Certain lifestyle factors can sway the risk of dementia, and a new study points to the top threats to Americans these days: obesity, physical inactivity and lack of a high school diploma.
Researchers found that in just the past decade, 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Today, lack of exercise is still among the top three, but the other spots have been replaced by obesity in middle-age and low education levels (not graduating from high school).
Risk factors vary according to race dementia
At the same time, the study found, that the top three are not one-size-fits-all: The leading modifiable risk factors for dementia vary somewhat according to race and ethnicity.
Obesity was the No. 1 factor among white, Black and Native American adults, while lack of exercise was the top threat to Asian Americans. Among Hispanic Americans, meanwhile, low educational attainment emerged as the top modifiable risk factor.
"Our results suggest that people may be able to reduce their risk of developing Alzheimer's and [other types of] dementia by engaging in a healthy lifestyle," says researcher Deborah Barnes, a professor of psychiatry at the University of California, San Francisco.
The biggest risk factor for Alzheimer's and other forms of dementia is older age, which people obviously 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 than non-carriers do.
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Modifiable risk factors
But it's been estimated that about 40% of dementia cases worldwide can be attributed to modifiable risk factors, says Rebecca Edelmayer, senior director of scientific engagement for the Alzheimer's Association.
Those include the top three found in this study, plus factors such as high blood pressure, diabetes, heavy drinking and hearing loss.
The reasons for those links are not fully clear, says Edelmayer, who was not involved in the new research. But cardiovascular health is thought to be one pathway. Obesity, high blood pressure, diabetes, smoking and a sedentary lifestyle can all damage blood vessels that feed not only the heart, but the brain.
"The strongest data we have suggest that what's good for your heart is good for your brain," Edelmayer adds.
As for education, researchers think that may help via what's called the "cognitive reserve" hypothesis: People with more education may be better equipped to withstand the pathological brain changes seen in dementia, and maintain their memory and thinking abilities for a longer time.
The current findings are based on more than 378,000 U.S. adults who took part in an annual government health survey.
Overall, the researchers estimate, 37% of dementia cases nationally are linked to any of eight modifiable risk factors: midlife obesity, inactivity, lower educational attainment, depression, high blood pressure, diabetes, smoking and hearing loss.
One reason, Barnes says, is sheer prevalence. Obesity has become much more common over the past decade, so it is contributing to more cases of dementia.
Meanwhile, she says, recent studies have suggested the link between low education levels and dementia is stronger than previously thought. So the researchers estimate that factor is contributing to more dementia cases among Americans.
But the relative importance of those factors among different groups of Americans does differ. Along with the differences seen among racial/ethnic groups, men and women showed some variance. Modifiable risk factors played a bigger role in men's dementia risk -- with 36% of cases tied to those factors, versus 30% among women.
Depression was also a bigger contributor for women, compared with men. Among women, almost 11% of dementia cases could be tied to a lifetime history of depression, according to co-researcher Dr. Roch Nianogo, of the University of California, Los Angeles School of Public Health.
Nearly one-quarter of women in the study said they'd been diagnosed with depression at some point.
Edelmayer says that research is now moving beyond finding associations to testing ways to curb dementia risk.
"We think that adopting a combination of healthy behaviors may be most effective," Edelmayer shares.
The Alzheimer's Association is funding a trial called U.S. POINTER, which is testing that combo approach among seniors at increased risk of dementia. The lifestyle measures include exercise, mentally stimulating activities, and better control of high blood pressure and diabetes.
It's critical, Edelmayer says, that studies recruit people of color, who have historically been underrepresented in medical research. As this study shows, the top modifiable risk factors for dementia vary among different groups of Americans.
In the meantime, the Alzheimer's Association recommends doing the following to protect your brain health:
- Break a sweat: Several studies have found an association between physical activity and reduced risk of cognitive decline.
- Hit the books: It's never too late to further your education. It will help reduce your risk of cognitive decline and dementia. This can be as simple as taking a class at a local college, community center or online.
- Butt out: Evidence shows that smoking increases the risk of cognitive decline. However, those that quit smoking can reduce their risk to levels that are comparable to those who have not smoked.
- Heads up!: Brain injury can raise your risk of cognitive decline and dementia. Wearing a seat belt, using a helmet when playing contact sports or riding a bike, and taking steps to prevent falls can help prevent brain injuries.
- Fuel up: Eat a healthy and balanced diet that is lower in fat and higher in vegetables and fruit to help reduce the risk of cognitive decline.
- Catch some zzz's: Not getting enough sleep due to conditions like insomnia or sleep apnea may result in problems with memory and thinking.
- Take care of your mental health: Some studies link a history of depression with an increased risk of cognitive decline. You can combat this by seeking medical treatment if you have symptoms of depression, anxiety or other mental health concerns and managing your stress.
- Buddy up: Staying socially engaged supports brain health. Try pursuing social activities that are meaningful to you or spending time with friends and family.
- Stump yourself: Challenge and activate your mind by doing something that makes you think strategically such as building furniture or doing a puzzle.
