F00 — Dementia in Alzheimer's disease

What is this category?

F00 is a category for dementia in which the clinical picture, course, and (where available) investigation findings are typical of Alzheimer's disease, with no evidence of another cause that would better explain the decline. It is the anchor category of the F00-F09 block: most other categories in the block exist to describe presentations that resemble dementia but differ in course (F01, F05), breadth of impairment (F04), or an identified alternative cause (F02).

Core diagnostic concept

The classification question F00 answers is not "is this person forgetful?" but "is there an acquired, global decline across multiple cognitive domains — not just memory — that has developed gradually, occurs with clear consciousness, and is not better explained by a vascular event, another specific brain disease, or a reversible acute cause?" Dementia in this classification is a syndrome defined by its breadth and course, not by memory loss alone.

Key diagnostic features

Decline across multiple cognitive domains

Memory impairment (especially for new information) together with decline in at least one other domain — language, praxis, executive function, or visuospatial skill — sufficient to interfere with everyday activities.

Insidious onset and gradual progression

Symptoms typically develop slowly over months, with a course of continuing decline rather than abrupt onset or a stepwise pattern.

Clear consciousness

Alertness and basic attention are preserved, at least until very late stages — this is the single most important feature separating dementia from delirium.

Decline from a previous level of functioning

A genuine change from the person's own earlier baseline, not simply a normal age-related slowing that leaves independence intact.

Absence of a better alternative explanation

No clinical or historical evidence that the decline is better accounted for by a specific other disease (F02), a vascular pattern (F01), or a reversible confusional state (F05) once these are actively considered.

Behavioural and psychological changes, often later

Apathy, irritability, disinhibition, or psychotic-quality symptoms can accompany the cognitive decline, particularly as the illness progresses, but are not required for an early diagnosis.

How to weigh evidence

These learning labels are teaching aids, not official ICD-10 terminology (see Sources and Method).

• supports A gradual, roughly year-long decline in memory and word-finding, with preserved alertness and no history of stroke.
• consistent not decisive The person is elderly. Age alone is a risk factor, not evidence of dementia.
• raises alternative A sudden onset of confusion over two days during a hospital admission for infection.
• contradicts or weakens Impairment confined to memory alone, with language, praxis and executive function all intact on testing.
• missing and necessary to ask Whether the decline began abruptly after a stroke or evolved gradually with no such event.

Duration and course

Minimum duration: A period of decline is expected to be evident over at least six months for confident classification as dementia, distinguishing it from an acute confusional state.

Course: Course in Alzheimer's disease is typically gradual and continuously progressive, without the abrupt steps or plateaus characteristic of vascular dementia and without the day-to-day or hour-to-hour fluctuation characteristic of delirium.

Included presentations

• A gradual, multi-domain cognitive decline with preserved alertness, no vascular events, and no other identified causative disease.
• Presentations with accompanying behavioural or mild psychotic-quality features, provided the core gradual, multi-domain decline pattern is present.
• Cases where investigations (where described) are consistent with, though not required to formally confirm, an Alzheimer-type process.

Exclusions and distinguishing presentations

Four-character subtypes (orientation)

A learner should not assign early- versus late-onset subtypes from age alone without checking the actual course and pattern of impairment. Subtype classification is taught here for orientation only and is not separately assessed in this pilot.

F00.0 — Dementia in Alzheimer's disease with early onset

Onset before age 65, often with a more rapid course and more prominent early language/praxis involvement. (taught for orientation only, not separately assessed in this pilot)

F00.1 — Dementia in Alzheimer's disease with late onset

Onset at or after age 65, typically with a slower course and memory impairment predominating early. (taught for orientation only, not separately assessed in this pilot)

F00.2 — Dementia in Alzheimer's disease, atypical or mixed type

Features do not clearly fit the early- or late-onset pattern, or a mixed Alzheimer's/vascular picture is present. (taught for orientation only, not separately assessed in this pilot)

External causes to check first

Categories in this block require that the disturbance is not better explained by another external cause listed below. These short capsules are reminders, not full teaching modules.

Common learner errors

• Common mistake: Treating old age itself as an explanation for cognitive decline

Worked example — using course and consciousness together

A 74-year-old retired teacher has, over the past year, become increasingly forgetful of recent conversations, repeats questions, and now struggles to manage her own finances — tasks she previously handled without difficulty. Her family describes the change as gradual, with no single triggering event. She remains alert and attentive throughout the day, has no history of stroke or head injury, and a recent physical examination and basic blood tests were unremarkable. There is no reported low mood.

1. Step 1 — Check breadth: the decline spans memory and at least one instrumental activity of daily living (managing finances), not memory alone, satisfying the multi-domain requirement.
2. Step 2 — Check course: the change has developed gradually over about a year, without a stepwise or sudden pattern, weighing against F01 and F05.
3. Step 3 — Check consciousness: she remains alert and attentive throughout, which weighs strongly against delirium (F05).
4. Step 4 — Check for an alternative cause: no stroke, no other identified disease process, and blood tests are unremarkable, weakening F01 and F02; no reported mood disturbance weakens a depressive pseudodementia explanation.
5. Conclusion — The presentation is best classified as F00, supported by gradual multi-domain decline with preserved consciousness and no identified alternative cause, while the boundary against F01, F02 and F05 has been explicitly checked rather than assumed.

Interactive practice

• Type A A gradual change over a year Recognition / application · Foundation
• Type B Smooth decline, or one step at a time? Boundary / differential · Boundary
• Type E Just getting older? Misconception correction · Foundation

Retrieval prompts

Try answering each of these from memory before revealing where to check. Nothing you think or type here is sent or saved anywhere.

1. Without looking back at the page, state the one feature of consciousness that most reliably separates F00 from F05.

   Reveal answer location

   Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.

   I recalled this I need to review this

2. Name one feature that would make you seriously consider F01 instead of F00.

   Reveal answer location

   Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.

   I recalled this I need to review this

3. Explain in one sentence why memory loss alone is not, by itself, enough to classify a case as F00.

   Reveal answer location

   Check Duration and course, Diagnostic boundary, or the rapid revision card below — the cue you need is one of those, in this category's own already-authored wording.

   I recalled this I need to review this

These self-checks are a personal study aid only, visible to you on this page for this visit — they are not stored and do not affect your mastery dimensions.

Related glossary terms

• Dementia

  A syndrome, usually of chronic or progressive course, in which there is decline in memory and at least one other cognitive domain (such as language, planning or judgement) severe enough to impair everyday functioning, occurring with clear consciousness. Dementia is a syndrome that can arise from several different underlying diseases, not a single diagnosis.

  Open full glossary entry →

• Delirium

  An acute, transient disturbance of consciousness and attention, with a fluctuating course over hours to days, usually caused by an underlying physical illness, intoxication, or medication effect. Delirium is distinguished from dementia mainly by its acute onset and fluctuation, not by confusion alone.

  Open full glossary entry →

• Cognitive domain

  A distinct area of mental functioning that can be separately assessed, such as memory, language, attention, planning/executive function, or visuospatial ability. Classifying organic mental disorders often depends on which domain(s) are affected and whether the pattern is isolated or multi-domain.

  Open full glossary entry →

• Insight (clinical)

  The degree to which a person recognises that their experiences (such as unusual beliefs or perceptions) may reflect an illness rather than external reality. Insight can vary and is not itself a classification criterion, but is often noted educationally.

  Open full glossary entry →

• Confabulation

  The unintentional production of fabricated or distorted memories, without the intent to deceive, sometimes seen alongside significant memory impairment. Confabulation is a possible accompanying feature, not itself a required or defining criterion of any single category.

  Open full glossary entry →