Alzheimer's disease: an animated, cited guide

This page needs JavaScript for its animations. The outline and key answers are below, and every claim in the full version carries a numbered citation.

Not medical advice. Alzheimer's Companion is an educational synthesis of published literature. It does not replace a clinician.

What is in it

What Alzheimer's is Dementia versus Alzheimer's, who it affects, the numbers.
The brain that forgets Where it starts and how it spreads, stage by stage.
Amyloid, animated From one protein cut to a plaque, and the debate about it.
Tau and the tangle How a scaffold protein turns into a tangle and spreads.
Microglia and the lost synapse Inflammation, pruning, and the strongest link to memory loss.
Genes and inheritance APOE, the dominant families, Down syndrome, and what a test means.
Twenty years before symptoms The biomarker cascade, in order.
Stages and symptoms From no symptoms to severe dementia, function by function.
Diagnosis and biomarkers Criteria, scans, spinal fluid, blood tests and screening tools.
The differential Delirium, vascular, Lewy body, frontotemporal and reversible causes.
Cholinesterase inhibitors and memantine Inside the synapse, and what the benefit really is.
Anti-amyloid antibodies over time Lecanemab and donanemab over 18 months, ARIA and the debate.
Beyond memory Agitation, mood, psychosis and sleep, and the drug cautions.
Lowering the risk The 14 modifiable risk factors and what trials show.
Living with dementia and caregiving Planning, safety, caregivers and the end of life.
Nursing care Assessment, giving the medicines, communication, documentation.
Toward a cure The pipeline, prevention trials, and the evidence for each route.
History and people From Auguste Deter in 1901 to the antibodies.
Flashcards and mnemonics Flip cards by topic.
Quiz Questions with explanations.
Glossary Every term, searchable.
Sources Every reference behind the app.

Part 2 · Course and diagnosis

The differential

Not every memory problem is Alzheimer's. How fast it started and what came first are among the strongest clues. Watch eight typical courses unfold on the same clock, then click any row for details.

Time axis

Time

Typical patterns, schematic: higher line means better function. Solid line: thinking. Dashed line: the domain that leads (behaviour, gait or mood). Real people rarely follow a textbook course, and mixed causes are common.

The differential, condition by condition

Click a condition to open what else the sources say about it.

Condition	What points to it rather than Alzheimer's	Key tests and findings

Delirium or dementia?

Delirium is a medical emergency that can look like dementia, and it often happens on top of dementia. The Confusion Assessment Method (CAM) asks four questions. Switch the features on and off to see how the algorithm combines them.

Features present

Teaching illustration of the published algorithm, not a bedside tool. ²⁴⁸

Feature	Delirium	Typical Alzheimer's dementia
Onset	Acute: hours to days (CAM feature 1). ²⁴⁸	Insidious, over months to years. ³⁴⁷
Course	Fluctuates, often within a day. ²⁴⁸	A clear history of gradual worsening. ³⁴⁷
First domain	Inattention, a required CAM feature. ²⁴⁸	Usually recent memory. ^2,206
Arousal	Level of consciousness may be altered (CAM feature 4). ²⁴⁸	Dementia criteria require that delirium does not explain the symptoms. ³⁴⁷
Tools	CAM: under 5 minutes, 94 to 100% sensitivity and 90 to 95% specificity in validation. In people with dementia, one study found only 77% sensitivity. ^248,367	History from an informant, cognitive testing, then the workup in Diagnosis and biomarkers. ³⁰
Overlap	Delirium on top of dementia was reported in 22 to 89% of older people with dementia and linked to faster decline, institutional care and death. Fluctuating attention and arousal are also core features of Lewy body dementia. ^171,346

The reversible-causes workup

Reveal

Rates from a 2003 meta-analysis of 39 studies (5,620 people), scaled to 1,000 people. Positions are random.

Published guidance

Routine in the AAN parameter

Screening for depression, B12 deficiency and hypothyroidism, and a non-contrast CT or MRI, in the initial evaluation. This is a 2001 guideline. ²⁸⁴

Only when suspected

Syphilis serology when neurosyphilis is suspected. CSF or genetic testing is considered for atypical cases: onset before 65, rapid onset, or non-memory presentations. ^30,284

Medicines

A medication review. The heaviest cumulative use of strong anticholinergics, most commonly tricyclic antidepressants, first-generation antihistamines and bladder antimuscarinics, was associated with dementia (hazard ratio 1.54). ²⁰⁷

Sleep

Sleep-disordered breathing was associated with incident MCI or dementia in 298 older women (odds ratio 1.85), following low oxygen rather than broken sleep. ⁵³⁰

Gait first

When walking changes first, imaging looks for the enlarged ventricles and DESH pattern of normal-pressure hydrocephalus; a CSF tap test may follow. ³⁷³

A sudden change

A sudden worsening points to delirium and a search for medical and drug causes, even in someone already living with dementia. ^171,248