Alzheimer's disease

Last edited 05/2022

Alzheimer's disease (AD) is a progressive degenerative disease of the brain and is considered the most common cause of dementia (1).

It may be defined as a clinicopathological entity where there are histological changes of neurofibrillary tangles and senile plaques in a patient with dementia (1).

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 (2):

  • 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.