Worldwide Study Finds Dementia Risks Differ Across Countries, Including India

India's fight against dementia may require a strategy distinct from those adopted in high-income countries, with new global research showing that the pattern of modifiable risk factors varies substantially across populations. While cardiovascular risks and unhealthy lifestyle behaviours tend to cluster similarly across nations, factors such as obesity, education and social conditions differ widely, underscoring the need for country-specific prevention programmes.

The findings come from one of the largest cross-national analyses of dementia risk factors to date, involving more than 214,000 older adults across 14 countries and regions, including India.

The study, led by researchers at the University of Southern California (USC) in collaboration with Brown University and Johns Hopkins University, was presented at the Alzheimer's Association International Conference (AAIC) 2026 in London. It is published in The Lancet Healthy Longevity.

The researchers had examined 12 modifiable risk factors for dementia identified by the Lancet Commission, including hypertension, diabetes, obesity, smoking, alcohol use, hearing loss, depression, physical inactivity, social isolation and low educational attainment.

For India, one of the most striking observations was the comparatively low prevalence of obesity among older adults. Only 13.3 per cent of older adults in India had a high Body Mass Index (BMI), compared with 44.9 per cent in the United States. The finding suggests that while obesity remains an emerging public health concern in India, it may currently play a relatively smaller role in dementia risk compared to several Western countries.

However, experts caution that this should not lead to complacency. India is simultaneously witnessing rapid urbanisation, sedentary lifestyles and a growing burden of diabetes, hypertension and cardiovascular diseases—conditions already known to increase dementia risk.

The study found that although the prevalence of individual risk factors differed sharply across countries, the way these risks combined within individuals remained remarkably similar. Cardiometabolic conditions such as hypertension, diabetes and high cholesterol frequently occurred together, while smoking and alcohol consumption formed another common behavioural cluster.

Lead author Emma Nichols, a research scientist at the Center for Economic and Social Research at the USC Schaeffer Institute for Public Policy & Government Service, said the similarities were perhaps more revealing than the differences.

"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."

The researchers believe that recognising these clusters could help governments design more efficient prevention programmes. Instead of addressing hypertension, diabetes or high cholesterol individually, health systems could integrate screening and management of multiple cardiometabolic risks under a single preventive framework.

The analysis was based on harmonised data collected between 2009 and 2023 through long-running ageing studies conducted in the United States, England, Ireland, Northern Ireland, four European regions, South Korea, Mexico, China, Malaysia, Brazil and India. India's data came from the Longitudinal Ageing Study in India (LASI), one of the world's largest surveys on ageing.

Unlike many earlier studies that primarily relied on populations from Europe and North America, this research also included low- and middle-income countries to determine whether established dementia risk profiles remained applicable globally.

The answer, researchers found, was both yes and no.

For example, low educational attainment affected 85.6 per cent of older adults in China but only 12 per cent in the United States. Such disparities illustrate how social determinants can influence dementia risk differently across countries.

India occupies a unique position in this spectrum, as per the study. While educational access has expanded dramatically over the past few decades, many of today's elderly population grew up with limited schooling, particularly women and those in rural areas.

Previous Indian studies have consistently linked lower educational attainment with poorer cognitive reserve, increasing susceptibility to dementia in later life.

At the same time, India is undergoing an epidemiological transition. Improved life expectancy has resulted in a rapidly growing elderly population, bringing age-related neurological disorders into sharper public health focus.

According to Alzheimer's Disease International, the number of people living with dementia in India is expected to rise substantially over the coming decades as the population ages.

Health experts note that the country's dementia burden is further complicated by high rates of uncontrolled hypertension, diabetes and stroke, alongside inadequate awareness, delayed diagnosis and limited specialised geriatric care.

The new findings suggest that India may benefit from integrating dementia prevention into existing non-communicable disease (NCD) programmes. Routine screening for blood pressure, diabetes and cholesterol at primary healthcare centres could simultaneously contribute to reducing future dementia risk, particularly if accompanied by lifestyle counselling, smoking cessation and physical activity promotion, the study indicates.

Nichols said that individuals still have considerable control over their future brain health.

"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."

Researchers said future analyses will incorporate emerging risk factors such as poor sleep and include additional countries as harmonised ageing data become available. New longitudinal data collection has already begun in countries including Kenya and Egypt.