Maryland, North Carolina, Mississippi, and Minnesota, and focused on Black and white participants, as there weren't many participants from other racial and ethnic groups.

The study estimated that the number of Americans who develop dementia each year will double over the next 35 years to around one million people annually by 2060. This increase will largely be due to the growing aging population, since Americans are living longer than previous generations.

According to Josef Coresh, a leader of the study and director of the Optimal Aging Institute at New York University's Grossman School of Medicine, if the new projections are borne out, there will be around 12 million Americans with dementia in 2060.

The study also estimated that the number of new annual dementia cases among Black people would hit around 180,000 in 2060, up from around 60,000 in 2020, largely because the percentage of Black Americans living to the oldest ages is growing faster than it is among white people, Coresh said.

Black participants in the study were also found to develop dementia at younger ages than white participants and had a higher lifetime risk.

"I don't know that we fully understand it, but at least some of the contributing factors are that the vascular risk factors are more common," Coresh said, adding that hypertension, diabetes, and high cholesterol increase a person's risk of dementia. Lower socioeconomic status and education levels among the study participants could have also played a role, as well as structural racism that has affected health, Coresh added.

The study also found that adults over 55 had a 42% lifetime risk of developing dementia, a significantly higher risk than previous estimates, which the authors said was due to updated information about Americans' health and longevity and the fact their study population was more diverse than previous studies.

However, Coresh noted that "the risk from ages 55 to 75 is 4%. It rises to 20% by age 85 and then 42% by age 95, so half the risk is after age 85."

Women had a 48% risk of developing dementia compared to 35% among men, a finding that Coresh said was largely because women in the study lived longer. "Their risk of getting dementia by the time their 95th birthday would arrive is higher because more of them will make it closer to their 95th birthday," he said.

People with two copies of the APOE4 gene variant also saw higher risks of developing dementia, with a 59% risk compared to 48% among people with one copy and 39% among people without the variant.

Theo Vos, an epidemiologist and emeritus professor at the University of Washington, said that dementia is a difficult condition to consistently measure, partly because norms around listing it as a cause of death have varied over time and by country. There has also been variability in the criteria and tests used to diagnose someone with dementia.

"The strength of this study is that they followed people up over time, and they kept probing for signs that would confirm, or not, a diagnosis of dementia," Vos said. "That's a strength because with dementia being a progressive disease, it may be hard in the beginning to say is this, or is this not dementia. But give it another three, four, five years and it’s pretty obvious whether it is or is not."

While the new data is stark compared to previous numbers, Andrea Bozoki, division chief of cognitive and behavioral neurology at the University of North Carolina School of Medicine, said people should keep in mind that not everyone will develop dementia in their old age.

"Less than half of people who make it to age 95 will have dementia," she said. "Dementia is not an inevitable part of aging, no matter how old you are."

How to reduce your dementia risk

Many dementia cases could be preventable, as research published in The Lancet last year found that 45% of dementia cases worldwide are potentially preventable.

"All of the things that we know are good for health in general are good for preventing dementia," said Christine Kistler, an associate professor in the University of Pittsburgh's division of geriatric medicine. "Quitting smoking at any age is good for you. Starting to exercise at any age is good for you. We need to keep our brains working and that helps keep our brains healthy."

Here are some things experts recommend you do to reduce your dementia risk:

• Try a plant-based diet: Research has found that high vegetable intake can slow the rate of age-related cognitive decline, and another study found that eating minimally processed plant-based foods alongside regular exercise, stress reduction, and support groups could improve mild cognitive impairment symptoms.
• Exercise regularly: Exercise not only controls weight and reduces heart disease risk as well as other health conditions, it also reduces dementia risk, research has found.
• Get your vaccines: Studies of the shingles and flu vaccines have found they have been linked to a reduced risk of Alzheimer's disease and other dementias in vaccinated people.
• Take a daily multivitamin: Daily multivitamins could help slow memory loss in people ages 60 and older by around two years, according to one study.
• Stay away from air pollution: Research has suggested that exposure to pollutants increases dementia risk, and that better air quality lowers it.
• Protect your hearing: Protecting yourself from hearing loss by using earplugs, sound-blocking headphones, or earmuffs can reduce your risk of dementia, research has found.
• Stay socially connected: Research has suggested that people who stay socially connected are less likely to develop dementia than those who are isolated and lonely.
• Monitor your blood pressure, blood sugar, and cholesterol: Hypertension has the potential to increase the danger of stroke, which raises the risk of vascular dementia. Meanwhile, high blood sugar leads to diabetes, which can increase your risk of cognitive impairment. Lowering your cholesterol can reduce your risk of dementia.
• Get enough sleep: Research has suggested that insomnia and daytime sleepiness are associated with an increased risk of developing Alzheimer's disease.
• Drink less alcohol: Alcohol can exacerbate a number of health disorders like diabetes, hypertension, stroke, and memory deficits, which can all raise dementia risk. Drinking also increases the risk of liver disease and the danger of falls, car crashes, and other injuries that can lead to traumatic brain injuries.