Alzheimer’s Disease and Other Types of Dementia

What is dementia?

Dementia describes decline in memory, reasoning, communication, and behavior severe enough to affect daily function. It is an umbrella term with multiple causes. Global burden estimates exceed 55 million individuals, with millions of new cases annually.

Alzheimer’s disease

Alzheimer’s accounts for roughly 60–70% of dementia. Early symptoms often include recent memory loss and subtle executive dysfunction. Pathobiology features amyloid-β plaques and tau neurofibrillary tangles, leading to synaptic failure and neuronal loss. With progression, language, judgment, and independence decline.

Dementia with Lewy bodies (DLB)

DLB is linked to α-synuclein aggregates (Lewy bodies). Typical clues: vivid visual hallucinations, fluctuating attention, and REM sleep behavior disorder. Parkinsonian motor features (rigidity, bradykinesia, tremor) are common and complicate diagnosis.

Frontotemporal dementia (FTD)

FTD preferentially affects frontal and temporal lobes. Early stages emphasize personality/behavior change or language variants (primary progressive aphasias). Memory may be relatively preserved early. Onset can be younger (40s–50s).

Vascular dementia

Vascular dementia stems from cerebrovascular injury (infarcts, small-vessel disease). Clinical course may be stepwise after strokes and often features slowed processing and executive dysfunction. Risk mitigation includes controlling blood pressure, diabetes, lipids, and smoking cessation.

The bigger picture

Other etiologies include Parkinson’s disease dementia, Huntington’s disease, normal pressure hydrocephalus, autoimmune/inflammatory encephalitis, and potentially reversible causes (e.g., thyroid dysfunction, B12 deficiency, medication effects). Understanding subtype matters for counseling, management, and prognosis. Research advances—including disease-modifying therapies for AD—offer cautious optimism for slowing progression.

Key differences at a glance