Dementia is one of the most common neurological conditions in the world, affecting roughly 55 million people globally. That number is expected to more than triple by 2050, reaching an estimated 115 million. While dementia becomes far more likely with age, it is not an inevitable part of getting older, and the risk varies significantly depending on age, sex, ethnicity, and where you live.
How Risk Increases With Age
Age is the single strongest predictor of dementia. Among people in their early 70s, about 5% have dementia. That number jumps sharply in each subsequent decade: roughly 24% of people in their 80s live with some form of dementia, and among those 90 and older, the rate climbs to about 37%. This steep acceleration explains why dementia is becoming more common overall as populations age, even though the rate at any given age hasn’t necessarily increased.
Dementia before age 65, sometimes called young-onset dementia, is relatively rare but not as uncommon as many people assume. An estimated 3.9 million people worldwide between the ages of 30 and 64 are living with it. The risk rises steeply even within that range: prevalence jumps from about 1 per 100,000 people in the 30-to-34 age group to 77 per 100,000 among those aged 60 to 64.
Women Are Affected More Than Men
About two-thirds of people diagnosed with dementia are women. This isn’t simply because women live longer, though that plays a role. Incidence rates for men and women are nearly identical until the early 80s, then diverge significantly between ages 85 and 90. For Alzheimer’s disease specifically, the gap opens up around age 80. In one large study, 25% of women developed some form of dementia over the study period compared with about 19% of men.
Researchers are still working to fully explain this gap. Longer life expectancy accounts for part of it, but hormonal changes after menopause and differences in cardiovascular risk may also contribute.
Racial and Ethnic Disparities in the US
In the United States, dementia does not affect all populations equally. A large 2022 study found that Black Americans had a 54% higher rate of developing dementia compared to White Americans, even after adjusting for factors like education and income. Hispanic Americans had a 92% higher rate. These disparities likely reflect a combination of systemic factors: unequal access to healthcare, higher rates of conditions like diabetes and hypertension that raise dementia risk, and the long-term health effects of chronic stress and discrimination.
Types of Dementia and How They Break Down
Dementia is an umbrella term, not a single disease. Alzheimer’s disease is by far the most common form, accounting for an estimated 60% to 80% of all cases. It causes a gradual decline in memory, thinking, and reasoning as proteins build up abnormally in the brain.
The remaining cases are split among several other conditions:
- Vascular dementia accounts for 5% to 10% of cases and results from reduced blood flow to the brain, often after strokes or from chronic cardiovascular disease.
- Lewy body dementia makes up about 5% of cases and is characterized by visual hallucinations, movement problems similar to Parkinson’s, and fluctuating alertness.
- Frontotemporal dementia represents about 3% of cases in people 65 and older but roughly 10% in those diagnosed before 65. It tends to affect personality, behavior, and language more than memory in its early stages.
- Parkinson’s-related dementia accounts for about 3.6% of cases.
Many people have “mixed dementia,” where two or more types occur simultaneously, most commonly Alzheimer’s combined with vascular dementia. This overlap is especially common in the oldest age groups and can make diagnosis more complicated.
Most Cases Go Undiagnosed
One of the most striking statistics about dementia is how many people living with it don’t know they have it. A meta-analysis pooling data from studies around the world found that nearly 62% of dementia cases in the community are undetected. That means for every person who has been diagnosed, roughly 1.6 others are living with unrecognized cognitive decline.
This matters for several reasons. People without a diagnosis miss out on treatments that can help manage symptoms, can’t plan for future care needs, and may be at greater risk for preventable complications like medication errors, falls, or financial exploitation. The gap is widest in low- and middle-income countries, where access to specialists and diagnostic tools is more limited, but it remains significant even in wealthy nations.
Where Dementia Is Growing Fastest
More than two-thirds of people with dementia currently live in low- and middle-income countries, and that share is expected to grow. By 2050, an estimated 65% of the global dementia burden will be concentrated in those regions, up from 18% in 2019. The driving forces differ by region: in wealthier countries, the primary factor is aging populations, while in lower-income countries, population growth is the bigger contributor.
This uneven distribution creates a particular challenge because the countries where dementia is growing fastest are often the least equipped to provide diagnosis, treatment, and long-term care. Many of these nations have fewer than one neurologist per million people, making early detection and management extremely difficult.
Putting the Numbers in Perspective
If you’re in your 60s or younger, the absolute risk of having dementia right now is low. If you’re in your 70s, roughly 1 in 20 people your age is affected. By the late 80s, it’s closer to 1 in 4. These are averages, and individual risk depends heavily on factors you can influence: cardiovascular health, physical activity, social engagement, hearing loss management, and education all play a role. Current estimates suggest that up to 40% of dementia cases worldwide are linked to modifiable risk factors.
Dementia is common enough that most families will encounter it in some form. But it is not a certainty, and the majority of older adults, even those in their 80s, do not develop it.