The top three modifiable factors that increase your risk of dementia

Certain lifestyle factors can influence dementia risk, and a new study highlights the top threats to Americans today: obesity, physical inactivity and lack of a high school diploma.

The researchers found that in the last decade alone there has been a shift in the most important modifiable risk factors for dementia in the United States. In 2011, the big three were physical inactivity, depression and smoking.

Today, lack of exercise is still in the top three, but the other points have been replaced by obesity in middle-aged people and low levels of education (no high school diploma) .

At the same time, the study found that the first three are not identical: the main modifiable risk factors for dementia vary somewhat by race and ethnicity.

Obesity was the No. 1 factor among white, black and Native American adults, while lack of exercise was the top threat for Asian Americans. Among Hispanic Americans, low education emerged as the main modifiable risk factor.

“Our results suggest that people may be able to reduce their risk of developing Alzheimer’s disease and [other types of] dementia by adopting a healthy lifestyle,” said researcher Deborah Barnes, a professor of psychiatry at the University of California, San Francisco.

The greatest risk factor for Alzheimer’s disease and other forms of dementia is advancing age, which obviously people cannot change. Genetic susceptibility is another major player; people who carry a gene variant called APOE4, for example, have a higher likelihood of developing Alzheimer’s disease than non-carriers.

But it’s estimated that around 40% of dementia cases worldwide can be attributed to modifiable risk factors, said Rebecca Edelmayer, senior director of science engagement for the Alzheimer’s Association.

These include the top three found in this study, as well as factors such as high blood pressure, diabetes, excessive alcohol consumption and hearing loss.

The reasons for these links are not entirely clear, said Edelmayer, who was not involved in the new research. But cardiovascular health is seen as a pathway. Obesity, high blood pressure, diabetes, smoking, and a sedentary lifestyle can all damage the blood vessels that supply not only the heart, but also the brain.

“The strongest data we have suggests that what’s good for your heart is good for your brain,” Edelmayer said.

As for education, the researchers believe this may help via what’s called the “cognitive reserve hypothesis”: more educated people may be better equipped to resist the pathological brain changes seen in dementia and maintain their memory and thinking skills longer.

The current results were published May 9 in JAMA Neurology. They are based on more than 378,000 American adults who participated in an annual government health survey.

Overall, researchers estimate that 37% of dementia cases nationwide are linked to one of eight modifiable risk factors: midlife obesity, inactivity, low education, depression, hypertension blood pressure, diabetes, smoking and hearing loss.

One reason, Barnes said, is sheer prevalence. Obesity has become much more common over the past decade, so it contributes to more cases of dementia.

Meanwhile, she says, recent studies have suggested that the link between low levels of education and dementia is stronger than previously thought. Researchers therefore believe that this factor contributes to more cases of dementia among Americans.

But the relative importance of these factors among different groups of Americans differs. Along with observed differences between racial/ethnic groups, males and females showed some variance. Modifiable risk factors played a greater role in dementia risk in men, with 36% of cases linked to these factors, compared to 30% in women.

Depression was also a greater contributing factor in women than in men. In women, nearly 11% of dementia cases could be linked to a lifetime history of depression, according to co-investigator Dr. Roch Nianogo, of the University of California, Los Angeles School of Public Health.

Nearly a quarter of the women in the study said they had been diagnosed with depression at some point.

Edelmayer said the research is now moving beyond finding associations to testing ways to reduce the risk of dementia.

“We believe adopting a combination of healthy behaviors may be more effective,” Edelmayer said.

The Alzheimer’s Association is funding a trial called US POINTER, which is testing this combination approach in older people at increased risk of dementia. Lifestyle measures include exercise, mentally stimulating activities, and better control of high blood pressure and diabetes.

It’s critical, Edelmayer said, that studies recruit people of color, who have historically been underrepresented in medical research. As this study shows, she noted, the major modifiable risk factors for dementia vary among different groups of Americans.

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