Study Highlights 3 Risk Factors for Alzheimer’s Disease

Ten years ago, researchers found that about one in three cases of Alzheimer’s disease was associated with modifiable risk factors such as smoking and lack of physical activity.

Now, the same researchers from the University of California have published new data in JAMA Neurology that show these risk factors for Alzheimer’s or another form of dementia depend on a person’s sex, race, and ethnicity.

The study's findings also suggest that people can take steps to reduce their risk of cognitive decline as they age.

Roch A. Nianogo, MD, PhD, MPH, lead author of the study and an assistant professor of epidemiology at the University of California Los Angeles Fielding School of Public Health told Verywell that “engaging in healthy lifestyle behaviors such as maintaining a healthy weight or regularly exercising, which help prevent other chronic diseases such as heart diseases, could also play a critical role in Alzheimer’s disease prevention."

And you don't have to undertake them all at once. Nianogo said that "even if you begin with one or two, you’re moving in the right direction.” 

Modifiable Alzheimer's Risk Factors

The new study revisited risk factors that were associated with Alzheimer’s a decade ago to see whether they had changed over time. Researchers also wanted to investigate if modifiable risk factors differed across race, ethnicity, and gender.

The researchers found that about a third of Alzheimer’s cases were related to a combination of eight modifiable lifestyle risk factors, including:

• Midlife obesity
• Physical inactivity
• Low educational attainment
• Depression
• Diabetes
• Hearing loss
• Midlife high blood pressure
• Smoking 

One interesting finding was related to physical activity levels. In 2011, a large number of Alzheimer's cases involved a lack of physical activity, depression, and smoking. However, in the current study, most Alzheimer’s cases were associated with midlife obesity (17.7%), physical inactivity (11.8%), and low educational attainment (11.7%).

“There exist modifiable risk factors such as midlife obesity and physical inactivity that could contribute to a non-negligible proportion of Alzheimer’s disease cases today and the relative contribution of several risk factors to Alzheimer’s disease cases has changed over the past decade,” said Nianogo.

Alzheimer’s Risk Factors by Race and Ethnicity

Among all racial and ethnic groups, the Asian participants were the least likely to smoke, have midlife obesity, or have midlife hypertension. Meanwhile, American Indian and Alaska Native participants had the highest rates among all three risk factors.

Black and Hispanic participants had high rates of midlife obesity. Hispanic participants were the most likely to report a low education, followed by American Indian and Alaska Native participants.

Considering all the modifiable risk factors, the researchers found Black participants had the highest Alzheimer’s cases among ethnic and racial groups.

“Older African Americans are about twice as likely to have Alzheimer’s or other dementias as older Whites. Hispanic Americans are about one and one-half times as likely,” Percy Griffin, PhD, the director of scientific engagement at the Alzheimer’s Association, told Verywell. Griffin was not involved with the study.

Midlife obesity contributed the most to Alzheimer’s risk among a racial or ethnic group. Compared to other groups, Black participants were more likely to be impacted by midlife obesity.

Alzheimer’s Risk Factors by Sex 

The researchers also noticed Alzheimer’s risk factors for men and women were not the same.

Women were more likely than men to report depression, but men reported more cases of midlife high blood pressure. Midlife obesity was the biggest contributor to Alzheimer’s risk in men, while depression was more prominent in women.

Nianogo said that a surprising finding was that most of the Alzheimer’s cases in the study population occurred in men.

“This could be seen as being at odds with the fact that almost two-thirds of Americans with Alzheimer’s are women," said Nianogo. "Meaning that out of all Alzheimer’s cases, there is a higher proportion of women compared to men."

According to Nianogo, one reason for the finding could be that, except for depression and physical inactivity, men had a higher prevalence of the other modifiable risk factors for Alzheimer's such as smoking and midlife hypertension.

Who Was Included?

The team collected 2018 data from the Centers for Disease Control and Prevention (CDC)’s Behavioral Risk Factor Surveillance System (BRFSS)—an annual national survey of noninstitutionalized adults living in the U.S.

The survey involved questions regarding Americans’ lifestyle choices, health conditions, and use of medical services. The survey excluded people in psychiatric centers, prisons, or hospitals.

However, Nianogo said that the data used in the study still captured relevant information for estimating groups of older aged people or people with certain mental illnesses such as depression.

Survey data from about 378,615 individuals were included in the study. The researchers looked at whether the people in the study had Alzheimer’s, another form of dementia, or known risk factors for Alzheimer’s.

Of the 378,615 individuals, 48.7% were male and 21.1% were 65 or older. Of those, nearly 65% were White, 11.7% were Black, 16% were Hispanic, and 0.9% were American Indian or Alaska Native.

Is Prevention Possible?

People are not necessarily powerless when it comes to prevention. Griffin said there is also evidence that combining multiple healthy habits that target modifiable risk factors could prevent or delay up to 40% of dementia cases.

Alzheimer’s disease has no cure. While age and genetics are two Alzheimer risk factors you can't control, there are ways you can reduce your overall risk for cognitive decline and Alzheimer’s, such as:

• Eating a heart-healthy diet
• Exercising regularly
• Staying cognitively sharp and socially engaged
• Do not use tobacco products or quit if you do
• Avoiding drinking excess alcohol