These three risk factors may have the biggest impact on dementia cases

Nearly half of all dementia cases in the U.S. may be linked to a dozen modifiable risk factors – most notably high blood pressure, obesity and physical inactivity, according to new research. The findings suggest a large portion of dementia cases could be prevented, especially among Black and Hispanic adults, who had the highest percentage of combined risk factors.

"There are things people can do that can raise or lower their individual risk" for dementia, said Mark Lee, a PhD candidate at the University of Minnesota in Minneapolis. He led the study presented Friday at the American Heart Association's Epidemiology and Prevention, Lifestyle and Cardiometabolic Health conference.

As the population ages, the number of dementia cases in the U.S. has been climbing. Currently about 5.8 million U.S. adults live with Alzheimer's disease and related dementias, according to the Centers for Disease Control and Prevention. That number is expected to hit 14 million by 2060, with Black and Hispanic adults seeing the largest increases. Among Hispanic adults, cases are expected to rise sevenfold, while cases among aging Black adults are expected to quadruple.

Those higher rates among Black and Hispanic people may be due to higher rates of heart disease and diabetes, which are linked to dementia risk. Social determinants of health – such as lower levels of education, higher rates of poverty and greater exposure to discrimination – also play a role.

Previous research identified 12 modifiable risk factors believed to be responsible for roughly 40% of dementia cases worldwide. A 2020 report by the Lancet Commission listed these as lower education level, hearing loss, traumatic brain injury, high blood pressure, excessive alcohol consumption, obesity, smoking, depression, social isolation, not getting the recommended amount of physical activity, diabetes and air pollution.

In the new study, researchers wanted to know if some risk factors had a greater influence than others on dementia rates – and how that differed among Black, Hispanic, Asian and white adults. They compiled data from the CDC's National Health and Nutrition Examination Survey and five other datasets.

Overall, 42.4% of dementia cases in the U.S. were attributable to the 12 factors, with three heart-related factors driving the bulk of that risk across races. High blood pressure, also known as hypertension, contributed to 6.7% of those cases; obesity to 7%; and physical inactivity to 6.7%.

The percentage of dementia cases attributable to those three risk factors was highest among Black adults. But the percentage of all 12 risk factors combined was highest among Hispanic people. Asian people had the lowest percentage of combined risk factors.

The results are considered preliminary until a full paper is published in a peer-reviewed journal.

The findings, Lee said, point to the need for better strategies to reduce heart-related risk factors, which would in turn reduce dementia risk population-wide.

This can, in part, be done through lifestyle changes, combined with medication as needed, said Priya Palta, an assistant professor of medical sciences and epidemiology at Columbia University Irving Medical Center in New York City.

"Maintaining a cognitively and physically active lifestyle and controlling risk factor levels pharmacologically, when necessary, throughout one's life course is critical for later-life brain health and is likely to impact many of the risk factors examined in this study," said Palta, who was not involved in the research.

Lee said the next step is to determine which interventions are most effective for reducing each of the 12 modifiable dementia risk factors. He also said a deeper investigation is needed into the social determinants of health underlying racial disparities, such as the disproportionately high rate of hypertension among Black adults.

"That's a really important direction we need to move to if we are serious about achieving equity in health interventions."

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