The prevalence of dementia risk factors varies widely between countries, but the way these risks cluster together is remarkably similar across the world, according to a new study published in The Lancet Healthy Longevity.

The international study found that although high-income and low- and middle-income countries differ in the frequency of individual dementia risk factors, more than half of adults aged 50 years and above had at least two established risk factors for dementia, highlighting the global need for preventive strategies.

Researchers led by Dr. Emma Nichols from the University of Southern California analysed harmonised data from 214,251 adults aged 50 years and older across 14 countries and regions. The analysis combined findings from 11 nationally representative ageing studies to compare the prevalence and patterns of 12 well-established dementia risk factors.

The study revealed notable differences between high-income countries (HICs) and low- and middle-income countries (LMICs). Low educational attainment was far more common in many LMICs, affecting 85.6% of participants in China compared with 12% in the United States. In contrast, obesity was much more prevalent in high-income countries, with 44.9% of participants in the United States classified as obese compared with 13.3% in India.

Researchers also found that the distribution of dementia risk factors differed according to age, gender and educational status, although these patterns were not consistent across all countries.

Despite these differences, one finding stood out. Across every country and region studied, dementia risk factors frequently occurred together. More than half of the participants had at least two risk factors, and similar clusters emerged across populations. These clusters were mainly linked to cardiovascular diseases, unhealthy lifestyle behaviours, and social or sensory factors.

Dr. Nichols said she was struck not so much by the differences between countries but by the similarities in how dementia risk factors grouped together across diverse populations. She noted that these shared patterns could help guide global strategies aimed at reducing dementia risk through targeted prevention and public health interventions.

The findings suggest that while countries may need tailored approaches to address their most common risk factors, many of the underlying combinations of risks are shared worldwide, offering opportunities for coordinated efforts to prevent dementia.