Your Dementia Risk May Depend on Your ZIP Code

Why are rates highest in the Southeast and lowest in the mid-Atlantic?

Freda Kreier,

AARP

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En español

Published June 13, 2025

A map of the United States with a magnifying glass focusing on the states of Kentucky, Tennessee, Alabama and Mississippi

AARP (Getty Images)

Where you put down roots in the United States might shape your risk of developing dementia — at least that seems to be the case among mostly white and male veterans.

A growing body of evidence suggests that location plays a role in who experiences dementia, which is cognitive decline that’s bad enough to interfere with a person’s daily life. A study published June 9 in JAMA Neurology finds that older veterans in some parts of the United States are up to 25 percent more likely to develop dementia than their peers in other parts of the country.

These results are “striking,” says study author Kristine Yaffe, M.D., a neurologist and epidemiologist at the University of California, San Francisco. “We’re very excited to find out what’s behind this.”

Data on regional rates of dementia could help researchers better understand risk factors for the disease, she says. It can also help policymakers decide where to spend resources for preventing and treating dementia in the future. Yaffe is also chair of AARP’s Global Council on Brain Health.

Regional risk factors

Dementia has many risk factors, including how much education a person has attained, access to health care, social isolation, cardiovascular health and more. How likely someone is to be exposed to these factors can also be influenced by where they live.

Now, research suggests that location itself can help explain who gets dementia. In Europe, some countries have found that their populations have higher rates of dementia than their neighbors. (Italy is highest, at around 2 percent of its total 2018 population, and Ireland is lowest, at 1.09 percent, according to Alzheimer Europe.)

In the U.S., a study reported by Yaffe and her colleagues in 2023 concluded that veterans living in disadvantaged neighborhoods are more likely to develop dementia than veterans living in other locales.

Data on veterans

Studying dementia on a population level is challenging, says Anthony Levinson, M.D., a neuropsychiatrist at McMaster University in Hamilton, Ontario. Dementia can develop slowly over many years, making it hard to track. Also, patients might rarely — or never — sign into health care systems, one way researchers access information on dementia diagnoses.

The Veterans Health Administration (VHA) is “pretty much one of the best data [sources]” for studying population-level differences, Levinson says. It has been collecting data on veterans and dementia across the United States since 1999. Veterans are more likely to have access to health care, making it easy to control for that variable.

In the new study, researchers randomly selected more than 1.2 million veterans age 65 or older who received care at a VHA medical center between 1999 and 2021 and followed them for an average of 13 years. The cohort was 98 percent male and nearly entirely white.

The analysis split the country into 10 regions, based on U.S. Centers for Disease Control and Prevention guidelines. Overall, the Southern and Western United States had higher rates of dementia than the rest of the country, sometimes over 20 percent higher than the mid-Atlantic, the region with the lowest rates. These findings held even when the researchers adjusted for risk factors such as diabetes, cardiovascular health and education. The states in the region with the highest dementia risk were:

Kentucky
Tennessee
Alabama
Mississippi

The areas with lower incidence — meaning fewer veterans developed dementia during their time in the system — were clustered in states across the Northeast and Midwest. States and territories in the region with the lowest dementia rates were:

Delaware
Washington, D.C.
Maryland
Pennsylvania
Virginia
West Virginia
New Jersey

Why the difference in dementia rates?

It’s not clear why veterans living in some U.S. regions are more likely to develop dementia than others. But Yaffe has some theories. Some of the areas with higher rates of dementia were also those with lower educational attainment, meaning residents didn’t stay in school as long as people in other parts of the country.

A 2017 study suggests that staying in school for longer periods might explain a drop in the prevalence of dementia among boomers. Clinicians now think that quality education may help delay dementia in some cases.

Other factors, like diet and exercise, might also play a role. After Alzheimer’s disease, vascular dementia — which is caused by reduced blood flow to the brain — is the second leading cause of dementia in the United States. A 2024 study using Medicare data found that 33 percent of regional differences in U.S. dementia diagnosis rates could be attributed to factors like obesity and smoking, which are risk factors for vascular dementia.

However, the current study, because it was limited almost exclusively to white men, couldn’t account for some dementia risks. Race, ethnicity and sex all play a role in dementia. For instance, researchers have identified genetic variants that may increase people’s risk of dementia that largely affect women and African Americans.

While it’s true that the study looks at a “somewhat select population,” it’s still “an important clue” for working out how regions shape dementia risk in the U.S., Levinson says.

“It’s good for people at an individual level to understand their risk,” he says. On a population level, “maybe it’s time for a little bit more of a nuanced approach that takes into consideration regional variation,” he adds.

This research adds to a growing body of evidence showing that “where you live in the United States may influence your risk of developing dementia,” Levinson says.

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