State and detailed county-level estimates show vast disparities in the prevalence of Alzheimer's disease based on racial and socioeconomic factors. Older Americans, women, Black and Hispanic Americans, and those with lower education levels are at higher risk for developing Alzheimer's dementia, according to data from the Chicago Health and Aging Project, on which these estimates were based.

The East and Southeast regions of the U.S. were estimated to have the highest prevalence of Alzheimer's, particularly Maryland, New York, Florida, Mississippi, and Louisiana. In Maryland, nearly 30% of residents are Black, and a slightly higher share of the population is 85 and older compared to national numbers—substantial risk factors that earn it the #1 spot.

In addition to a high prevalence of the disease, Mississippi has the highest Alzheimer's mortality rate, largely due to having the worst-quality health care system in the country, Time reported.

Some of the most afflicted counties are home to Black and Hispanic populations in the South, low-income populations in Appalachia, and older adults in Florida, according to Time. Other studies have found that people in rural areas tend to be underdiagnosed or diagnosed in later stages of dementia, delaying or preventing potential treatments.

Read on to see where in South Dakota has the highest prevalence of Alzheimer's, ranked by the share of the 65 and over population estimated to have the disease. Initial ties were broken by the number of people estimated to have Alzheimer's, but some ties may remain.

- Share of 65+ population with Alzheimer's: 10.0%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 10.0%
- Number of 65+ population with Alzheimer's: 300 people
*These are estimates; actual values have a 95% likelihood of being within 0.5 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 10.1%
- Number of 65+ population with Alzheimer's: Not available
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 10.1%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.5 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 10.2%
- Number of 65+ population with Alzheimer's: Not available
*These are estimates; actual values have a 95% likelihood of being within 0.5 percentage points—or 50 people—of the estimate.

- Share of 65+ population with Alzheimer's: 10.2%
- Number of 65+ population with Alzheimer's: 500 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 50 people—of the estimate.

- Share of 65+ population with Alzheimer's: 10.3%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 10.5%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.5 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 10.5%
- Number of 65+ population with Alzheimer's: 300 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 10.6%
- Number of 65+ population with Alzheimer's: Not available
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 10.7%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 10.8%
- Number of 65+ population with Alzheimer's: Not available
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 10.8%
- Number of 65+ population with Alzheimer's: Not available
*These are estimates; actual values have a 95% likelihood of being within 0.5 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 10.8%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.5 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.0%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.1%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.1%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.1%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.2%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 50 people—of the estimate.

- Share of 65+ population with Alzheimer's: 11.2%
- Number of 65+ population with Alzheimer's: 500 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.2%
- Number of 65+ population with Alzheimer's: 600 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.4%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.5%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.5%
- Number of 65+ population with Alzheimer's: 400 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.6%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.6%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.6%
- Number of 65+ population with Alzheimer's: 800 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 50 people—of the estimate.

- Share of 65+ population with Alzheimer's: 11.7%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.7%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.7%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.7%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.8%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.9%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.9%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.9%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 11.9%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 12.0%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 12.0%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 12.0%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 12.1%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 50 people—of the estimate.

- Share of 65+ population with Alzheimer's: 12.1%
- Number of 65+ population with Alzheimer's: 500 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 12.2%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 12.3%
- Number of 65+ population with Alzheimer's: Not available
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 12.3%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 12.3%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 12.6%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 12.9%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.7 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 13.2%
- Number of 65+ population with Alzheimer's: 200 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 13.5%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

- Share of 65+ population with Alzheimer's: 13.5%
- Number of 65+ population with Alzheimer's: 100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points of the estimate.

This story features data reporting by and writing by Paxtyn Merten and is part of a series utilizing data automation across 50 states.