Investigators at Rush University in Chicago found AD prevalence was highest in Maryland, New York, Mississippi, and Florida. At the county level, Miami-Dade in Florida, Baltimore city, and Bronx County in New York were among the U.S. counties with the highest prevalence of the disease.
Such geographical variations may be caused by 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, Chicago, said in an interview.
Dr. Rajan presented the research at the Alzheimer’s Association International Conference.
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, Dr. Rajan noted.
To determine the state- and county-specific prevalence of AD, the researchers applied AD data from the Chicago Health and Aging Project, a population-based study that’s about 60% African American, to county- and state-level data from the National Center for Health Statistics.
“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 Dr. Rajan.
Of 3,142 counties in 50 states, the East and Southeastern regions of the United States 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% confidence interval, 665,000-774,400), followed by Florida with 579,000 (95% CI, 539,900 to 620,000), and Texas with 459,000 (95% CI, 422,700 to 496,000).
The three counties with the highest prevalence, all with 16.6%, were Miami-Dade County, Baltimore city, and Bronx County.
One county in the top 10 for AD prevalence was El Paso, Tex., which Dr. 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 Dr. 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.
In addition, these new findings could help physicians treating or caring for minority populations “understand the landscape of what the disease looks like,” said Dr. 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. Dr. 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 U.S. regions.