Dementia affects millions of families around the world and is becoming more common as people live longer. The condition slowly damages memory, thinking and the ability to carry out everyday tasks.
Although there is still no cure, many studies show that healthy lifestyle choices and good medical care may lower the risk of developing dementia.
Scientists are therefore trying to learn which risk factors matter most and whether they are the same in every country.
A large international study led by the University of Southern California has found that the answer is no. The research was presented at the Alzheimer’s Association International Conference 2026 in London and was also published in The Lancet Healthy Longevity.
The findings suggest that each country may need its own plan for reducing dementia risk instead of relying on a single global approach.
The researchers analysed information from more than 214,000 older adults living in 14 countries and regions. The data came from long-running ageing studies collected between 2009 and 2023. By combining these studies, the scientists were able to compare populations using the same methods.
They focused on 12 risk factors that can potentially be changed during life. These included high blood pressure, smoking, hearing loss, depression, physical inactivity, social isolation, diabetes and low education. Unlike age or family history, these are factors that people or health systems may be able to improve.
The results showed striking differences between countries. Low education affected more than 85% of older adults in China but only about 12% in the United States. High body weight was much more common in the United States than in India, showing that health challenges differ greatly from one nation to another.
Despite these differences, the researchers also found important similarities. High blood pressure and high cholesterol often appeared together. Smoking and drinking also commonly occurred in the same people regardless of where they lived.
Lead author Emma Nichols said these shared patterns were one of the study’s biggest surprises. They suggest that some prevention programs could target several linked health problems at the same time instead of treating each one separately.
The findings could help governments spend healthcare resources more effectively. For example, clinics that already help patients control diabetes might also provide support for blood pressure, cholesterol and healthy lifestyles. This could improve overall brain and heart health together.
The researchers also stressed that individuals are not powerless. Looking after blood pressure, staying active, avoiding smoking, remaining socially connected and continuing to learn throughout life may all help lower dementia risk. Future research will include more countries, including Kenya and Egypt, and may also study factors such as poor sleep.
This study is important because it moves dementia research beyond wealthy countries and provides a broader picture of global ageing. However, it does not prove that every risk factor directly causes dementia, because it mainly compares patterns across populations.
Even so, the work offers valuable guidance for future public health planning and supports the idea that prevention strategies should be adapted to local needs while encouraging healthy habits everywhere.
If you care about dementia, please read studies that eating apples and tea could keep dementia at bay, and Olive oil: a daily dose for better brain health.
For more health information, please see recent studies what you eat together may affect your dementia risk, and time-restricted eating: a simple way to fight aging and cancer.
