Delirium and its Interrelationship with Dementia

As a mental health practitioner working with people over the age of 65,  I’ve come across people who’ve been discharged from general hospitals with a newly diagnosed dementia who make a full recovery recover soon after discharge.  This might seem slightly odd given that dementia is a degenerative disease.   Miracle working is not at play here.  What has happened is a wrong diagnosis has been made.  In most of these instances a person was suffering from a delirium.
What is Delirium?
Delirium, or acute confusional state,  is a common and  serious illness that can cause changes to a person’s  level of consciousness,  ability to communicate,  behaviour and cognitive function.    These symptoms may be quite marked and distressing and include hallucinations, paranoia, agitation and aggression.   At the other extreme a person might be  sluggish and excessively drowsily.   Many of the symptoms are seen in people with dementia but there are differences in the ways that these illnesses present.  For example:
  • Delirium has a sudden onset, within hours or a matter of days, whereas with dementia deterioration is seen over a much longer time frame.
  • A person with delirium may experience fluctuation in mental state with significant variation in lucid and confused states that would be unusual in a person with dementia.
  • Confusion in a younger person is much more likely to be caused by delirium rather than dementia.
  • A person with dementia is generally alert in spite of their cognitive difficulties.  Delirium has a much greater impact on the ability to stay focused and concentrate.

During assessment it is helpful for healthcare professionals to take a history from friends and family about the onset and nature of symptoms  to differentiate between diagnoses.  Family or friends may wish to challenge a diagnosis of dementia especially if  there has been a sudden onset of symptoms.  This is important as unlike dementia, delirium is often reversible if treatment is timely.

What Causes Delirium?

Awareness of potential causes of dementia may help with its prevention and be instrumental in planning appropriate treatment.   A number of factors may be responsible  and inter-related.  These include:
  • Drug therapy:  Many types of medication, commonly prescribed and available over the counter, including those for mental health problems, insomnia, heart conditions,  pain relief and urinary conditions have the potential to cause delirium.   Be particularly suspicious of drugs which have been newly prescribed as being the potential cause.   Anaesthetics used during operative procedures can also be a cause.
  • Infection:     Urinary or respiratory tract infections, infected wounds and systemic bacterial or viral infections are all common causes of delirium.
  • Drug and alcohol abuse or withdrawal
  • Dehydration
  • Physiological imbalance: Delirium can be indicative of abnormal blood composition or hormonal imbalance.
  • Inability to eliminate waste products from body:  Urinary retention and faecal impaction have the potential of causing delirium alongside other medical complications.
Delirium and dementia
As I have already highlighted it can sometimes be difficult for health professionals to differentiate between dementia and delirium.  However these two conditions  are not mutually exclusive.  In fact people with dementia have an increased risk of developing a delirium.  As symptoms can be similar it might be more difficult to diagnose a delirium that superimposes dementia.
People who support those with dementia should be mindful that changes in a person’s level of function, personality or alertness may not be attributable to dementia, particularly if these have a rapid onset.  Do not hesitate in having a medical review, however insignificant these changes seem. Rapid treatment of delirium gives a greater chance of effective treatment.  However after recovery from delirium be aware that a person with dementia might not regain the ability to function at the same level as before they became unwell.


Treatment will include addressing the medical causes of the delirium which might be multi-factorial.  However it will also include provision of extra care and support.  For example a person may require more assistance than usual to maintain activities of daily living.  They might have reduced insight and be more prone to safety lapses.  In particular their falls risk may increase.    Short term use of medication or non pharmacological approaches might  be needed to manage agitation and distress.  More intensive care support and environmental adaptations may be required in a care home, hospital setting or the home environment to meet these temporary needs.  As care needs may be different from the norm for the individual concerned specialist advice and support may be needed at these times.

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