A new USC-led study of more than 214,000 older adults in 14 countries and territories suggests that different strategies may be needed in different parts of the world to prevent dementia. Researchers found that many of the most important modifiable dementia risk factors, such as low education, high blood pressure, and smoking, varied widely across countries. The findings indicate that a single global approach to dementia prevention is unlikely to be effective everywhere.
The research was presented at the Alzheimer’s Disease Association International Conference 2026 in London and published in a journal. Lancet Health and Longevity. AAIC is the world’s largest academic conference focused on dementia research.
Dementia risk factors vary around the world
Most existing research on dementia prevention has been conducted in high-income countries such as the United States and Western European countries. To determine whether these findings apply more broadly, USC researchers collaborated with colleagues at Brown University and Johns Hopkins University to examine data from both high-income and low- and middle-income countries.
The results revealed significant differences, along with some unexpected similarities.
For example, low educational attainment affects 85.6% of older adults in China, but only 12.0% in the United States. Meanwhile, high BMI (a measure of excess weight) was found in 44.9% of Americans, compared to just 13.3% in India.
Although individual risk factors vary from country to country, many of them appear in similar combinations around the world. Cardiovascular diseases such as high cholesterol and hypertension often co-occurred, and behaviors such as smoking and drinking also tended to occur in groups.
Lead author Emma Nichols, a research fellow at the Center for Economic and Social Research at the University of Southern California’s Schaefer Institute for Public Policy and Government Services, said these common patterns were one of the study’s biggest surprises.
“I wasn’t really surprised by the differences, but I was even more surprised by some of the similarities, particularly how these risks are patterned across environments,” Nichols said. “This has major implications for how we design prevention strategies and interventions, because some things are more consistent across locations than we would expect.”
Click here to see a diagram showing the differences and similarities in dementia risk across countries.
Analyzed over 214,000 seniors
The research team used harmonized survey data collected between 2009 and 2023 through the Gateway to Global Aging Data project. This dataset combines information from longitudinal aging studies in 14 locations, including the United States, United Kingdom, Ireland, Northern Ireland, four regions of Europe, South Korea, Mexico, China, Malaysia, Brazil, and India. (Jin-kook Lee of the USC Schaefer Institute’s Center for Economic and Social Research is the principal investigator of the Gateway to Global Aging Data Project and the Longitudinal Aging Study in India.)
Researchers looked at 12 modifiable dementia risk factors identified by the Lancet Commission on Dementia, including hearing loss, depression, physical inactivity and social isolation. They measured how common each risk factor is, how it varies by age, gender, and education level, and how often multiple risk factors occur together in the same individual.
Customize dementia prevention
Researchers say the findings could help governments and health organizations tailor prevention programs to the needs of their populations.
For example, programs that help manage diabetes can also be expanded to address associated cardiometabolic risks, such as high cholesterol and hypertension, allowing multiple related health issues to be addressed together.
Nichols emphasized that the results also contain an encouraging message for individuals.
“The risk of these late-life outcomes is not predetermined. These are risk factors that we experience throughout our lives, and we can influence to change our own risk, while also being aware of the ways in which wider social factors shape that risk.”
Future studies may investigate additional modifiable risk factors such as sleep deprivation, expanding the study to more countries as comparable datasets become available. Data collection is already underway in other countries, including Kenya and Egypt.
About research
The study was led by Emma Nichols of the USC Schaefer Institute’s Center for Economic and Social Research. Additional authors include senior authors Jinkook Lee, Michael Markot, Drystan Phillips, and Jenny Wilkens from the Gateway to Global Aging Data team. Co-author Zachary Kunicki of the Warren Alpert School of Medicine at Brown University. Alden Gross of the Johns Hopkins Bloomberg School of Public Health.
This research was supported by the National Institutes of Health (grant R01AG030153).
