Most people picture dementia as something that happens in old age, maybe the late 70s or 80s. That picture is accurate for the majority of cases. But for a meaningful number of people, the first symptoms show up in their 50s, their late 40s, or occasionally even earlier. This is called early-onset dementia, sometimes referred to as young-onset dementia, and it comes with a distinct set of challenges that are worth understanding separately.
How Common Is It?
Early-onset dementia is defined as dementia with symptom onset before the age of 65. It is less common than late-onset dementia, but it is not rare.
A 2021 meta-analysis published in JAMA Neurology, which reviewed 74 studies and data from 2.8 million adults between the ages of 30 and 64, estimated that approximately 119 per 100,000 people in that age group have young-onset dementia. That translates to roughly 3.9 million cases worldwide. A more recent 2025 study published in European Journal of Neurology, drawing on Global Burden of Disease data from 204 countries, estimated that early-onset Alzheimer’s disease and related dementias affected 7.75 million people between the ages of 40 and 64 in 2021, more than double the 3.67 million cases recorded in 1990.
These numbers are not insignificant. Early-onset dementia is uncommon enough that clinicians sometimes miss it, but common enough that most families will eventually know someone affected by it.
What Types of Dementia Are Most Common in Younger People?
The same disease categories that cause late-onset dementia also cause early-onset dementia, but the distribution looks a little different.
Alzheimer’s disease is still the most prevalent type, accounting for roughly 48% of early-onset cases in population-based studies. However, frontotemporal dementia (FTD) makes up a significantly larger share in younger populations than it does in older ones. Behavioral variant FTD, which primarily affects personality and social behavior rather than memory in its early stages, is one of the most common causes of dementia in people under 60. Vascular dementia is also present, and Lewy body dementia and other less common types account for the rest.
There is also a genetic dimension that is more prominent in early-onset cases. A small percentage of early-onset Alzheimer’s disease is caused by rare, inherited gene mutations (in the APP, PSEN1, or PSEN2 genes) that virtually guarantee the disease will develop, often in someone’s 40s or 50s. This is distinct from the APOE e4 variant, which raises risk but does not cause the disease on its own. Genetic counseling is an important consideration for anyone with a family history of early-onset dementia.
Why Is It Harder to Diagnose
One of the most consistent findings in the research on early-onset dementia is that the path to diagnosis is longer and more difficult than it is for older adults. A 2025 retrospective study published in Biomedicines analyzing 191 patients with young-onset dementia found significant delays between symptom onset and formal diagnosis, driven by a combination of atypical presentations and clinicians not initially considering a neurodegenerative cause in someone relatively young.
A separate review published in Alzheimer’s & Dementia found that the diagnostic process for young-onset dementia is commonly marked by misdiagnosis. Because early-onset dementia often presents differently than the textbook picture, patients may first be told they have depression, anxiety, a psychiatric disorder, burnout, or thyroid problems. One published case report describes a patient whose first symptoms appeared in his early 40s and who spent a decade being treated for epilepsy before finally receiving a correct diagnosis.
A few factors make early-onset dementia particularly easy to miss. First, physicians are less likely to consider dementia when a patient is 50 than when they are 80, so cognitive symptoms in a younger person may be attributed to other causes. Second, early-onset dementia more frequently presents with non-memory symptoms first, particularly in frontotemporal dementia, where the initial signs may be personality changes, poor judgment, or unusual behavior rather than forgetting things. Third, the person themselves is often still working, raising children, and engaged in complex daily activities, which can mask deficits that would be more visible in an older person with fewer cognitive demands.
The Practical Impact on Families
A dementia diagnosis at 55 or 58 creates challenges that are simply not present when the same diagnosis comes at 80. These deserve to be named honestly.
Employment. The person is likely still in the middle of a career. Cognitive changes may first show up as job performance problems before anyone recognizes them as medical. Navigating disability benefits, disclosing a diagnosis to an employer, and planning for early retirement are all issues that come up immediately and often unexpectedly.
Financial and legal planning. A person diagnosed at 58 may have 15 or 20 years of disease progression ahead of them, during which their care needs will increase substantially. Financial planning, establishing power of attorney, and making decisions about long-term care become urgent in a way that is emotionally difficult when the person is still relatively young and functional.
Children at home. Many people diagnosed with early-onset dementia still have children living at home or young adult children who are affected by watching a parent decline at an age when they did not expect to face that. The caregiving burden often falls on a spouse who is also still working, which creates a layer of strain that families of late-onset dementia patients may not experience in the same way.
Care system mismatch. Most dementia care resources, support groups, day programs, and memory care facilities are designed with older adults in mind. A 57-year-old with dementia may be physically capable, socially aware enough to recognize they are out of place, and have different needs than the typical resident or participant. Finding appropriate care and community can be genuinely difficult.
What Families Should Know
If you suspect early-onset dementia in someone you love, the most important step is getting to a specialist. A neurologist or neuropsychologist with experience in young-onset dementia can conduct the cognitive testing, brain imaging, and where appropriate, cerebrospinal fluid or blood biomarker testing that is needed to establish a diagnosis. Primary care physicians are an appropriate starting point, but early-onset dementia often warrants referral to a memory disorder clinic or academic medical center.
Given the diagnostic delays documented in the research, persistence matters. If symptoms are being attributed to stress, depression, or normal aging but something still feels wrong, it is reasonable to ask for further evaluation.
It is also worth knowing that several genetic testing options exist for families with a strong history of early-onset dementia. Genetic counselors, often available through major academic medical centers, can help families understand what those tests mean and navigate the emotional complexity of having or not having that information.
Early-onset dementia is a different experience than late-onset dementia in some important ways, but it is the same disease process. The science, the staging frameworks, and the caregiving principles discussed in other resources apply equally. The difference is mostly in the context surrounding the diagnosis, and in many ways that context makes it harder. Understanding that is a reasonable place to start.
If you are new to understanding how dementia progresses over time, our post on the 7 Stages of Dementia breaks down the Global Deterioration Scale in plain language and explains what families can expect at each stage, regardless of when the diagnosis came.
Have questions about memory care for a loved one?
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Sources
● Hendriks S, et al. Global Prevalence of Young-Onset Dementia: A Systematic Review and Meta-analysis. JAMA Neurology. 2021;78(9):1080-1090.
● Zhang Z, et al. Global, Regional, and National Burden of Early-Onset Alzheimer’s Disease and Other Dementias in Young Adults Aged 40-64 Years, 1990-2021. European Journal of Neurology. 2025.
● Rivas J, et al. Young-Onset Dementia: Clinical Findings and Factors That Delay Early Diagnosis. Biomedicines. 2025;13(11):2793.
● Hendriks S, et al. Global Incidence of Young-Onset Dementia: A Systematic Review and Meta-analysis. Alzheimer’s & Dementia. 2022;18(12):2455-2468.
● Strikwerda-Brown C, et al. The Road to Young-Onset Dementia Diagnosis: Findings from the Joint Solutions Project. Alzheimer’s & Dementia. 2025.
● Alzheimer’s Association. 2024 Alzheimer’s Disease Facts and Figures. Alzheimer’s & Dementia. 2024.