The Big Risk Factors for Dementia to Avoid

High blood sugar, hearing loss and low educational levels named top three risk factors for dementia in U.S. population

Liz Szabo,

AARP

Comments

En español

Published November 13, 2025

An illustration of a brain surrounded by images symbolizing dementia risk factors

AARP (Getty Images,3)

A growing body of research shows that almost half the cases of dementia are potentially preventable or delayable through lifestyle changes or public policies that promote brain health.

High blood sugar, hearing loss and low educational attainment are the strongest and most consistent risk factors for dementia in the United States, according to an analysis of more than 600 studies.

The analysis looked at 12 risk factors established in 2020 by the Lancet Commission on Dementia Prevention, Intervention and Care. (The commission’s 2024 report, which added high cholesterol and vision loss, was not out when this research began.) This two-year project focused on the U.S. population and pointed out differences by state.

“Understanding which factors have the greatest impact on dementia puts us in a stronger position to reduce the risk in our communities,” says Juan Rodriguez, AARP’s vice president, brain health. “These findings offer clear steps people and communities can take today to support their brain health, promote healthy aging and give older Americans more quality time to live their lives as they choose.”

The research was a collaboration between AARP, the Alzheimer’s Disease Data Initiative (AD Data Initiative) and the Institute for Health Metrics and Evaluation at the University of Washington (IHME). The findings, including state-by-state comparisons, are available for non-commercial research via the AD Workbench.

High blood sugar

These risk factors for dementia are modifiable by personal actions or policy changes:

High blood sugar
Hearing loss
Low education level
Air pollution
Depression
Physical inactivity
Traumatic brain injury
Smoking
High blood pressure
Social isolation

Researchers found the strongest evidence of a link to dementia for high blood sugar, which damages tiny blood vessels in the brain. The risk of dementia increased both among people with diabetes and prediabetes.

The risk of dementia for someone with a fasting blood sugar of 6.1 mmol/liter (or 110 mg/dL) — which meets the World Health Organization’s definition of prediabetes — is 15 to 32 percent higher than for someone with a fasting blood sugar in the normal range, which is 4.8 to 5.4 mmol/liter, according to the analysis. People with a fasting blood sugar of 7.0 mmol/liter (or 126 mg/dL) — which meets the WHO’s definition of diabetes — had a 35 to 55 percent higher risk.

More than 40 million people — or 12 percent of the U.S. population — had diabetes in 2023, according to the Global Burden of Diseases, Injuries, and Risk Factors Study, reported in The Lancet in 2025.

More than 7 million Americans have Alzheimer’s disease, the most common form of dementia, according to the Alzheimer’s Association. By 2050, that figure is projected to rise to nearly 13 million.

Hearing loss

People with moderate hearing loss are 29 percent more likely to develop dementia than people with normal hearing; those with severe hearing loss are 49 percent more likely, according to the analysis.

Wearing hearing aids can reduce that risk. A study in The Lancet found that older people at risk of dementia who wore hearing aids experienced 48 percent less cognitive decline over three years than peers who did not, as measured by annual assessments.

Low educational levels

The less education a person has, the more likely they are to develop dementia. Compared with people who receive 18 years of education — equivalent to graduating from high school, college and graduate school — people who go to school for 12 years were 23 percent more likely to develop dementia.

While learning stimulates the brain, greater educational achievement is also associated with a higher income. Having more money increases a person’s odds of having access to medical care, a nutritious diet, a safe neighborhood with clean air and stable housing, all of which contribute to better health, says Dr. Ariel Green, a geriatrician and associate professor of medicine at the Johns Hopkins University School of Medicine.

While people cannot change the quality or quantity of education they received in their youth, the study can help guide public policy, says Jaimie Steinmetz, lead research scientist at IHME. The analysis suggests that investing in schools now could lower the burden of dementia in decades to come.

Researchers did not study the effect of brain games, crossword puzzles or other strategies that people may use to engage their brains in older adulthood, Steinmetz says. Other research suggests, however, that stimulating the brain by learning new things in adulthood helps the brain make new connections.

Additional important risk factors

The analysis listed seven other major contributors to dementia risk. They are: air pollution, depression, physical inactivity, traumatic brain injury resulting in hospitalization, smoking, high blood pressure, and social isolation. Alcohol use and high body mass index had the most inconsistent relationship with dementia risk in the studies reviewed.

This report has some overlap with a 2024 study of U.K. residents, which named diabetes, alcohol consumption (measured by frequency) and exposure to air pollution as the most harmful modifiable risk factors for dementia out of 15 that were studied and published in the journal Nature Communications. A team of researchers examined brain scans of nearly 40,000 UK Biobank participants and found that parts of the brain associated with Alzheimer’s disease, which are more prone to earlier and accelerated aging, were most affected by these three factors.

State differences stand out when it comes to air pollution

High blood glucose was the number one risk factor in all states except California, where air pollution took the number one spot. Americans’ exposure to air pollution has dropped dramatically since the passage of the Clean Air Act of 1970. Back then, pollution from factories in the East and Midwest plus automobile exhaust were major drivers of air pollution.

Today, a significant amount of pollution comes from wildfires in western states, says Dr. Mitchell S. V. Elkind, chief science officer for brain health and stroke at the American Heart Association. California ranks as the worst state in the country for air pollution, according to the analysis, while Hawaii has the cleanest air. Outdoor air pollution accounted for 1.5 percent of the burden of dementia-related health loss in Hawaii in 2023, compared with 20 percent of the burden in California, the analysis shows.

Communities with long-term exposure to air pollution are 14 percent more likely to develop dementia compared with people living in areas with very clean air.

Not everyone has the resources to move to a state with cleaner air. Steinmetz says the analysis can help policymakers better understand how much pollution contributes to dementia in their states. Slicing and dicing the data by state should help state officials decide where to focus. “Ranking risk factors by state allows policymakers to understand where to allocate resources most efficiently,” says Niranjan Bose, interim executive director of the AD Data Initiative. More details about the drivers of dementia risk can be viewed using the IHME Brain Health Atlas.