An estimated 719,700 people in California over age 65 have Alzheimer's, according to estimates released by the Alzheimer's Association in 2023.
Alzheimer's disease afflicts an estimated 6.7 million Americans, and that number is only growing. Medical professionals believe the volume of diagnoses could double by 2060 if there isn't a breakthrough in prevention—or a cure.
For the first time, the Alzheimer's Association released estimates on Alzheimer's prevalence in each state and county. Researchers hope these figures will help regional public health officials better treat Alzheimer's patients, develop localized care plans, and budget for care—particularly as new treatments come at a cost.
Alzheimer's is the most common form of dementia and is among the top 10 causes of death in the U.S. These deaths are increasing as fatality rates from other health-related causes, including heart disease and stroke, are on the decline. With Alzheimer's, the brain shrinks, brain cells die, and peoples' memory and language centers fail. As the disease advances, the loss of brain function leads to dehydration, malnutrition, infection, and ultimately death.
Developing a cure or effective treatment has been slow, as medical professionals still don't know what causes Alzheimer's. But earlier this year, the Food and Drug Administration fully greenlit the first drug proven to effectively treat the disease: lecanemab (sold under the brand name Leqembi), created by Eisai Inc. and Biogen. Earlier treatments only addressed symptoms of Alzheimer's, while lecanemab treats the early stages of the disease itself and slows its progression.
The drug costs $26,500 annually and is partially covered by Medicare if a patient's medical team participates in a registry to track the drug's outcomes. Those high costs could keep the treatment out of reach for low-income Americans, who already have higher odds of developing Alzheimer's, studies have shown.
Nearly all Alzheimer's patients are on government insurance, and estimates show that Medicare could spend $2 billion to $5 billion annually on lecanemab and related care. That pales in comparison to the $345 billion that Alzheimer's and other dementias cost in 2023, including nursing home stays, symptom management medications, and other care for those with the disease. Without medical advancements, the Alzheimer's Association expects those costs could rise to nearly $1 trillion by 2050.
If lecanemab and similar drugs can slow progression in even half of mild Alzheimer's patients, one study from the University of Chicago estimates Americans would save $212 billion to over $1 trillion in care-related costs over the next decade.
Having a treatment to slow the progression of Alzheimer's also creates more urgency to diagnose the disease sooner to retain more brain function. Warning signs for the disease include disruptive memory loss, difficulty with familiar tasks, worsening judgment, and changes in mood and personality.
The U.S. has a shortage of specialists in elder and memory-related medicine and nurses providing care at nursing homes and assisted-living facilities. In regions with high rates of Alzheimer's, these shortages could be catastrophic within the current models of care.
Stacker mapped states by the share of the population over age 65 that is estimated to have Alzheimer's disease, using data released by the Alzheimer's Association in July 2023. As a part of the national analysis, Stacker also took a closer look at California and ranked the counties within it by their estimated Alzheimer's prevalence.
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Alzheimer's rates by state
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 California 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.
#58. Alpine County
- Share of 65+ population with Alzheimer's: 8.1%
- 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.
#57. Mono County
- Share of 65+ population with Alzheimer's: 9.3%
- 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.
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4 / 59#56. Trinity County
- Share of 65+ population with Alzheimer's: 9.3%
- 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—or 50 people—of the estimate.
#55. Plumas County
- Share of 65+ population with Alzheimer's: 9.4%
- 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.
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#54. Humboldt County
- Share of 65+ population with Alzheimer's: 9.7%
- Number of 65+ population with Alzheimer's: 2,500 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 150 people—of the estimate.
#53. Sierra County
- Share of 65+ population with Alzheimer's: 9.8%
- 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.
#52. Siskiyou County
- Share of 65+ population with Alzheimer's: 9.8%
- Number of 65+ population with Alzheimer's: 1,100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 50 people—of the estimate.
#51. Del Norte County
- Share of 65+ population with Alzheimer's: 9.9%
- 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.
#50. Mendocino County
- Share of 65+ population with Alzheimer's: 9.9%
- Number of 65+ population with Alzheimer's: 2,000 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 150 people—of the estimate.
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#49. Nevada County
- Share of 65+ population with Alzheimer's: 9.9%
- Number of 65+ population with Alzheimer's: 2,800 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 150 people—of the estimate.
#48. Amador County
- Share of 65+ population with Alzheimer's: 10.0%
- Number of 65+ population with Alzheimer's: 1,100 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 50 people—of the estimate.
#47. Calaveras County
- Share of 65+ population with Alzheimer's: 10.0%
- Number of 65+ population with Alzheimer's: 1,300 people
*These are estimates; actual values have a 95% likelihood of being within 0.7 percentage points—or 50 people—of the estimate.
#46. El Dorado County
- Share of 65+ population with Alzheimer's: 10.0%
- Number of 65+ population with Alzheimer's: 4,400 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 300 people—of the estimate.
#45. Lassen County
- Share of 65+ population with Alzheimer's: 10.1%
- 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.
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#44. Yuba County
- Share of 65+ population with Alzheimer's: 10.2%
- Number of 65+ population with Alzheimer's: 1,100 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 100 people—of the estimate.
#42. Lake County (tie)
- Share of 65+ population with Alzheimer's: 10.2%
- Number of 65+ population with Alzheimer's: 1,500 people
*These are estimates; actual values have a 95% likelihood of being within 0.7 percentage points—or 100 people—of the estimate.
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18 / 59#42. Tuolumne County (tie)
- Share of 65+ population with Alzheimer's: 10.2%
- Number of 65+ population with Alzheimer's: 1,500 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 100 people—of the estimate.
#41. Shasta County
- Share of 65+ population with Alzheimer's: 10.2%
- Number of 65+ population with Alzheimer's: 3,900 people
*These are estimates; actual values have a 95% likelihood of being within 0.6 percentage points—or 200 people—of the estimate.
#40. Santa Cruz County
- Share of 65+ population with Alzheimer's: 10.3%
- Number of 65+ population with Alzheimer's: 5,000 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 400 people—of the estimate.
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#39. Modoc County
- Share of 65+ population with Alzheimer's: 10.4%
- 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—or 50 people—of the estimate.
#38. Mariposa County
- Share of 65+ population with Alzheimer's: 10.4%
- 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.
#37. Sonoma County
- Share of 65+ population with Alzheimer's: 10.5%
- Number of 65+ population with Alzheimer's: 10,900 people
*These are estimates; actual values have a 95% likelihood of being within 0.7 percentage points—or 650 people—of the estimate.
#36. San Luis Obispo County
- Share of 65+ population with Alzheimer's: 10.6%
- Number of 65+ population with Alzheimer's: 6,400 people
*These are estimates; actual values have a 95% likelihood of being within 0.7 percentage points—or 400 people—of the estimate.
#35. Butte County
- Share of 65+ population with Alzheimer's: 10.7%
- Number of 65+ population with Alzheimer's: 4,200 people
*These are estimates; actual values have a 95% likelihood of being within 0.7 percentage points—or 250 people—of the estimate.
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#34. Tehama County
- Share of 65+ population with Alzheimer's: 10.8%
- Number of 65+ population with Alzheimer's: 1,400 people
*These are estimates; actual values have a 95% likelihood of being within 0.7 percentage points—or 100 people—of the estimate.
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27 / 59#33. Glenn County
- Share of 65+ population with Alzheimer's: 11.0%
- Number of 65+ population with Alzheimer's: 500 people
*These are estimates; actual values have a 95% likelihood of being within 0.9 percentage points—or 50 people—of the estimate.
#32. Marin County
- Share of 65+ population with Alzheimer's: 11.1%
- Number of 65+ population with Alzheimer's: 6,700 people
*These are estimates; actual values have a 95% likelihood of being within 0.7 percentage points—or 400 people—of the estimate.
#31. Placer County
- Share of 65+ population with Alzheimer's: 11.1%
- Number of 65+ population with Alzheimer's: 9,100 people
*These are estimates; actual values have a 95% likelihood of being within 0.7 percentage points—or 550 people—of the estimate.
#30. Inyo County
- 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 0.7 percentage points of the estimate.
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#29. Madera County
- Share of 65+ population with Alzheimer's: 11.4%
- Number of 65+ population with Alzheimer's: 2,600 people
*These are estimates; actual values have a 95% likelihood of being within 1.1 percentage points—or 250 people—of the estimate.
#28. Kern County
- Share of 65+ population with Alzheimer's: 11.4%
- Number of 65+ population with Alzheimer's: 11,900 people
*These are estimates; actual values have a 95% likelihood of being within 1.0 percentage points—or 1,100 people—of the estimate.
#27. Napa County
- Share of 65+ population with Alzheimer's: 11.5%
- Number of 65+ population with Alzheimer's: 3,200 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 200 people—of the estimate.
#26. Yolo County
- Share of 65+ population with Alzheimer's: 11.5%
- Number of 65+ population with Alzheimer's: 3,400 people
*These are estimates; actual values have a 95% likelihood of being within 0.9 percentage points—or 250 people—of the estimate.
#25. Sacramento County
- Share of 65+ population with Alzheimer's: 11.5%
- Number of 65+ population with Alzheimer's: 26,600 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 1,700 people—of the estimate.
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#24. Stanislaus County
- Share of 65+ population with Alzheimer's: 11.6%
- Number of 65+ population with Alzheimer's: 8,700 people
*These are estimates; actual values have a 95% likelihood of being within 1.0 percentage points—or 700 people—of the estimate.
#23. Orange County
- Share of 65+ population with Alzheimer's: 11.6%
- Number of 65+ population with Alzheimer's: 57,800 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 4,100 people—of the estimate.
Matt Gush // Shutterstock
38 / 59#22. Sutter County
- Share of 65+ population with Alzheimer's: 11.7%
- Number of 65+ population with Alzheimer's: 1,800 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 100 people—of the estimate.
#21. Solano County
- Share of 65+ population with Alzheimer's: 11.7%
- Number of 65+ population with Alzheimer's: 8,800 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 600 people—of the estimate.
#20. Contra Costa County
- Share of 65+ population with Alzheimer's: 11.7%
- Number of 65+ population with Alzheimer's: 22,600 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 1,450 people—of the estimate.
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#19. Colusa County
- Share of 65+ population with Alzheimer's: 11.8%
- Number of 65+ population with Alzheimer's: 400 people
*These are estimates; actual values have a 95% likelihood of being within 1.1 percentage points of the estimate.
#18. Ventura County
- Share of 65+ population with Alzheimer's: 11.8%
- Number of 65+ population with Alzheimer's: 16,500 people
*These are estimates; actual values have a 95% likelihood of being within 0.9 percentage points—or 1,300 people—of the estimate.
#17. San Diego County
- Share of 65+ population with Alzheimer's: 11.8%
- Number of 65+ population with Alzheimer's: 58,400 people
*These are estimates; actual values have a 95% likelihood of being within 0.9 percentage points—or 4,300 people—of the estimate.
#16. San Joaquin County
- Share of 65+ population with Alzheimer's: 11.9%
- Number of 65+ population with Alzheimer's: 12,200 people
*These are estimates; actual values have a 95% likelihood of being within 1.0 percentage points—or 950 people—of the estimate.
Uladzik Kryhin // Shutterstock
45 / 59#15. Santa Clara County
- Share of 65+ population with Alzheimer's: 11.9%
- Number of 65+ population with Alzheimer's: 32,300 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 2,150 people—of the estimate.
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#14. San Benito County
- Share of 65+ population with Alzheimer's: 12.0%
- Number of 65+ population with Alzheimer's: 1,000 people
*These are estimates; actual values have a 95% likelihood of being within 1.2 percentage points—or 100 people—of the estimate.
#13. San Mateo County
- Share of 65+ population with Alzheimer's: 12.0%
- Number of 65+ population with Alzheimer's: 15,500 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 1,050 people—of the estimate.
#12. San Bernardino County
- Share of 65+ population with Alzheimer's: 12.0%
- Number of 65+ population with Alzheimer's: 32,200 people
*These are estimates; actual values have a 95% likelihood of being within 1.1 percentage points—or 2,950 people—of the estimate.
#11. Tulare County
- Share of 65+ population with Alzheimer's: 12.1%
- Number of 65+ population with Alzheimer's: 6,700 people
*These are estimates; actual values have a 95% likelihood of being within 1.2 percentage points—or 650 people—of the estimate.
#10. Monterey County
- Share of 65+ population with Alzheimer's: 12.1%
- Number of 65+ population with Alzheimer's: 7,600 people
*These are estimates; actual values have a 95% likelihood of being within 1.0 percentage points—or 600 people—of the estimate.
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#9. Alameda County
- Share of 65+ population with Alzheimer's: 12.1%
- Number of 65+ population with Alzheimer's: 29,700 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 1,850 people—of the estimate.
#8. Fresno County
- Share of 65+ population with Alzheimer's: 12.2%
- Number of 65+ population with Alzheimer's: 15,700 people
*These are estimates; actual values have a 95% likelihood of being within 1.1 percentage points—or 1,400 people—of the estimate.
#7. Riverside County
- Share of 65+ population with Alzheimer's: 12.2%
- Number of 65+ population with Alzheimer's: 46,000 people
*These are estimates; actual values have a 95% likelihood of being within 1.0 percentage points—or 3,650 people—of the estimate.
#6. Merced County
- Share of 65+ population with Alzheimer's: 12.3%
- Number of 65+ population with Alzheimer's: 4,000 people
*These are estimates; actual values have a 95% likelihood of being within 1.2 percentage points—or 350 people—of the estimate.
#5. Santa Barbara County
- Share of 65+ population with Alzheimer's: 12.3%
- Number of 65+ population with Alzheimer's: 8,800 people
*These are estimates; actual values have a 95% likelihood of being within 1.0 percentage points—or 700 people—of the estimate.
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#4. San Francisco County
- Share of 65+ population with Alzheimer's: 12.4%
- Number of 65+ population with Alzheimer's: 17,900 people
*These are estimates; actual values have a 95% likelihood of being within 0.8 percentage points—or 1,100 people—of the estimate.
#3. Kings County
- Share of 65+ population with Alzheimer's: 12.5%
- Number of 65+ population with Alzheimer's: 2,100 people
*These are estimates; actual values have a 95% likelihood of being within 1.2 percentage points—or 200 people—of the estimate.
#2. Los Angeles County
- Share of 65+ population with Alzheimer's: 13.2%
- Number of 65+ population with Alzheimer's: 190,300 people
*These are estimates; actual values have a 95% likelihood of being within 1.1 percentage points—or 16,050 people—of the estimate.
#1. Imperial County
- Share of 65+ population with Alzheimer's: 15.0%
- Number of 65+ population with Alzheimer's: 3,700 people
*These are estimates; actual values have a 95% likelihood of being within 2.0 percentage points—or 500 people—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.
