A large international study led by USC has found that the most common preventable or manageable risk factors for dementia differ sharply around the world. The analysis included more than 214,000 older adults from 14 countries and regions and examined factors such as limited education, high blood pressure, and smoking.

The results suggest that dementia prevention cannot rely on the same strategy everywhere. The risks that affect the greatest number of people in one country may be far less common in another.

The findings were presented at the Alzheimer’s Association International Conference 2026 in London and published in The Lancet Healthy Longevity. AAIC is the largest international gathering devoted to dementia research.

Expanding Dementia Research Beyond Wealthy Countries

Much of the existing evidence about dementia prevention comes from studies conducted in wealthier nations, particularly the United States and countries in Western Europe. Researchers from USC, Brown University, and Johns Hopkins University wanted to determine whether the same risk patterns also appear in low- and middle-income countries.

Their analysis uncovered major differences between populations, along with some unexpected similarities.

Low education affected 85.6% of older adults in China, compared with only 12.0% in the United States. High BMI (a measure of excess body weight), by contrast, was found in 44.9% of participants in the United States but only 13.3% of those in India.

Despite these differences, certain risks frequently appeared together in similar combinations across the world. Cardiovascular problems, including high cholesterol and hypertension, often formed one cluster. Behaviors such as smoking and drinking commonly formed another.

Similar Risk Patterns Across Different Populations

Lead author Emma Nichols, a research scientist with the Center for Economic and Social Research at the USC Schaeffer Institute for Public Policy & Government Service, said these shared patterns were among the study’s most surprising results.

“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. “That has real implications for how we design prevention strategies and interventions, because some things are more consistent across places than we might expect.”

Click here for a graphic depicting differences and similarities in dementia risk across different countries.

Data From More Than 214,000 Older Adults

Researchers with the Gateway to Global Aging Data team brought together standardized survey information from long-running aging studies in 14 locations. These included the United States, England, Ireland, Northern Ireland, four regions of Europe, Korea, Mexico, China, Malaysia, Brazil, and India. The data were collected between 2009 and 2023. (Jinkook Lee of the Center for Economic and Social Research at the USC Schaeffer Institute is principal investigator of the Gateway to Global Aging Data project as well as the Longitudinal Aging Study in India.)

The team examined 12 modifiable dementia risk factors identified by the Lancet Commission on dementia. Modifiable risk factors are conditions or behaviors that may be changed or managed over time. The factors included hearing loss, depression, physical inactivity, and social isolation.

Researchers compared how frequently each risk appeared, how prevalence differed according to age, gender, and education, and how often several risks occurred in the same person.

Why Dementia Prevention Must Be Tailored

The findings could help governments, health systems, and other organizations create prevention programs that better match the needs of their populations.

For instance, a program designed to connect people with diabetes care could be expanded to address a broader group of related cardiometabolic risks, including hypertension and high cholesterol. Targeting several connected risks together may be more effective than treating each one separately.

The research also carries an encouraging message for individuals. Dementia risk is not necessarily fixed, and many contributing factors can be influenced throughout life.

“Risk for these late-life outcomes isn’t predetermined. These are risk factors you experience over the life course, and you can have an impact on changing your own risk — while also recognizing the ways broader societal factors shape that risk, too.”

Future Research Will Include More Countries

Future studies may examine newer potential risk factors, including poor sleep. Researchers also plan to add more countries as additional standardized data become available.

New data collection is already taking place in Kenya and Egypt, which could provide an even broader picture of how dementia risks differ and overlap across populations.