New research suggests that the risk for developing dementia is significantly higher than previously estimated, and the burden on the United States population will grow substantially over the next few decades.
Overall, more than 2 in 5 people over the age of 55 in the US – about 42% – will develop dementia in their later years, according to a study published Monday in the journal Nature Medicine.
As the US population ages, the number of people diagnosed with dementia each year is projected to double – from about 514,000 cases in 2020 to about 1 million a year by 2060.
Much of this trend will be driven by the large cohort of Baby Boomers reaching older age, the researchers wrote.
The Boomer generation, born from 1946 to 1964, is the second largest in the US after their children, the Millennials, according to the US Census Bureau: There were about 73 million people in the Boomer generation in 2020, the youngest of whom are now at least 60 years old.
By 2040, all Baby Boomers will be at least 75 years old, an age after which dementia diagnoses were found to increase substantially. Only about 17% of cases were diagnosed before age 75, according to the new research, with an average age of 81.
For this study, researchers tracked the health records of about 15,000 people, following each patient for an average of 23 years. Their data was more diverse than previous studies that have estimated dementia prevalence, with Black people representing more than a quarter of participants, and more comprehensive measures to capture diagnoses.
The shifting racial makeup of the US population may also play a role in the rise of dementia cases, the researchers said, with higher-risk minority groups expected to comprise more than half of the US population by 2045.
The researchers found “striking differences” in dementia risk by race, with significantly higher diagnoses rates among Black adults and earlier onset compared to White adults. Annual dementia diagnoses among Black adults may triple by 2060, according to the new estimates.
“Racial disparities in dementia may reflect the cumulative effects of structural racism and inequality throughout the life course,” the researchers wrote. “For instance, poor access to education and nutrition may contribute to earlier differences in cognitive reserve, and socioeconomic disparities and limited access to care may lead to a higher burden of vascular risk factors at midlife.”
Older women have a higher overall risk of developing dementia in their lifetime than older men – about 48% compared with 35%, the new research estimates – but much of that difference is due to the fact that women tend to live longer.
And older adults with a particular gene – apolipoprotein E, or APOE, which is involved with the process of carrying cholesterol and other fat through the bloodstream – are also at higher risk. Older adults with two copies of the gene had a 59% risk of developing dementia in their older age, compared with 48% of those with one copy and 39% of those with no copies of the gene, the new study found.
While the rising burden from dementia is driven largely by age and genetic factors, experts say that there are “broad opportunities” to reduce risk in the population with better management of certain lifestyle factors such as a healthy weight and diet, mental health and hearing loss.
“Accumulating data from clinical trials have linked healthy lifestyle behaviors, the absence of vascular risk factors and hearing rehabilitation with improved cognitive outcomes,” the researchers wrote. “However, only approximately 20% of US adults are meeting recommended lifestyle and cardiovascular health targets, and only approximately 30% of older adults with hearing loss are using a hearing aid.”
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And for the first time, new diagnosis criteria published by the nonprofit Alzheimer’s Association in July, calls on doctors diagnosing the condition to rely on biomarkers — pieces of beta amyloid and tau proteins picked up by lab tests or on brain scans — rather than pen-and-paper tests of memory and thinking.
The novel diagnosis criteria aims to catch Alzheimer’s disease, the most common form of dementia, in its earliest and most treatable stages – with novel drugs that aim to slow the progress of the disease on the horizon. But the clinical trials for those drugs have been “plagued by a lack of racial diversity,” experts say.
The findings from the new research highlight an “urgent need for policies that enhance healthy aging, with a focus on health equity,” the researchers wrote. “Policies that enhance prevention and healthy aging are urgent public health priorities for reducing the substantial and growing burden of dementia.”