A monumental international investigation, spearheaded by researchers at the University of Southern California (USC) and encompassing data from over 214,000 older adults across 14 diverse nations and regions, has revealed a compelling truth: the landscape of dementia risk is far from uniform, suggesting that a one-size-fits-all global approach to prevention is unlikely to yield optimal results. The study’s findings, presented at the prestigious Alzheimer’s Association International Conference (AAIC) 2026 in London and subsequently published in the esteemed journal The Lancet Healthy Longevity, illuminate significant variations in the prevalence and clustering of modifiable risk factors for dementia across different cultural and socioeconomic contexts.
For decades, the bulk of research concerning dementia prevention has been predominantly conducted in high-income nations, such as the United States and various Western European countries. This new, expansive study aimed to bridge that gap by meticulously examining data from both high-income and low-to-middle-income countries, fostering a more comprehensive understanding of dementia’s global epidemiology. The collaborative effort involved USC alongside esteemed colleagues from Brown University and Johns Hopkins University, pooling their expertise to analyze a vast dataset that paints a nuanced picture of risk.
The investigation unearthed striking disparities in the commonality of specific risk factors. For instance, the burden of low educational attainment, a known contributor to cognitive decline, was profoundly different across surveyed populations. In China, a staggering 85.6% of older adults reported low education levels, starkly contrasting with the 12.0% observed in the United States. Conversely, the prevalence of high Body Mass Index (BMI), an indicator of excess body weight often linked to cardiovascular issues, was notably higher among Americans, affecting 44.9% of the population, compared to just 13.3% in India. These figures underscore the profound impact of socioeconomic development and lifestyle factors on individual health profiles within a global context.
However, the research also highlighted unexpected consistencies. Despite the pronounced differences in individual risk factor prevalence, the study observed that many of these factors often co-occurred in similar patterns worldwide. Cardiovascular concerns, such as elevated cholesterol levels and hypertension, frequently presented as a cluster of interconnected issues. Similarly, behavioral risk factors, including smoking and alcohol consumption, tended to manifest together within individuals, suggesting underlying lifestyle patterns that transcend geographical boundaries. This clustering of risks is a critical insight, as it implies that interventions targeting one factor might inadvertently address others, offering a more efficient pathway to risk reduction.
Emma Nichols, the lead author of the study and a research scientist at the USC Schaeffer Institute for Public Policy & Government Service’s Center for Economic and Social Research, expressed surprise at the consistency of these risk factor patterns across diverse settings. "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 stated. "That has real implications for how we design prevention strategies and interventions, because some things are more consistent across places than we might expect." This observation is crucial for informing policy and public health initiatives, suggesting that while a globally standardized approach may be ineffective, certain interconnected risk profiles might lend themselves to universally applicable intervention frameworks.
The robust dataset underpinning this research was meticulously compiled between 2009 and 2023, drawing from harmonized survey data collected through the comprehensive Gateway to Global Aging Data project. This project aggregates information from long-running longitudinal aging studies conducted in 14 distinct locations. These included the United States, England, Ireland, Northern Ireland, four distinct regions within Europe, South Korea, Mexico, China, Malaysia, Brazil, and India. The breadth of this data collection is unparalleled, providing a rich foundation for cross-cultural comparisons. Jinkook Lee, the principal investigator of the Gateway to Global Aging Data project and the Longitudinal Aging Study in India, based at the USC Schaeffer Institute, played a pivotal role in assembling this invaluable resource.
The research team systematically examined 12 modifiable dementia risk factors, as previously identified by the influential Lancet Commission on dementia. These included factors such as hearing loss, depression, physical inactivity, and social isolation. The study meticulously quantified the prevalence of each risk factor, analyzed its variation across different age groups, genders, and educational strata, and investigated the frequency with which multiple risk factors coexisted within the same individual. This granular approach allows for a detailed understanding of how these factors interact and contribute to overall risk.
The implications of these findings are profound for public health policy and governmental planning. The researchers suggest that their results can empower governments and health organizations to develop and implement dementia prevention programs that are far more finely tuned to the specific needs and characteristics of their respective populations. For instance, a public health initiative designed to assist individuals in managing diabetes could be strategically expanded to simultaneously address related cardiometabolic risks, such as high cholesterol and hypertension. This integrated approach allows for the efficient management of multiple, interconnected health issues, maximizing the impact of public health interventions.
Nichols further emphasized that the study carries an encouraging and empowering message for individuals, underscoring the agency people have in managing their own health trajectories. "Risk for these late-life outcomes isn’t predetermined," she asserted. "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." This dual perspective—acknowledging both individual responsibility and the influence of societal determinants—is essential for effective health promotion.
Looking ahead, the research team plans to expand their scope, investigating additional modifiable risk factors such as poor sleep, and extending their data collection to an even wider array of countries as comparable datasets become available. Preliminary data collection is already underway in new regions, including Kenya and Egypt, promising further insights into the global landscape of dementia risk. The continued expansion of this research effort is vital for building a comprehensive, evidence-based global strategy for dementia prevention.
The foundational work for this significant study was led by Emma Nichols of the USC Schaeffer Institute’s Center for Economic and Social Research. Key contributions were also made by senior author Jinkook Lee and team members Michael Markot, Drystan Phillips, and Jenny Wilkens from the Gateway to Global Aging Data team. Co-first author Zachary Kunicki from the Warren Alpert Medical School of Brown University and Alden Gross from the Johns Hopkins Bloomberg School of Public Health were also instrumental in the research. The project received vital financial support from the National Institutes of Health under grant R01AG030153, facilitating this groundbreaking international collaboration.
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