A new study from NYU Langone Health’s Optimal Aging Institute, published in Nature Medicine, shows that Americans’ risk of developing dementia after age 55 is 42 percent—more than double the risk estimate reported by previous studies. The new estimate, which translates into a half-million cases this year and a million new annual cases by 2060, is directly tied to an aging population and higher incidence of chronic disease.
Here’s a closer look at the study’s key takeaways, why these findings differ sharply from previous projections, and how they could inform preventive strategies.
Who was studied and what were the key findings?
The multi-center collaboration examined data from the ongoing Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS), which has tracked vascular and cognitive health in nearly 16,000 aging participants since 1987. Researchers found that from 1987 until 2020, documented dementia was found in 3,252 participants, translating to a lifetime risk of 42 percent after the age of 55. The risk was 4 percent by age 75 years, 20 percent by age 85, and 42 percent by age 95, emphasizing that more than half the risk is among those who survive past age 85 years.
Lifetime risks for dementia were higher in women, Black adults, and carriers of a variant in the APOE4 gene, which codes for a lipid-carrying protein and is considered the greatest monogenetic driver of late-onset Alzheimer’s disease.
Why does this new data diverge so dramatically from previous dementia risk estimates?
Senior study author and population health expert Josef Coresh, MD, PhD, says the steep rise in expected dementia incidence is attributable in large part to population age. “A progressive decline in brain function is often observed starting in middle age,” he says. “Plus, women overall live longer than men, and about 58 million Americans are now over age 65.”
Additional explanations for the previous underestimates of dementia risk include unreliable documentation of the condition in health records and on death certificates; minimal surveillance of early-stage cases; and underreporting of cases among racial minority groups, who are disproportionately vulnerable. Notably, ARIC-NCS is the longest-followed cohort of African Americans for researching cognition and heart health.
Were any additional findings from the study associated with a higher risk for dementia?
Beyond aging and genetic factors, previous findings from ARIC-NCS and other studies indicate that a high risk of dementia is also linked to high rates of hypertension and diabetes, obesity, unhealthy diet, lack of exercise, and poor mental health.
Loss of hearing in older adults has also been tied to an increased risk for dementia. Further, only one-third of Americans with hearing loss use hearing aids.
What do these results mean for clinicians who are caring for older patients?
According to Dr. Coresh, clinicians should emphasize the same prevention strategies that help to reduce the risk of metabolic and cardiovascular disease, including healthy diet and exercise. Given the link between dementia and hearing loss, regular hearing monitoring, testing, and intervention can also help to mitigate risk, as detailed in the report of the Lancet Commission on dementia.
“The good news is, it’s never too early—or late—to reduce your dementia risk by as much as half with these approaches,” he says.
Any other takeaways from this study?
In light of the population boom—and the corresponding growth in dementia cases—public health strategies such as blood pressure control and diabetes prevention programs are needed to help minimize the drivers of dementia.
Additionally, Dr. Coresh argues that more resources are needed to address racial inequities that drive poorer outcomes, including dementia incidence, among Black adults. “Policies should heighten efforts in Black communities to improve childhood education and nutrition, which we know can stave off cognitive decline later in life,” he adds.
