Where you live does not determine whether you will develop Alzheimer’s disease. Still, geography can reveal something important about who is carrying the heaviest burden of the disease, where families may need more support, and which communities could face the greatest pressure on health care and caregiving systems.

A landmark analysis produced the first estimates of Alzheimer’s dementia prevalence for all 3,142 U.S. counties. The headline finding was striking: many of the counties with the highest estimated prevalence among adults age 65 and older were concentrated in the East and Southeast. Miami-Dade County in Florida, Baltimore City in Maryland, and Bronx County in New York shared the top estimated prevalence rate at 16.6%.

That does not mean Alzheimer’s is somehow hiding in the local water supply or checking county lines before moving in. The explanation is far more complicated. Age distribution, racial and ethnic disparities, cardiovascular health, chronic disease, access to care, social conditions, and patterns of diagnosis can all shape the burden a community experiences.

There is also an important date attached to the numbers. The county estimates describe modeled 2020 prevalence. They were first presented publicly in 2023 and continue to appear in major Alzheimer’s reports because they remain the first comprehensive county-by-county estimates of their kind. In other words, the map is highly useful, but it is not a real-time scoreboard.

Which U.S. Counties Had the Highest Estimated Alzheimer’s Prevalence?

Among counties with at least 10,000 residents age 65 or older, researchers identified the following 10 areas as having the highest estimated prevalence of clinical Alzheimer’s dementia:

Eight of these 10 locations are in the eastern or southeastern United States. Imperial County and El Paso County are the geographic exceptions, illustrating an important point: the Alzheimer’s burden cannot be explained by a simple North-versus-South map.

How Researchers Estimated Alzheimer’s Rates by County

Researchers used cognitive data from the Chicago Health and Aging Project, a long-running population study, together with population information to estimate the prevalence of Alzheimer’s dementia among adults age 65 and older. The estimates were then applied across state and county populations using demographic characteristics including age, sex, race, and ethnicity.

This approach made something possible that had not previously been available on a nationwide scale: a comparable estimate for every U.S. county.

Estimated prevalence is not the same as counting medical records

This distinction matters. The numbers do not represent a giant stack of confirmed patient charts collected from every doctor’s office in the country. They are population-based estimates.

That can actually be useful because Alzheimer’s and other dementias are frequently underdiagnosed. Some people live with cognitive impairment for years without receiving a formal diagnosis. Others may have a diagnosis in a medical record but never fully understand what they were told. Relying only on billing codes and documented diagnoses can therefore miss part of the picture.

At the same time, modeled estimates have limitations. They cannot capture every neighborhood-level difference, individual health behavior, environmental exposure, or change that has occurred since 2020. Think of the map as a powerful planning tool, not a crystal ball with county borders drawn on it.

Why Do Some Counties Have Higher Alzheimer’s Prevalence?

There is no single answer. Alzheimer’s disease is complex, and county-level patterns reflect overlapping demographic, medical, economic, and social factors.

Age is the biggest risk factor

Alzheimer’s is not a normal part of aging, but advancing age is its strongest known risk factor. A county with a larger share of people in their late 70s, 80s, and 90s may therefore have a higher prevalence than a younger county.

The age effect becomes especially dramatic among the oldest adults. The Alzheimer’s Association estimated that 7.4 million Americans age 65 and older were living with clinical Alzheimer’s dementia in 2026. About three-quarters were age 75 or older, and prevalence rises sharply among people age 85 and above.

America is also getting older. The 2020 Census counted 55.8 million people age 65 or older, representing about one in six U.S. residents. As the older population grows, even communities where individual risk does not increase may see more families affected simply because there are more older adults.

Racial and ethnic health disparities are part of the pattern

Several high-prevalence counties have large Black or Hispanic populations. Researchers have consistently observed higher dementia prevalence in some Black and Hispanic populations compared with non-Hispanic White populations.

Those differences should not be reduced to race as though it were a simple biological switch. Race and ethnicity often overlap with decades of unequal access to medical care, education, safe neighborhoods, healthy food, economic opportunity, preventive treatment, and protection from chronic stress. Researchers are increasingly examining how these social determinants of health accumulate across a lifetime.

There is another complication: diagnosis itself is not equally distributed. Studies have found racial disparities in when and how dementia is recognized. Some patients may reach specialists later, after symptoms have become more severe. Language barriers, medical mistrust, limited access to memory clinics, transportation problems, and cultural beliefs about aging can all influence when families seek help.

Heart and brain health often travel together

The Southeast has a substantial burden of hypertension, stroke, diabetes, and other cardiovascular or metabolic conditions associated with increased dementia risk. The county prevalence study did not directly incorporate all of these health conditions into its estimates, so it would be wrong to say that high blood pressure alone “caused” a county to rank highly.

Still, the broader connection matters. The brain depends on a healthy blood supply, and conditions that damage blood vessels can contribute to cognitive decline. Alzheimer’s pathology and vascular disease can also occur together, creating a particularly unwelcome medical team-up.

For individuals and communities, that means brain health policy cannot live in a separate little box labeled “memory.” Programs that improve blood pressure control, diabetes care, physical activity, smoking prevention, stroke treatment, and access to primary care may also support healthier cognitive aging.

What the County Rankings Do Not Mean

A top-10 ranking can attract attention, but it can also invite misleading conclusions. Several cautions are essential.

A high county rate does not predict an individual diagnosis

Living in Miami-Dade County, the Bronx, Baltimore, or any other high-prevalence area does not mean a particular resident will develop Alzheimer’s. Individual risk depends on a complex mix of age, genetics, health conditions, lifestyle, environmental exposures, and other factors.

A lower rate does not mean a county has no problem

A county may have a lower percentage but still have a large number of residents living with dementia. Population size matters. A heavily populated county with a moderate prevalence rate may need more neurologists, caregivers, adult day services, transportation programs, and long-term care capacity than a smaller county with a higher percentage.

Prevalence and mortality are different measurements

A county with a high estimated prevalence is not automatically the county with the highest Alzheimer’s death rate. Prevalence measures how many people are living with a condition at a particular time. Mortality measures deaths. Diagnosis practices, access to care, cause-of-death reporting, population age, and survival can make the two maps look different.

The numbers describe 2020, not today

This may be the most important fine print. The estimates are a snapshot based on 2020 population characteristics. Communities change. People move. Populations age. Health systems expand or shrink. New treatments become available. Diagnostic practices evolve.

For current planning, county prevalence estimates should be considered alongside newer census information, local health department data, Medicare data, caregiver surveys, and health care capacity.

Why County-Level Alzheimer’s Data Matters

Statewide averages can hide enormous local differences. A state may look reasonably prepared on paper while particular counties struggle with long specialist wait times, caregiver shortages, limited transportation, or a lack of culturally appropriate dementia services.

County-level data allows public health leaders to ask more practical questions.

• Where are memory assessment and primary care services most needed?
• Which communities need more caregiver education and respite care?
• Where should bilingual or culturally tailored programs be expanded?
• Which counties may need more adult day programs, home health workers, or long-term care capacity?
• Where could earlier screening and cardiovascular risk reduction have the greatest community impact?

That level of detail can turn a national crisis into a local action plan. “Millions of Americans are affected” is an important message. “This county needs more caregiver support within driving distance” is a message that can change a budget.

What Families Can Do With This Information

County rankings are most useful when they encourage action rather than panic.

Families should pay attention to persistent changes in memory, judgment, language, behavior, navigation, or the ability to handle familiar daily tasks. Forgetting where the car keys are is common. Finding the keys in the freezer and having no idea how they arrived there deserves a different level of attention.

A medical evaluation can help identify whether symptoms may be related to Alzheimer’s, another form of dementia, medication effects, depression, sleep problems, vitamin deficiencies, thyroid disorders, or another condition. Some causes of cognitive symptoms can be treated, and even when a progressive dementia is diagnosed, earlier recognition can give families more time to discuss treatment, finances, transportation, safety, caregiving, and future preferences.

People can also work on factors associated with healthier aging. Managing blood pressure and diabetes, staying physically active, avoiding smoking, protecting hearing, maintaining social connections, and getting appropriate medical care are sensible steps for overall health as well as brain health. No lifestyle checklist can guarantee that Alzheimer’s will be prevented, and anyone promising a magical dementia-proof smoothie should probably be viewed with the same skepticism as a bridge for sale.

The Larger U.S. Alzheimer’s Picture Is Still Growing

The county map is only one piece of a rapidly expanding national challenge. In 2026, an estimated 7.4 million Americans age 65 and older were living with clinical Alzheimer’s dementia. The growing number of older adults means the absolute burden is expected to rise even if progress is made in reducing some risk factors.

That burden extends well beyond the person receiving the diagnosis. Alzheimer’s affects spouses who become full-time caregivers, adult children balancing jobs and medical appointments, grandchildren watching family roles change, health systems managing increasingly complex patients, and communities trying to build services quickly enough.

The counties at the top of the prevalence list should not be treated as curiosities in a national ranking. They are early warnings about the scale of planning many other communities may eventually need.

Experiences Behind the Map: What High Alzheimer’s Prevalence Can Feel Like

The following section describes a composite, illustrative family and community experience based on common challenges reported by people affected by dementia. It is not the story of one identifiable patient.

Imagine a family living in a county with one of the nation’s highest estimated Alzheimer’s prevalence rates. The experience probably does not begin with a dramatic movie scene. There is no thunderclap, no ominous violin, and usually no doctor appearing on the doorstep with a folder labeled “Important Plot Development.”

It may begin with small things.

A mother who has cooked the same holiday meal for 40 years suddenly cannot remember the order of the steps. A father who always paid the household bills receives a second late notice. An aunt calls her niece three times in one morning to ask the same question. Everyone notices, but everyone also has an explanation. She is tired. He is stressed. Everybody forgets things.

Months pass before the family schedules an appointment. The primary care office is busy. The nearest specialist may have a long waiting list. One adult child lives 20 minutes away; another lives in a different state. The person with memory problems insists nothing is wrong, which can be part of the disease but also sounds, to the family, like ordinary stubbornness.

Once a diagnosis arrives, the family discovers that diagnosis is not the finish line. It is more like being handed a map after the road has already become complicated.

Someone must keep track of medications. Someone starts attending medical appointments. Driving becomes a tense topic. The family discusses legal documents that everyone wishes they had completed five years earlier. A spouse quietly stops meeting friends because leaving the person with dementia alone no longer feels safe.

In a well-resourced community, families may find a memory clinic, caregiver support group, adult day program, transportation assistance, bilingual education, home health services, and respite care. In an underserved area, the same family may spend hours making phone calls and still hear variations of “We have a waiting list.”

This is where county-level Alzheimer’s data becomes more than an interesting map.

Suppose local health officials know that their county has a particularly high estimated prevalence among older residents. They can use that information to argue for more dementia training in primary care, additional caregiver programs, mobile services, community health workers, or educational campaigns designed for the languages and cultures of local residents.

For a Hispanic family, a bilingual navigator may make the difference between understanding a diagnosis and leaving an appointment confused. For an older Black caregiver who has experienced discrimination in health care, a trusted community organization may be more effective than another glossy brochure mailed from an unfamiliar institution. For a rural family, transportation may be as important as the specialist appointment itself.

The experience also changes over time. Early in the disease, a person may still manage many daily activities independently. Later, the family may need help with meals, bathing, wandering prevention, behavioral symptoms, nighttime supervision, and eventually round-the-clock care.

Caregivers often become experts without ever applying for the job. They learn which questions calm anxiety, how to redirect an argument, when not to correct a mistaken memory, and how to survive on coffee that has been reheated so many times it deserves its own medical chart.

But love does not eliminate exhaustion. Families need practical support, and the amount of support required is not evenly distributed across the country.

That is the human meaning behind the ranking. A prevalence estimate of 16.6% is not merely a percentage sitting neatly in a spreadsheet. It represents communities where a large share of older residents may be living with significant cognitive impairment and where thousands of relatives, friends, clinicians, home care workers, and neighbors may be adapting their lives around the disease.

The most useful response is therefore not to label a county an “Alzheimer’s hotspot” and move on. It is to ask what people in that county need next.

Conclusion: A County Map Should Be a Starting Point, Not a Stigma

The first nationwide county-level Alzheimer’s prevalence estimates revealed substantial geographic differences across the United States. Among larger older-adult populations, Miami-Dade County, Baltimore City, and Bronx County shared the highest estimated prevalence at 16.6%, while much of the top 10 was concentrated in the East and Southeast.

The findings highlight the influence of population age, longstanding racial and ethnic health disparities, chronic disease patterns, and unequal access to health and social resources. They also demonstrate why national and statewide averages are not enough. Alzheimer’s is experienced locally, in kitchens, clinics, workplaces, churches, senior centers, and homes where caregivers are trying to remember when they last had a full night’s sleep.

Most importantly, the rankings should not be used to stigmatize communities or predict an individual person’s future. Their greatest value is practical: helping leaders identify where earlier diagnosis, culturally responsive care, caregiver support, prevention programs, and health care resources may be needed most.

Note: The county rankings in this article refer to modeled prevalence estimates for 2020 that were first publicly reported in 2023. They should not be interpreted as a live 2026 ranking or as confirmed case counts for every resident. This content is for general educational purposes and is not a substitute for individualized medical advice or diagnosis.