Dementia affects more than 6 million Americans and accounts for more than 100,000 deaths each year, according to the National Institutes of Health. Further, researchers estimate that 42% of Americans over 55 will eventually develop dementia—and that an aging U.S. population could cause the number of new dementia cases per year to double by 2060.

Now, researchers at the University of California San Francisco have identified the U.S. regions, as defined by the Centers for Disease Control and Prevention, where dementia occurs most often.

The large and comprehensive study, published in JAMA Neurology, examined data on more than 12.6 million veterans 65 and older enrolled in the Veterans Health Administration system; only 2% were women.

Researchers found the highest incidence in the Southeast (North Carolina, South Carolina, Georgia, Florida) and the lowest in the Mid-Atlantic states (Delaware, Maryland, Pennsylvania, Virginia, West Virginia, New Jersey, Washington D.C.).

Further, using the low Mid-Atlantic region for comparison, dementia incidence was:

25% higher in the Southeast (Kentucky, Tennessee, Alabama, and Mississippi)
23% higher in the Northwest (Alaska, Idaho, Oregon, and Washington)
23% higher Rocky Mountains (Colorado, Montana, North Dakota, South Dakota, Utah, and Wyoming)
18% higher in the South (Arkansas, Louisiana, New Mexico, Oklahoma, and Texas)
13% in the Southwest (Arizona, California, Hawaiʻi, and Nevada)
12% higher in the South Atlantic (North Carolina, South Carolina, Georgia, and Florida)
12% higher in the Midwest (Iowa, Kansas, Missouri, and Nebraska)
7% higher in the Northeast (Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont, and New York)
7% higher in the Great Lakes (Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin)

What accounts for the differences in dementia incidence?

Regional variation may be influenced by several factors, the study notes, pointing to prior research which suggests demographic factors including sex, race, ethnicity, and education level impact the risk of dementia across populations.

The prevalence and management of cardiovascular disease and related risk factors, known to increase risk of dementia and cognitive decline, vary across the country.^“Rurality of residence may also play a role,” wrote the researchers, “with studies showing greater dementia and cognitive impairment among rural adults, possibly due to health care access or poverty.”

The results, they add, “underscore the influence of regionally patterned risk factors or diagnostic practices, highlighting the importance of tailored health care strategies, public health initiatives, and policy reforms.”

The varied findings highlight the need for targeted health care planning, public health interventions, and policy development—as well as more research. “Quality of education, early life conditions, and environmental exposures may be among those factors,” lead author Christina Dintica, PhD, said in a news release. But the next important step, she said, is to investigate the factors driving these differences.

These states have the highest rates of dementia in the U.S., new study finds