A large new study is challenging a basic assumption behind most dementia prevention advice: that the same risk factors matter roughly the same amount everywhere. They don’t, according to researchers, and that has real implications for how prevention programs get designed around the world.
The study, led by researchers at the University of Southern California along with colleagues at Brown University and Johns Hopkins University, analyzed data from more than 214,000 older adults across 14 countries and regions, including the United States, England, China, Brazil, and India. The findings were presented at the Alzheimer’s Association International Conference in London and published in the journal The Lancet Healthy Longevity.
Most existing research on dementia prevention comes from wealthy countries, mainly the United States and Western Europe. This study set out to check whether the same risk factors carry the same weight in lower and middle income countries, using survey data collected between 2009 and 2023 from long-running aging studies in each location.
They didn’t. The differences were substantial. Low education affected 85.6% of older adults in China but only 12% in the United States. High BMI, a marker for obesity, showed up in 45% of Americans but only 13% of adults in India. Researchers looked at 12 modifiable risk factors identified by the Lancet Commission on dementia, including hearing loss, depression, physical inactivity, social isolation, high blood pressure, and smoking, and found this same pattern of sharp variation across most of them.
There was an important similarity buried inside all that difference, though. Across every country and region studied, more than half of individuals had at least two risk factors at the same time, and those risk factors tended to cluster into similar groups everywhere: cardiovascular-related factors like blood pressure and cholesterol, risky-behavior factors like smoking and inactivity, and social or sensory factors like isolation and hearing loss. The specific mix varies by country. The tendency for risk factors to travel in packs does not.
That clustering pattern has a practical upside researchers pointed to directly. A program built to connect people with diabetes care, for instance, could be redesigned to address an entire cluster of related cardiometabolic risks, cholesterol and blood pressure included, in the same visit, rather than treating each condition as a separate problem needing its own separate outreach effort.
The bigger takeaway is what this means for prevention strategy going forward. A campaign built around America’s most common risk factors, obesity and inactivity, would largely miss the mark in a country where low education and untreated hearing loss are doing most of the damage. Effective prevention, according to the researchers, has to start with knowing which risk factors are actually most common in a given population, not assuming the pattern seen in one wealthy country applies everywhere else.
The study isn’t without real limits, and the researchers were direct about them. Physical inactivity is measured differently across economies, since some surveys capture occupational activity and others only leisure activity, which limits clean comparison. The 12-factor framework used here reflects the Lancet Commission’s 2020 list and doesn’t yet include two factors added in a 2024 update, vision loss and high LDL cholesterol. Poor sleep, an increasingly studied risk factor in its own right, wasn’t included at all. And sub-Saharan Africa and North Africa aren’t represented in this analysis, though data collection is already underway in Kenya and Egypt for future research.
For families thinking about dementia risk across generations, particularly those with relatives who immigrated from a different country or grew up under very different conditions, this research is a reminder that prevention advice built around headlines from Western studies doesn’t automatically transfer. What actually reduces risk may depend heavily on where a person spent their life, not just their age today.
