Alzheimer’s disease is remarkably common. An estimated 7.2 million Americans aged 65 and older are living with Alzheimer’s dementia in 2025, making it the most widespread form of dementia in the country and the seventh leading cause of death. Globally, about 57 million people had dementia as of 2021, and Alzheimer’s accounts for 60 to 70 percent of those cases.
Risk by Age Group
Alzheimer’s is rare in younger age groups and becomes sharply more common with each decade of life. Among adults aged 65 to 74, about 1.7% have a dementia diagnosis. That number jumps to 5.7% for people aged 75 to 84, and climbs to 13.1% for those 85 and older. Roughly 1 in 9 Americans over 65 has Alzheimer’s.
These figures come from self-reported diagnoses, which means they likely undercount the true number. Many people in the earliest stages haven’t been evaluated yet or don’t realize their symptoms point to Alzheimer’s rather than normal aging.
Why Women Are Affected More Often
Two-thirds of Americans living with Alzheimer’s are women. The biggest reason is straightforward: women live longer than men, so more women reach the highest-risk age groups. There are more than twice as many women over 90 as men, for instance.
But longevity isn’t the whole story. At any given age, women appear slightly more likely to develop Alzheimer’s than men, at a ratio of roughly three women for every two men. The strongest known genetic risk factor for late-onset Alzheimer’s, a gene variant called APOE4, raises dementia risk by 81% in women but only 27% in men. Researchers at Stanford have found preliminary evidence that estrogen may directly influence how this gene behaves, which could help explain why the risk gap between sexes exists. Lifestyle differences between men and women, including differences in occupation, diet, exercise, and environmental exposures, have also been linked to dementia risk and likely play a role.
Racial and Ethnic Disparities
Alzheimer’s does not affect all populations equally. Black Americans are roughly 1.5 to 2 times as likely as white Americans to develop Alzheimer’s and related dementias. Research from the National Institute on Aging points to higher rates of hypertension and diabetes among Black participants as potential contributing factors, since both conditions are established risk factors for dementia. Less is known about prevalence in Latino and other underrepresented populations, partly because most large studies have focused on comparisons between Black and white participants.
A Massive Underdiagnosis Problem
The numbers above almost certainly understate reality. Globally, an estimated 75% of all dementia cases go undiagnosed. That translates to roughly 41 million people worldwide living with dementia who have never received a formal diagnosis. In low- and middle-income countries, the undiagnosed rate reaches as high as 90%.
Even in wealthier nations, diagnosis rates are low. The World Health Organization’s global action plan set a goal for countries to diagnose at least 50% of expected dementia cases, but data from Alzheimer’s Disease International suggests that high-income countries are diagnosing only about 25%. Early symptoms like memory lapses, difficulty with familiar tasks, and confusion about time or place are often dismissed as normal aging by patients, families, and sometimes physicians.
The Numbers Are Growing Fast
Alzheimer’s prevalence is climbing as populations age worldwide. The Alzheimer’s Association estimates that 7.4 million Americans aged 65 and older will be living with Alzheimer’s in 2026, up from 7.2 million in 2025. Globally, dementia cases are projected to nearly triple, reaching an estimated 152.8 million by 2050. This growth is driven primarily by longer lifespans and the aging of large population cohorts, particularly baby boomers in the United States.
The Economic Scale of the Disease
The sheer number of people affected translates into staggering costs. The total economic burden of Alzheimer’s and related dementias in the United States is expected to reach $781 billion in 2025. Medical and long-term care alone will cost $232 billion, with $52 billion of that coming directly out of patients’ and families’ pockets. Medicare covers about $106 billion, and Medicaid another $58 billion.
But the financial toll extends well beyond hospital bills and medications. Family members and friends provide an estimated 6.8 billion hours of unpaid care each year, valued at $233 billion. Some caregivers reduce their work hours or leave jobs entirely, resulting in $8.2 billion in lost earnings. The largest share of the total cost, $302 billion, reflects the decline in quality of life for patients themselves, a factor that most cost estimates overlook entirely.