7 Common Causes of Dementia: A Topline Review
The brain changes that lead to cognitive and behavioral changes referred to as dementia have multiple potential etiologies; not all dementia is Alzheimer disease.
For the 7 most common causes of dementia, the slideshow that follows summarizes
1. The associated brain changes
2. The estimated percentage of cases of dementia the cause is responsible for
3. Symptoms of the dementia
1. The associated brain changes
2. The estimated percentage of cases of dementia the cause is responsible for
3. Symptoms of the dementia
The hallmark of brain changes in Alzheimer disease is the accumulation of β‐amyloid outside neurons and twisted strands of tau inside.
Alzheimer disease is responsible for approximately 60% to 80% of dementia, making it the most common cause.
Symptoms of Alzheimer disease progress through 3 identifiable stages with the earliest stage characterized by difficulty remembering recent conversations, names or events, apathy, depression.
In dementia caused by cerebrovascular disease, or vascular dementia, blood vessels in the brain are damaged and/or brain tissue is injured from lack of blood, oxygen, nutrients
Vascular dementia alone accounts for 5% to 10% of people with the condition; most adults with dementia show brain changes of both cerebrovascular and Alzheimer disease
Early symptoms of dementia with cerebrovascular disease as the cause include slowed thoughts, impaired ability to make decisions, plan, organize and memory may also be affected
Brain changes in frontotemporal degeneration (FTD) are caused by neuronal death in the front and temporal lobes of the brain, causing the organ to shrink.
FTD affects individuals between the ages of 45 and 60 years; research suggests FTD accounted for ~3% of cases in studies of adults ≥65 yrs and ~10% of cases in those <65 yrs
Symptoms of FTD in the early stages include marked changes in personality, behavior and/or difficulty producing or comprehending language; memory is typically spared in the early stages of the disease
Lewy bodies are abnormal aggregations of neuronal α‐synuclein; dementia can result when aggregation develops in the cortex, resulting in dementia with Lewy bodies (DLB)
Dementia with Lewy bodies affects approximately 5% of older individuals with dementia; most people with this form of dementia also show signs of Alzheimer disease
Early symptoms of Lewy body dementia include sleep disturbances, well‐formed visual hallucinations, visuospatial impairment; symptoms may change dramatically during a day or from day to day
Hippocampal sclerosis is the shrinkage and hardening of tissue in the hippocampus of the brain, a key location for memory formation; brain changes seen in HS are often accompanied by accumulation of the misfolded protein TDP‐43
Hippocampal sclerosis is observed in ~ 3% to 13% of people with dementia; HS often occurs with other causes of dementia; ~0.4% to 2% of dementia cases are due to HS alone
Memory loss is the most pronounced symptom of HS; HS is often misdiagnosed as Alzheimer disease; the disease is the most common cause of dementia in individuals aged ≥85 yrs
In limbic‐predominant age‐related TDP‐43 encephalopathy (LATE) TDP‐43 accumulates in the brain where it is a naturally occurring protein that supports neurogenesis; accumulation of TDP-43 in the limbic system, affects memory, emotion, behavior, and mood
The proportion of LATE-related cases of dementia is currently unclear; autopsy studies of more >6,000 people found that 40% had the TDP‐43 deposits characteristic of LATE and that it was associated with memory/thinking deficits in ~25% of those
Symptoms of LATE are similar to symptoms of Alzheimer disease but begin later (≥75 yrs), are milder/worsen more slowly; there are fewer cognitive and functional problems in early stages than with AD
Brain changes of Parkinson disease are the result of clumps of α‐synuclein in the substantia nigra; they are thought to cause degeneration of dopaminergic cells; α‐synuclein typically accumulates in the cortex as PD progresses
Approximately 3.6 of dementia cases may be the result of Parkinson disease and 24.5% of people with PD developed dementia
Symptoms common in Parkinson disease include problems with movement (slowness, rigidity, tremor and changes in gait); cognitive symptoms may develop later in the disease, typically years after movement symptoms
Source: Alzheimer's Association. 2025 Alzheimer’s disease facts and figures. Alzheimer’s Dement. 2025;21:e70235. doi: 10.1002/alz.70235
Dementia is not a single disease and not all dementia is Alzheimer disease, a common misconception in the general public and likely among patients in your practice. The clinical syndrome called dementia is characterized by progressive decline in one or more cognitive domains, ie, memory, executive function, language, visuospatial ability, and behavior, that is sufficient to cause difficulty with daily functioning. The underlying neuronal loss and dysfunction in nerve transmission are the result of neurodegeneration and/or cerebrovascular injury.
The pathophysiology, symptomatology, and progression of dementia will vary by individual and by the underlying etiology. Mixed pathologies are common and particularly in older adults, but most people will present with symptom patterns that are characteristic of a major dementia subtype.
The slide show above, based on the Alzheimer's Association report, 2025 Alzheimer's disease facts and figures, summarizes the brain changes, estimated prevalence, and the symptoms for dementia resulting from 7 common etiologies:
- Alzheimer disease
- Cerebrovascular disease
- Frontotemporal degeneration (FTD)
- Hippocampal sclerosis (HS)
- Lewy body disease
- Limbic‐predominant age‐related TDP‐43 encephalopathy (LATE)
- Parkinson disease
Dementia is not a normal part of aging; although cognitive changes are expected in later adulthood, they are typically more subtle than the disruptive deviations of dementia.
The progression of dementia, across all types, is typically described in 3 stages: early (mild), middle (moderate), and late (severe). Changes in the early stage are generally subtle, especially in memory or language, and often attributed to the aging process. As the neurodegenerative process continues, individuals need increasing assistance with instrumental and eventually basic activities of daily living. Behavioral and psychiatric symptoms, such as apathy, depression, disinhibition, and even delusions, may emerge, and in late-stage disease, patients often lose functional independence entirely.
Symptoms do frequently overlap but a precise diagnosis is essential as ongoing treatment, both pharmacologic and behavioral, may may have differential efficacy depending on the underlying etiology.
