Health
Dementia Risk Factors Vary Dramatically from Country to Country — Why Prevention Cannot Be One-Size-Fits-All
A landmark USC-led study of more than 214,000 older adults across 14 countries reveals that the most important modifiable dementia risk factors — low education, high blood pressure, smoking — differ so widely between nations that a universal prevention strategy is unlikely to work everywhere.
- Modifiable dementia risk factors — low education, hypertension, smoking, hearing loss — vary dramatically in importance from country to country.
- The USC-led harmonized study of 214,000 older adults across 14 nations found that population-level prevention strategies cannot be applied uniformly worldwide.
- In high-income countries, hypertension and inactivity dominate risk; in lower-income settings, low education and hearing loss are the bigger contributors.
For decades, public health campaigns around the world have promoted essentially the same message about dementia prevention: stay physically active, keep your blood pressure under control, don't smoke, and stay mentally engaged. A major new study published in The Lancet Healthy Longevity suggests this one-size-fits-all approach may be fundamentally misguided — because the risk factors that matter most depend heavily on where you live.
Led by researchers at the University of Southern California (USC) in collaboration with Brown University and Johns Hopkins University, the study analyzed harmonized data from more than 214,000 older adults across 14 countries and regions, including the United States, England, China, India, Brazil, South Africa, and several European nations. It is one of the largest cross-national comparisons of modifiable dementia risk factors ever conducted.
The findings were striking. In the United States and other high-income countries, hypertension and physical inactivity were the dominant contributors to dementia risk. In China and India, low education was the most powerful predictor, reflecting disparities in early-life access to schooling. In several Latin American and African cohorts, hearing loss and smoking emerged as leading factors. Even within similar economic brackets, the pattern of risk varied substantially, suggesting that cultural, environmental, and genetic factors all play a role.
Forty-five percent of dementia cases worldwide are estimated to be attributable to 14 modifiable risk factors, according to the 2024 Lancet Commission. But the new USC-led study shows that the relative importance of each factor is not uniform. For example, while hypertension is a major risk in high-income countries, its population-attributable fraction was far lower in several middle-income countries where low education dominated instead.
The study's authors argue that dementia prevention strategies must be tailored to local profiles. A campaign that works in the United Kingdom — where physical inactivity is a top concern — may have limited impact in rural India, where improving access to primary education could yield greater brain-health benefits. The findings also highlight the need for better data from understudied regions, especially Africa and the Middle East, where dementia rates are expected to rise sharply in coming decades.