Dementia risk factors vary widely by country, study finds

The modifiable risk factors that contribute to dementia differ markedly from country to country, underscoring the need for prevention strategies tailored to each nation's specific conditions, a new study has found.

In South Korea, less than a secondary-school education emerged as the most common modifiable dementia risk factor, while in the United States, high blood pressure, smoking and high cholesterol topped the list. By contrast, low educational attainment ranked 11th in the US.

A research team led by Dr. Emma Nichols of the University of Southern California presented the findings Monday at the Alzheimer's Association International Conference (AAIC 2026) in London. The study was also published in the journal Lancet Healthy Longevity.

The researchers said the prevalence of dementia risk factors — including education level, high blood pressure and smoking — varies so significantly across countries that applying a single uniform prevention strategy worldwide may have its limits.

They also said that because most existing dementia research has been conducted in high-income countries such as the United States and Western Europe, it has not been sufficiently verified whether those findings can be appropriately applied to low- and middle-income countries.

The team pooled and analyzed data covering more than 214,000 older adults across 14 countries and regions — including the United States, the United Kingdom, Ireland, four European subregions, South Korea, China, India, Malaysia, Brazil and Mexico — collected between 2009 and 2023.

The analysis drew on 12 modifiable dementia risk factors identified by the Lancet Commission on Dementia, including education level, high blood pressure, smoking, physical inactivity, vision impairment, high cholesterol, obesity, depression, hearing loss, social isolation, diabetes and excessive alcohol consumption.

The rankings of risk factors differed substantially by country.

The starkest variation involved less than a secondary-school education. It was the most common modifiable dementia risk factor in South Korea, China, India, Malaysia, Brazil and Mexico, yet ranked 11th — among the lowest — in the United States.

Conversely, overweight and obesity ranked as the fourth most common risk factor in the US but fell to 10th in South Korea and ninth in China.

South Korea's top five modifiable dementia risk factors were, in order: less than a secondary-school education, high blood pressure, smoking, depression and vision impairment. The US top five were high blood pressure, smoking, high cholesterol, obesity and physical inactivity.

In the United Kingdom, Western Europe and the Nordic countries, smoking was the most prevalent risk factor. Eastern Europe showed a distinct pattern — high blood pressure ranked first and smoking second.

The research team also identified common patterns that cut across national differences. Cardiovascular risk factors such as high blood pressure and high cholesterol frequently appeared together, and health-harming behaviors such as smoking and heavy drinking tended to co-occur in most countries as well.

"What surprised me more than the differences between countries was how similarly the risk factors clustered together across different settings," Nichols said. "That has important implications for designing prevention strategies that address interconnected risk factors while still reflecting each country's specific context."

She added that dementia risk is not fixed at birth but is shaped by a lifetime of exposure to various risk factors, making it important to improve not only lifestyle habits but also social conditions — including access to education and healthcare.

Experts say the study demonstrates that dementia prevention policy must account for each country's health environment alongside its social and educational conditions. Rather than targeting a single risk factor in isolation, an integrated approach — combining expanded access to education, chronic disease management and smoking cessation programs — could improve the effectiveness of dementia prevention efforts.