AD (Alzheimer's disease)

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Alzheimer's disease is a progressive degenerative disease of the brain causing 50% of the dementia seen in western society. Its cause is unknown.

It may be defined as a clinicopathological entity where there are histological changes of neurofibrillary tangles and senile plaques in a patient with dementia.

An informative history is therefore very important.

  • Alzheimer's disease is usually insidious in onset and develops slowly but steadily over a period of several years
    • affects predominantly the elderly
    • progression is characterised by deterioration in cognition (thinking, conceiving, reasoning) and functional ability (activities of daily living) and a disturbance in behaviour and mood
    • evidence suggests that Alzheimer's disease progression is dependent on age, and the time from diagnosis to death is about 5-20 years (median 5 years in people aged 75-80 years)
    • people with Alzheimer's disease lose the ability to carry out routine daily activities like dressing, toileting, travelling and handling money and, as a result, many of them require a high level of care
    • non-cognitive symptoms in dementia include agitation, behavioural disturbances (for example, wandering or aggression), depression, delusions and hallucinations.

Mental State Examination (MMSE - 30 points) can be used to classify the severity of cognitive impairment in Alzheimer's disease

  • mild Alzheimer's disease: MMSE 21 to 26
  • moderate Alzheimer's disease: MMSE 10 to 20
  • moderately severe Alzheimer's disease: MMSE 10 to 14
  • severe Alzheimer's disease: MMSE less than 10

The diagnosis requires confirmation at post-mortem, although in practise it is made on clinical grounds.


  1. NICE (September 2007).Donepezil, galantamine, rivastigmine (review) and memantine for the treatment of Alzheimer's disease (amended).
  2. Rossor M .Alzheimer's disease. BMJ 1993;6907(307): 779-82.
  3. Sherrington, R et al.. Cloning of a gene bearing missense mutations in early-onset familial Alzheimer's disease. Nature 1995;375: 754-760.
  4. Selkoe, DJ. News & Views. Nature 1995; 375;734-735.

Last reviewed 05/2021