Alzheimer’s disease is remarkably common. An estimated 7.2 million Americans age 65 and older are living with Alzheimer’s dementia in 2025, which works out to about 1 in 9 people in that age group. Globally, roughly 57 million people were living with dementia as of 2021, and Alzheimer’s accounts for 60% to 80% of all dementia cases.
Risk by Age Group
Age is the single biggest factor in how likely someone is to develop Alzheimer’s, and the numbers climb steeply with each decade. Among adults 65 to 74, just 1.7% have a dementia diagnosis. That jumps to 5.7% for those 75 to 84, and reaches 13.1% for people 85 and older. The pattern is straightforward: the longer you live, the higher the odds.
That said, Alzheimer’s is not exclusively a disease of old age. Early-onset Alzheimer’s, which strikes before age 65, makes up about 5% to 6% of all cases. Estimates from the mid-2000s placed the number of Americans with early-onset Alzheimer’s between 220,000 and 640,000. These cases often progress differently and can be harder to recognize because neither patients nor their doctors are looking for dementia in someone in their 40s or 50s.
Women Are Affected More Often
About two-thirds of Americans with Alzheimer’s are women. The most obvious explanation is that women live longer, giving the disease more time to develop. But longevity alone may not tell the whole story. A large twin study found that 15.8% of women developed Alzheimer’s compared to 10.2% of men. Researchers have proposed several additional explanations: biological differences in how the disease progresses, the possibility that men with cardiovascular risk factors die before dementia can set in, and potential differences in how much brain pathology is needed before symptoms appear.
Racial and Ethnic Disparities
Alzheimer’s does not affect all communities equally. African Americans and Hispanic Americans consistently show higher rates of both dementia and Alzheimer’s compared to non-Hispanic white Americans. One large longitudinal study of elderly New York City residents found that the incidence rate for Black older adults was 4.2% per person-year and 3.8% for Caribbean Hispanic participants, both significantly higher than the rate for non-Hispanic white participants.
The reasons are complex and intertwined. Higher rates of hypertension and diabetes in Black and Hispanic communities contribute to vascular damage that raises Alzheimer’s risk. Traumatic brain injury, another known risk factor, is also more common in minority populations. Beyond biology, systemic factors play a role: disparities in education quality, literacy, and occupational opportunity may reduce what researchers call “cognitive reserve,” the brain’s ability to compensate for damage. These are population-level patterns shaped by decades of unequal access to healthcare, nutrition, and education.
Many Cases Go Undiagnosed
A significant number of people with Alzheimer’s don’t know they have it. Research in developed countries suggests that roughly half of all dementia cases are never formally diagnosed. One cross-sectional study found that only 42% of participants who met diagnostic criteria for dementia had actually received a prior diagnosis. When researchers looked more closely at people with close family informants who could provide detailed history, that number dropped to 37%.
Most undiagnosed cases are mild. About three-quarters of people with undiagnosed dementia in the study had mild symptoms or less. This makes a certain kind of sense: early memory lapses are easy to dismiss as normal aging, and many people never bring them up with a doctor. But it also means a large number of people are missing the window when interventions, support services, and planning could do the most good.
The Numbers Are Expected to Nearly Triple
The aging of the baby boomer generation is set to transform Alzheimer’s from a common disease into one of the defining public health challenges of the next few decades. The number of Americans with Alzheimer’s dementia is projected to nearly triple by 2050, reaching an estimated 13.8 million people. That growth is driven almost entirely by demographics: more people living into their 80s and 90s means more people crossing into the age range where risk is highest.
Globally, the picture is even more striking. Over 60% of people with dementia live in low- and middle-income countries, where diagnostic resources and care infrastructure are often limited. As populations age worldwide, the gap between the number of people who need dementia care and the systems available to provide it will only widen.