Dementia is a worsening public health crisis. But data shows that certain populations are significantly less likely to develop dementia than their predecessors. A Duke researcher wants more people to acknowledge the good news — and turn it into prevention guidance for all.
Many indicators suggest that dementia has become a full-blown public health crisis. Looking at just the Alzheimer’s Association’s annual Facts and Figures report, for example, there are 7 million people living with Alzheimer’s today compared to 5.8 million just six years ago. But decades of data show that as the population grows and the number of dementia cases rises year over year, a trend has been emerging: People today — especially in higher-income countries — are actually less likely to develop dementia than their parents or grandparents were at the same age.
Duke University actuarial researcher Eric Stallard recently issued a report in the Journal of the American Medical Association pointing out that multiple studies point to a 67-percent decline in the prevalence rate of dementia in the United States over the past 40 years. The causes behind this shift aren’t fully understood, but Stallard — who has studied public health in the U.S. for more than 50 years — argues that this good news deserves more attention — and that we should be asking urgent questions about how to protect and accelerate these gains for future generations.
“The assumption that no progress has been made is just wrong,” Stallard told Being Patient. “Huge progress has been made.”
An unexpected trend
Since the 1980s, modern medicine has continued to extend more and more people’s lives. Experts have been in disagreement over how much of a societal burden dementia would become. Some scientists assumed that the average age of onset for dementia would not change, and the fact that more people were living longer years would lead to huge increases in diagnoses. Others argued that the same factors that increase average life spans would also delay the onset of dementia, and the prevalence of the disease would decline—even if the total number of cases increased.
Stallard and his colleagues first published evidence supporting the latter theory in 2016. They analyzed data from the National Long-Term Care Survey collected between 1984 and 2004, where, every five years, the researchers had asked 20,000 participants over the age of 65 for information about their medical conditions, education levels, and income. “What we found out was that there was a decline of just shy of 2.75 percent per year in the prevalence rates” of dementia, Stallard said.
In the years since, other researchers have published similar results. According to data from the Health and Retirement Study, dementia prevalence declined from 11.6 percent in 2000, to 8.8 percent in 2012. Data from the National Health and Aging Trends Study showed a similar drop in dementia prevalence between 2011 and 2021. This trend has been observed in Europe as well.
Based on the two U.S. studies, Stallard felt confident that the decline he observed between 1984 and 2004 had continued through the next two decades. Extrapolating from 2004 to 2024, he found that prevalence rates of dementia have likely declined as much as 67 percent over the past 40 years, even as the number of older adults has increased.
Why is are dementia rates on the downturn?
Scientists in the field are still trying to make sense of these declining trends. The researchers who analyzed the HRS data found that older adults in 2012 reported completing more years of formal education, suggesting that cognitive stimulation may help prevent dementia.
On the other hand, older adults in 2012 had higher rates of obesity and diabetes, which have both been linked to dementia. But the researchers pointed out that treatments for metabolic and cardiovascular diseases have also improved, potentially offering more recent generations better protection against the worst outcomes of these conditions.
There is some evidence that younger generations are maintaining healthier blood vessels in their brains. Scientists at Rush University examined 25 years of autopsy data from the Religious Orders Study and the Memory and Aging Project and reported their results in 2023. Although the prevalence of problematic protein formations like amyloid plaques, tau tangles, and Lewy bodies did not decline over time, rates of atherosclerosis and arteriosclerosis in the brain did. The researchers suggested that healthier blood vessels could be making people more resilient to the molecular changes that cause neurodegenerative disorders. The Rush University researchers also argued that nationwide public health efforts to improve vascular health were responsible for these positive developments and advocated for redoubling those efforts.
Stallard said he thinks it’s essential for researchers to continue probing these questions to figure out what has driven the decline in dementia rates — and how these benefits can be maintained and built upon. The answers may not change much for people who are in or approaching their retirement years today, but this new generation of older adults is already on track to be healthier than their predecessors. Meanwhile, whatever answers scientists find will produce insights that could help today’s young and middle-aged people predict — and hopefully lower — their lifetime risk of developing dementia.
Andrew Saintsing (@AndrewSaintsing) earned a PhD in biology, and now he writes about science for outlets like Drug Discovery News.
