What is the difference between Alzheimer disease and dementia?

Understanding the Difference Between Alzheimer's Disease and Dementia

Dementia is a clinical syndrome—not a specific disease—while Alzheimer's disease is the most common pathological cause of that syndrome. 1

Dementia: The Clinical Syndrome

Dementia is diagnosed when cognitive or behavioral symptoms interfere with the ability to function at work or in usual daily activities, represent a decline from previous functioning, are not explained by delirium or major psychiatric disorder, and involve impairment in at least two cognitive domains. 1, 2

The five cognitive domains that may be affected include:

• Memory impairment (learning and recall of recent information) 1
• Executive dysfunction (impaired reasoning, judgment, problem-solving) 1
• Visuospatial impairment (inability to recognize faces or objects, spatial disorientation) 1
• Language dysfunction (word-finding difficulties, speech errors) 1
• Personality and behavioral changes (apathy, mood fluctuations, loss of empathy) 1

The key distinguishing feature of dementia versus mild cognitive impairment is significant interference with daily functioning—dementia requires that cognitive deficits prevent performance of instrumental or basic activities of daily living. 1, 2

Alzheimer's Disease: One Specific Cause

Alzheimer's disease is a specific neurodegenerative pathological process characterized by beta-amyloid plaques and tau neurofibrillary tangles that causes 50-70% of all dementia cases. 1, 3

The Relationship Explained

Think of it this way:

• Dementia = the symptom complex (like "fever" or "heart failure")
• Alzheimer's disease = one specific underlying cause (like "pneumonia" causing fever, or "coronary artery disease" causing heart failure)

The terms 'MCI' and 'dementia' do not indicate a particular etiology—they may result from vascular disease, Parkinson's disease, Lewy body accumulation, major depressive disorder, sleep disorders, substance abuse, polypharmacy, or other causes instead of, or in addition to, Alzheimer's disease pathology. 1

Other Major Causes of Dementia

Besides Alzheimer's disease, dementia can be caused by:

• Vascular dementia (from strokes or cerebrovascular disease) 1
• Dementia with Lewy bodies 1
• Frontotemporal dementia (behavioral variant or language variants) 1
• Parkinson's disease dementia 1
• Mixed pathologies (often Alzheimer's combined with cerebrovascular disease) 3, 4

Clinical Presentation of Alzheimer's Disease Dementia

When Alzheimer's disease causes dementia, the typical presentation includes:

• Amnestic syndrome (prominent difficulty learning and recalling recent information) as the most common initial feature 1, 5
• Insidious onset with gradual progression over months to years 2
• Progressive impairment in additional cognitive domains beyond memory (executive function, language, visuospatial skills) 1
• Eventual inability to perform instrumental activities of daily living (managing finances, medications, cooking) followed by basic activities (bathing, grooming, eating) 1

However, memory impairment is NOT always the primary deficit—nonamnestic presentations of Alzheimer's disease include language-predominant, visuospatial-predominant, or executive dysfunction-predominant variants. 1, 2

Critical Diagnostic Distinction

The diagnosis of probable Alzheimer's disease dementia should NOT be applied when there is evidence of:

• Substantial cerebrovascular disease (stroke temporally related to cognitive decline, multiple infarcts, severe white matter disease) 1
• Core features of dementia with Lewy bodies 1
• Prominent features of frontotemporal dementia variants 1
• Another concurrent neurological disease or medical condition that could substantially affect cognition 1

Common Pitfall to Avoid

Do not use "Alzheimer's" and "dementia" interchangeably in clinical documentation or patient communication. Dementia is the syndrome; Alzheimer's disease is one specific cause. A patient may have dementia from vascular disease, Lewy body disease, or other etiologies without having Alzheimer's disease pathology. 1 Conversely, not all patients with Alzheimer's disease neuropathologic changes exhibit symptoms of dementia—some remain cognitively normal. 4

Accurate etiologic diagnosis matters increasingly because disease-modifying treatments target specific pathologies (e.g., anti-amyloid therapies for Alzheimer's disease would not benefit someone whose dementia is caused by frontotemporal degeneration or vascular disease). 5, 3