Around 57 million people worldwide were living with dementia as of 2021, according to the World Health Organization. That number is expected to nearly triple to roughly 153 million by 2050, driven largely by aging populations and population growth in low- and middle-income countries.
How Risk Changes With Age
Dementia is overwhelmingly a condition of older age, but the risk at any given age is lower than many people assume. Among U.S. adults aged 65 to 74, only about 1.7% have a dementia diagnosis. That climbs to 5.7% for those aged 75 to 84, and reaches 13.1% for people 85 and older. So even in the oldest age group, roughly seven out of eight people do not have dementia.
Dementia can also strike earlier. An estimated 3.9 million people between the ages of 30 and 64 are living with what’s called young-onset dementia. That works out to about 119 per 100,000 people in that age range, making it uncommon but far from rare. Young-onset cases are more likely to involve genetic factors and often take longer to diagnose because neither patients nor doctors are looking for dementia in a 50-year-old.
Women Are Affected More Often
Two-thirds of Americans living with Alzheimer’s disease are women. The biggest reason is simple: women live longer, and age is the strongest risk factor. But longevity doesn’t fully explain the gap. 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.
Genetics play a role in this disparity. The APOE4 gene variant, the strongest known genetic risk factor for late-onset Alzheimer’s, hits women harder. Carrying a copy of APOE4 raises dementia risk by about 81% in women compared to 27% in men. Researchers at Stanford have found preliminary evidence that estrogen can bind to DNA near the APOE gene, potentially influencing how much of the related protein gets produced. The loss of estrogen at menopause may be associated with higher Alzheimer’s risk decades later, though this connection is still being studied.
Lifestyle differences also contribute. Where people work, what they eat, how much they exercise, and how much air pollution they’re exposed to all vary systematically between men and women, and all have been linked to dementia risk. Interestingly, the pattern reverses for Lewy body dementia, the second most common type after Alzheimer’s, which affects roughly twice as many men as women.
Types of Dementia
Alzheimer’s disease accounts for the majority of dementia cases, typically estimated at 60% to 70% of all diagnoses. It involves a gradual buildup of abnormal proteins in the brain that destroy neurons, starting in areas responsible for memory.
Vascular dementia is the second most common form and results from reduced blood flow to the brain, often after strokes or from chronic damage to small blood vessels. Lewy body dementia causes visual hallucinations, movement problems, and fluctuating alertness alongside memory loss. Frontotemporal dementia tends to strike earlier, often between ages 45 and 65, and typically affects personality and behavior before memory. Many people have mixed dementia, where more than one type is present at the same time.
Where Dementia Is Growing Fastest
More than 60% of people with dementia live in low- and middle-income countries, and that share is expected to grow. These regions have rapidly aging populations but far fewer resources for diagnosis, treatment, and caregiving. In many countries, dementia goes undiagnosed entirely, meaning the true numbers are likely higher than official estimates suggest.
The projected jump from 57 million to 153 million cases by 2050 will not be evenly distributed. Countries in sub-Saharan Africa and parts of Asia face the steepest increases, in some cases seeing their dementia populations more than double in a single generation. High-income countries will also see significant growth, though improved cardiovascular health and higher education levels may partially offset the trend.
The Economic Weight of Dementia
Dementia is one of the costliest health conditions in the world. From 2020 to 2050, it is projected to cost the global economy roughly $14.5 trillion (in 2020 international dollars), equivalent to about 0.4% of annual global GDP. The vast majority of that cost is not hospital bills or medication. In lower-middle-income countries, informal care (family members providing unpaid support) accounts for more than 85% of the economic burden. Even in high-income countries, informal care makes up about 61% of total costs, with formal treatment and professional care covering the rest.
Diagnosis Is Changing
One reason dementia numbers may shift in coming years has nothing to do with the disease itself. New blood tests can now detect Alzheimer’s-related proteins years before symptoms appear. These tests are expected to become the standard of care once insurance coverage, particularly Medicare and Medicaid, catches up. If blood-based screening becomes routine, the number of people with a recorded dementia diagnosis could rise substantially, not because more people are getting sick, but because more cases are being caught. Earlier detection also opens the door to newer treatments that work best when started before significant brain damage has occurred.