A study of more than 214,000 older adults across 14 countries has revealed that the preventable risk factors behind dementia look very different depending on where someone lives.
The researchers assessed each participant for 12 modifiable risk factors identified in a major 2024 report.
These risk factors included hearing loss, depression, physical inactivity, and social isolation.
The report estimated that addressing all 12 risk factors could prevent or delay nearly half of dementia cases worldwide.
They tracked how risk factors traveled together within the same person.
A study of more than 214,000 older adults across 14 countries has revealed that the preventable risk factors behind dementia look very different depending on where someone lives.
Low education weighs on most older adults in China, yet touches barely one in ten Americans.
The result complicates a long-standing assumption in dementia research, which is that prevention advice worked out mostly in wealthy Western nations should apply neatly everywhere else.
If the leading risks differ by place, the strategies meant to cut them may have to differ as well.
A global blind spot
Almost everything scientists understand about preventing dementia comes from a small set of wealthy places, chiefly the United States, Britain, and Western Europe.
The rest of the world was barely studied. Whether those same lessons held elsewhere had never been tested at this scale, mostly because comparable data did not exist.
Emma Nichols, a research scientist at the University of Southern California (USC) Schaeffer Institute, set out to close that gap.
Nichols worked with colleagues at Brown University and Johns Hopkins University.
The team analyzed information from the Gateway to Global Aging Data project.
The project aligns with long-running national surveys so that answers from different countries can be compared directly.
A worldwide dataset
The pooled data covered more than 214,000 older adults across 14 countries and regions, gathered between 2009 and 2023.
The dataset extended far beyond the usual roster of wealthy nations, covering large parts of Asia, Latin America, and both wealthier and less affluent regions of Europe.
The researchers assessed each participant for 12 modifiable risk factors identified in a major 2024 report.
These risk factors included hearing loss, depression, physical inactivity, and social isolation.
The report estimated that addressing all 12 risk factors could prevent or delay nearly half of dementia cases worldwide.
Different countries, different risks
The contrasts were sharp. Low education is one of the earliest and strongest influences on later dementia. It applied to roughly 86% of older adults in China but only about 12% of those in the United States.
That gap is really a snapshot of history. The Chinese adults in the study grew up when schooling beyond a few years was uncommon.
Their American counterparts mostly stayed in class far longer – and those early gaps likely echo into old age.
Body weight ran in the opposite direction. Close to 45% of older Americans carried enough excess weight to register as a risk, measured through body mass index, compared with about 13% of people in India.
Each factor told its own geographic story. Smoking, blood pressure, and hearing loss all rose and fell from one country to the next, which meant no single prevention message could fit every population equally well.
Patterns shared across borders
What caught the team off guard was not the variation but the order tucked inside it. They tracked how risk factors traveled together within the same person.
The same groupings kept reappearing across societies that otherwise had little in common.
Heart-related risks moved as a pack, with high cholesterol tending to show up alongside high blood pressure.
Risky habits followed a similar pattern, with smoking and heavy drinking often occurring together. A third cluster linked social and sensory challenges, pairing isolation with hearing loss.
A new look at dementia prevention
“I was less surprised by the differences and more surprised by some of the similarities, particularly in the ways these risks are patterned across settings,” Nichols said.
The clustering hints that the biology and habits behind these risks may run deeper than the country-by-country differences imply.
That consistency has a practical advantage. Instead of tackling each risk factor separately, countries could design prevention programs that address entire clusters of related risks.
High cholesterol and high blood pressure, for example, are best treated as the linked problem they usually represent.
Dementia risk isn’t pre-determined
The stakes climb with every passing year. Worldwide, the number of adults living with dementia is projected to nearly triple by 2050, according to one analysis.
Cases are expected to rise from about 57 million to more than 150 million, with the steepest growth expected in lower-income regions.
Those are exactly the places this study reached that earlier work had missed. Local numbers change the math.
Knowing which risks dominate in China, India, or Brazil lets health officials aim limited resources where they will do the most good. That beats importing a plan built for somewhere else.
For an individual, the findings carry an encouraging edge. “Risk for these late-life outcomes isn’t predetermined,” said Nichols.
She noted that people can influence their own risk even as broader social forces press on it.
The future of dementia prevention
Other scientists want the list itself to grow. A recent paper argued that poverty, income inequality, and sudden losses of wealth belong among the tracked risks in poorer countries.
There, these factors weigh on health as heavily as blood pressure or diet.
The USC team is already extending the work, adding newer risks such as poor sleep and folding in fresh data from Kenya and Egypt.
What the study has settled is that the map of dementia risk is genuinely local, even as the deeper patterns beneath it repeat across borders.
Prevention that respects both truths, tailored to each population yet built on the shared clusters, now has the evidence to proceed.
The study is published in The Lancet Healthy Longevity.
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