🧭 When to suspect

Dementia is an acquired, progressive decline in cognition – affecting memory, reasoning, language, visuospatial skills, executive function or personality – that is severe enough to impair everyday function and is caused by disease of the brain. The hallmark of the commonest type, Alzheimer's disease, is an insidious, gradual decline with early loss of memory for recent events. The two great mimics to exclude are delirium (acute onset, fluctuating course, impaired attention and consciousness) and depression (“pseudodementia”).

The key skill in primary care is to recognise the pattern, exclude reversible causes, and refer to a specialist memory service for diagnosis. A confident subtype diagnosis is a specialist task – but recognising the typical pattern shapes the urgency and the route of referral.

Subtype	Pattern and pointers
Alzheimer's disease	Commonest cause. Insidious, gradual decline; early episodic memory loss, word-finding and executive difficulty.
Vascular dementia	Often stepwise deterioration; vascular risk factors, prior stroke/TIA, focal neurological signs.
Mixed dementia	Coexisting Alzheimer's and vascular pathology – very common in older people.
Dementia with Lewy bodies	Fluctuating cognition, visual hallucinations, spontaneous parkinsonism, REM sleep behaviour disorder. Antipsychotic sensitivity – a key safety issue.
Frontotemporal dementia	Often younger onset (< 65); early personality / behaviour change or language decline, with memory relatively preserved early.

Suspect dementia in an older adult with persistent, progressive cognitive or functional decline, particularly with a corroborating collateral history. Raise the index of suspicion with vascular risk factors, a family history, Parkinsonian features, or a high anticholinergic medication burden.

Source: NICE NG97

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