Dementia Cases to Double in the U.S.

Dementia cases in the U.S. are expected to double in the next four decades, a new analysis suggested.

In a racially and geographically diverse sample, the lifetime risk of dementia was estimated at 42% (95% CI 41-43) with incidence increasing substantially after age 75, according to Josef Coresh, MD, PhD, of New York University Grossman School of Medicine in New York City, and co-authors.

Based on U.S. Census data, the number of adults who will develop dementia each year was projected to increase from about 514,000 in 2020 to 1 million in 2060, Coresh and colleagues reported in Nature Medicine.

Projected rates were highest in Black adults, women, and APOE4 carriers, with lifetime risks ranging from 44% to 59% in these groups. Mortality was treated as a competing event.

“It’s important to note that the risk from ages 55 to 75 is 4%,” Coresh told MedPage Today. “It rises to 20% by age 85 and then 42% by age 95, so half the risk is after age 85.”

The lifetime risk figures are considerably higher than previous estimates. Data from the Framingham Heart Study data suggested, for example, that about 14% of men and 23% of women in the U.S. would develop dementia during their lives.

The new estimates came from a more diverse group of people followed from 1987 to 2020, using an extensive range of methods to ascertain dementia, Coresh pointed out. It relied on data from the Atherosclerosis Risk in Communities (ARIC) cohort, which was more diverse geographically, racially, and socioeconomically than other studies, he added.

The analysis extends existing research by quantifying the growth of incident dementia, incorporating trends that likely will be driven by the Baby Boom generation reaching older ages, the researchers said. The findings highlight the importance of strategies to reduce dementia risk and address racial inequities in healthcare, they added.

“We now know that half of dementia risk is preventable,” Coresh said. “The Lancet Commission summarized the latest evidence, including the value of controlling vascular risk factors like blood pressure, obesity, diabetes, and smoking; optimizing exercise and sleep; and countering social isolation and depression. In later ages, addressing hearing and vision limitation is important, as is preventing falls and head injuries.”

In the U.S. and globally, there’s an urgent need to address the crisis of Alzheimer’s disease and dementia, noted Maria Carrillo, PhD, chief science officer and medical affairs lead for the Alzheimer’s Association in Chicago, which wasn’t involved with the study.

“In the coming years, more people will be affected,” Carrillo said. “This is especially true for high-risk groups who often have been underrepresented in research, including Black Americans, Hispanic Americans, and women.”

The ongoing POINTER trial is evaluating whether lifestyle interventions that simultaneously target several risk factors can protect cognitive function in people at increased risk for cognitive decline, she added.

Coresh and colleagues evaluated health records from 15,043 participants in the community-based, prospective ARIC cohort in North Carolina, Mississippi, Minnesota, and Maryland who were 55 and older. All were dementia-free at age 55.

The sample included 55.1% women and 26.9% Black participants. About a third (30.8%) of participants had at least one APOE4 allele.

Over a median follow-up of 23 years, there were 3,252 incident cases of dementia. Of the dementia cases, 49% were diagnosed through phone interviews, 27% through hospital and death record review, and 24% at study visits with cognitive testing.

Differences in risk across race emerged at about age 75, while sex differences emerged at about age 85. Lifetime risks were 41% in white versus 44% in Black participants, and 35% in men versus 48% in women, due perhaps to women’s higher life expectancy.

People with two APOE4 copies had a higher lifetime risk of dementia (59%) than those with one copy (48%) or no copies (39%), with differences starting at around age 70.

The analysis had several limitations, the researchers acknowledged. Some dementia cases may have been misclassified, and some cases might not have been captured. The study also was not externally validated.

“Future population-based studies with long follow-up and comprehensive dementia ascertainment are needed to validate our lifetime risk estimates,” they wrote.

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