Delirium

Delirium occurs when the brain receives an external insult powerful enough to disrupt its normal functioning. It can occur at any age, but it is most commonly seen in children and elderly people. In childhood, the brain is vulnerable because it is still developing. In old age, increased vulnerability to delirium is due to factors such as dementia and sensory impairment, which become more common with increasing age. As well as being more vulnerable, elderly people are also more liable to be exposed to the external insults, such as physical illness and medication, that commonly cause delirium. The more vulnerable the individual, the less severe such insults need to be in order to precipitate a delirium. Consequently, the highest rates of delirium are to be found in high-risk populations such as elderly medical, surgical, and psychiatric inpatients. Some elderly patient groups, such as those with hip fractures, appear to be particularly prone to developing delirium. In elderly patients, it is important to distinguish delirium from other mental disorders that occur in old age. This can be difficult, not least because disorders such as dementia and depression are themselves risk factors for delirium, and may be co-morbid with it. A useful rule of thumb is that any sudden worsening of cognitive functioning, particularly if alertness and attention are impaired, should be investigated as delirium until proved otherwise.