Types of Dementia: Why the Distinction Matters

Dementia describes a syndrome — cognitive decline severe enough to interfere with independent daily function — caused by any of several underlying diseases. Treating it as one condition obscures differences that matter clinically.

Alzheimer's disease

The most common cause. Typically begins with difficulty forming new memories — recent conversations and events — while older memories and procedural skills are relatively preserved early on. Progression is usually gradual, with language, visuospatial ability and executive function affected as it advances.

The pathology involves amyloid plaques and tau tangles, and biomarker testing has become increasingly relevant to diagnosis in specialist settings.

Vascular dementia

Caused by reduced blood supply to the brain, from stroke, multiple small strokes, or small vessel disease. Presentation varies with what is damaged, but executive function, processing speed and attention are often affected earlier and more prominently than memory.

Progression can be stepwise — relatively stable periods with sudden declines — rather than steadily gradual, though small vessel disease can produce gradual change.

This is the type where the modifiable risk factors discussed throughout this site are most directly relevant: blood pressure, diabetes, smoking, cholesterol, atrial fibrillation.

Lewy body dementia

Associated with alpha-synuclein deposits. Distinctive features can include marked fluctuation in alertness and cognition, recurrent detailed visual hallucinations, parkinsonian motor symptoms, and REM sleep behaviour disorder — acting out dreams physically, which can precede other symptoms by years.

Frontotemporal dementia

Affects the frontal and temporal lobes and tends to present at younger ages than other types, often between the fifties and sixties. Memory may be relatively preserved early, which contributes to delayed diagnosis.

Presentations divide broadly into a behavioural variant — marked personality change, disinhibition, loss of empathy, apathy, compulsive behaviours — and language variants affecting speech production or word comprehension.

Because early symptoms can look like a psychiatric condition or a midlife crisis, people are frequently misattributed before the correct diagnosis is reached.

Mixed pathology

Post-mortem studies have consistently found that many people, particularly older ones, have more than one pathology present — most commonly Alzheimer's and vascular changes together. Mixed pathology is common rather than exceptional, which is one reason clinical presentations do not always sort neatly into categories.

Conditions that can mimic dementia

Several conditions can produce similar pictures and have different management:

• Depression, discussed separately
• Delirium, which is acute and urgent
• Normal pressure hydrocephalus, classically with gait disturbance, urinary symptoms and cognitive change, and potentially treatable surgically
• Vitamin B12 deficiency, thyroid dysfunction, and other metabolic causes
• Medication effects
• Chronic subdural haematoma, sometimes after a minor head injury

Why the specific diagnosis matters

• Medication safety differs, most sharply with Lewy body dementia
• Available treatments differ by type
• Expected progression differs, which affects planning
• Which symptoms to anticipate differs, which affects caregiver preparation
• Some causes are treatable and should not be missed

Getting the right assessment

Reaching a specific diagnosis generally requires specialist involvement — neurology, geriatric medicine, psychiatry of old age — with detailed history, cognitive testing, blood work, and imaging where indicated. It is worth asking which type is suspected and on what basis, rather than accepting a general label.

Nothing on this page is a basis for self-diagnosis. Symptom lists overlap substantially, and distinguishing between these requires clinical assessment.