US States, Counties With Highest Alzheimer's Prevalence Rates Identified

Pauline Anderson

July 17, 2023

Eastern and southeastern areas of the US have the highest rates of Alzheimer's disease (AD), new research shows.

Investigators at Rush University in Chicago, Illinois, found AD prevalence was highest in Maryland, New York, Mississippi, and Florida. At the county level, Miami-Dade in Florida, Baltimore in Maryland, and the Bronx in New York were among the US counties with the highest prevalence of the disease.

Such geographical variations may be due to the unique make-up of regional populations, study investigator Kumar Rajan, PhD, professor of Medicine and director of Rush Institute for Healthy Aging, Rush University Medical Center, in Chicago, told Medscape Medical News.

Rajan presented the research at the Alzheimer's Association International Conference (AAIC) 2023.

High-Impact Research

An estimated 6.7 million Americans are living with AD, a figure that’s expected to double by 2050. Estimating the prevalence of Alzheimer's across states' counties can provide a better understanding of region-specific disease burden and have policy implications for resource allocation, Rajan noted.

To determine the state- and county-specific prevalence of AD, the researchers applied AD data from the Chicago Health and Aging Project (CHAP), a population-based study that's about 60% African American, to county- and state-level data from the National Center for Health Statistics (NCHS).

"We used estimates in our study in Chicago, which began in the 1990s and has approximately 10,800 people, and projected those estimates to county-level populations to see what the variations look like," said Rajan.

Of 3142 counties in 50 states, the east and southeastern regions of the US had the highest AD prevalence. For states, the highest rates were in Maryland (12.9%), New York (12.7%), Mississippi (12.5%), and Florida (12.5%).

California and Illinois were also among the top 10 states with the highest prevalence of Alzheimer’s.

California had the highest number of residents, with 719,000 (95% CI, 665.0 to 774.4 thousand), followed by Florida with 579,000 (95% CI, 539.9 to 620.0 thousand), and Texas with 459,000 (95% CI, 422.7 to 496.0 thousand).

The three counties with the highest prevalence, all with 16.6%, were Miami-Dade County in Florida, Baltimore city in Maryland, and Bronx County in New York.

One county in the top 10 for AD prevalence was El Paso, Texas, which Rajan found "a bit surprising," as Texas was not among the top four states with the highest prevalence.

In addition to older age, what’s likely driving elevated AD prevalence in these areas is the substantially larger proportion of minority populations who are at higher risk for AD, possibly due to health disparities, said Rajan.

Determining local-level estimates of AD should have "a very high impact" on public health programs aimed at AD prevention, detection, and treatment, he said. In addition, as more AD drugs are approved, there will likely be county-level and even state-level implications for Medicare coverage, he added.

In addition, these new findings could help physicians treating or caring for minority populations "understand the landscape of what the disease looks like," said Rajan.

A limitation of the study was that it was based on data from a single study, he noted.

The next step is to expand this research. Rajan and others are establishing the Regional and Ethnic Variations in Alzheimer’s and Cognitive Health Consortium, with the goal of gaining a better understanding of AD prevalence across six US regions.

Optimal Resource Distribution

Commenting on the study for Medscape Medical News, Percy Griffin, PhD, director, Scientific Engagement, Alzheimer’s Association, said the research provides useful information about AD prevalence at the local level.

"We need to understand how specific demographics and characteristics can help explain some of the high prevalence in certain areas."

Compared with White Americans, Griffin noted that Black Americans are twice as likely to have AD, and older Hispanic Americans are 1.5 times as likely.

This new data will help pinpoint areas of high risk and high need so that funding, staffing, and other resources for those with AD and other dementias can be optimally distributed, he said.

"It gives us that kind of geographic specificity in terms of the prevalence so we can dig deeper and better allocate resources on a county level," he added.

The Alzheimer’s Association "is fully committed to working with local agencies and being in the communities to assist them in their efforts to intervene in this disease."

The study also highlights the need for more research to determine what factors other than age and race — such as potential environmental factors — might affect regional AD prevalence, he said.

The study received funding from the National Institutes of Health.

Rajan and Griffin report no relevant financial relationships.

AAIC 2023 Abstract #74430. Presented July 17, 2023.

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