The number of people in the United States who develop dementia each year will double over the next 35 years to about one million annually by 2060, a new study estimates, and the number of new cases per year among Black Americans will triple.
The increase will primarily be due to the growing aging population, as many Americans are living longer than previous generations. By 2060, some of the youngest baby boomers will be in their 90s and many millennials will be in their 70s. Older age is the biggest risk factor for dementia. The study found that the vast majority of dementia risk occurred after age 75, increasing further as people reached age 95.
The study, published Monday in Nature Medicine, found that adults over 55 had a 42 percent lifetime risk of developing dementia. That is considerably higher than previous lifetime risk estimates, a result the authors attributed to updated information about Americans’ health and longevity and the fact that their study population was more diverse than that of previous studies, which have had primarily white participants.
Some experts said the new lifetime risk estimate and projected increase in yearly cases could be overly high, but they agreed that dementia cases would soar in the coming decades.
“Even if the rate is significantly lower than that, we’re still going to have a big increase in the number of people and the family and societal burden of dementia because of just the growth in the number of older people, both in the United States and around the world,” said Dr. Kenneth Langa, a professor of medicine at the University of Michigan, who has researched dementia risk and was not involved in the new study.
Dementia already takes an enormous toll on American families and the country’s health care system. More than six million Americans currently have dementia, nearly 10 percent of people 65 and older, research has found. Experts say that each year in the United States, dementia causes more than 100,000 deaths and accounts for more than $600 billion in caregiving and other costs.
If the new projections are borne out, there will be about 12 million Americans with dementia in 2060, said Dr. Josef Coresh, director of the Optimal Aging Institute at New York University’s Grossman School of Medicine and a leader of the study, which involved about 100 researchers at 10 universities.
The study reinforces the urgency of trying to prevent or slow the onset of dementia, the authors and other experts said. Their major recommendations are to improve people’s cardiovascular health with medication and lifestyle changes; increase efforts to prevent and treat strokes, which can lead to dementia; and encourage people to wear hearing aids, which appear to help forestall dementia by allowing people to be more social and cognitively engaged.
“One needs to see the huge magnitude of the issue,” said Alexa Beiser, a professor of biostatistics at Boston University School of Public Health, who was not involved in the new study but evaluated it as an independent reviewer for the journal. “It’s enormous, and it’s not equally distributed among people,” Dr. Beiser added, noting that the study found disproportionate risk for Black Americans.
The researchers evaluated over three decades of data from a long-running study of the health of people in four communities — in Maryland, Mississippi, Minnesota and North Carolina. About 27 percent of the 15,000 participants were Black, primarily from Jackson, Miss., Dr. Coresh said. The analysis, which was funded by the National Institutes of Health, focused on Black and white participants because there were not many participants from other racial and ethnic groups, the authors said.
The study estimated that the number of new annual cases among Black people would surge to about 180,000 in 2060 from about 60,000 in 2020. The main reason for the tripling of new cases in that population is that the percentage of Black Americans living to the oldest ages is growing faster than among white people, Dr. Coresh said.
In the study, Black participants also developed dementia at younger average ages than white participants and had 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,” Dr. Coresh said, noting that hypertension, diabetes and high cholesterol increase dementia risk. He said lower socioeconomic status and education levels among the study participants may have also played a role, as well as structural racism that has affected health.
Predicting dementia risk is complicated for several reasons. The causes of dementia vary and are often not completely understood. Types of dementia also vary and can overlap with each other. The new analysis, like several other studies, did not try to estimate how many people would develop Alzheimer’s disease, the most common type of dementia. That is because many experts believe that aspects of Alzheimer’s can overlap with vascular dementia and that both conditions can be fueled by cardiovascular issues, Dr. Coresh said.
Several studies in America and globally have found the percentage of dementia cases among older adults has declined in recent years, most likely because of better treatment for cardiovascular problems and a more educated population, since education can improve brain resilience and overall health.
That decrease doesn’t contradict the new study, experts and the authors said, because the study estimated the current level of cumulative dementia risk over people’s lifetimes and projected it forward. It’s possible that positive changes — healthier behaviors and better treatment for conditions like diabetes and stroke, for example — could lower the rate of risk at any given age in future decades, but the number of new cases each year will still increase from the current number, 514,000, because of the growing population of older people, experts said.
“Whether it’s a million people or 750,000 people a year, there’s going to be a lot of people, and the longer people live, the more dementia there’s going to be,” said Dr. Beiser, who has worked on earlier studies of different patients that have found lower estimates.
The study also found that women had a higher lifetime dementia risk than men — 48 percent compared with 35 percent. Dr. Coresh said that was primarily 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.
Dr. Langa said other researchers were trying to learn whether there might also be biological differences that increase women’s risk, possibly “the hormonal environment in the body or even potential genetic differences that might be affecting women’s brains in different ways than men’s.”
Another high-risk group was people with two copies of the gene variant APOE4, which greatly increases the risk for Alzheimer’s disease and of developing it at younger ages than people without that variant. In the study, people with two copies of APOE4 had a lifetime dementia risk of 59 percent compared with lifetime risks of 48 percent for people with one copy and 39 percent for people without the variant.
The analysis used health data from the Atherosclerosis Risk in Communities study (known as ARIC), following people aged 55 and older from 1987 to 2020.
Researchers used several methods to determine if and when participants developed dementia. About a quarter of the cases were diagnosed with in-person neuropsychological testing, while others were identified through hospital records or death certificates or through telephone assessments. Each method has limitations, which could lead to overestimation or underestimation of the actual numbers of dementia patients, experts said.
The study found that at age 75, dementia risk was about 4 percent; at 85, it was 20 percent; and at 95 it was 42 percent. The researchers applied the risk percentage to population projections from the census to estimate future annual dementia diagnoses.
To reduce one’s chances of developing dementia, experts and the study authors emphasized taking steps to address known risk factors like diabetes, high blood pressure and hearing loss. A recent report by the Lancet commission on dementia listed 14 risk factors that can be improved and concluded that “half of dementia risk is preventable and it is never too early or too late to address dementia risk,” Dr. Coresh said.
Experts recommended such steps rather than seeking out the new drugs for Alzheimer’s, which appear only to be able to modestly slow cognitive decline in early stages of the disease and which carry safety risks.
“Because of their relatively limited efficacy, I don’t think you get a huge bang for decreasing lifetime risk from that,” Dr. Langa said about the new drugs. “I do think that we’ll get more bang for the buck from some of these public health and lifestyle interventions that seem to improve health generally and decrease dementia risk over time.”
