Delirium or dementia

What features might Mr. Williams have that are more suggestive of delirium as opposed to dementia?

Delirium or Dementia: Knowing how to tell the difference

Delirium and dementia are both frequently found in older hospitalised patients. Although some symptoms and characteristics of each may appear similar different diagnostic mechanisms are responsible for the changes in behaviour seen(37). Additionally the risk factors and outcomes differ for each syndrome(36). However, both dementia and delirium have extreme consequences for the patient and their family (38) and complicating the situation further is the fact that both can evolve concurrently or coexist making differential diagnoses difficult(38-40).

Delirium is a syndrome characterised by a change in consciousness and cognition which develops over a short period of time, usually hours to days(21). It has a tendency to fluctuate during the course of the day with symptoms appearing worse at night(18). Patients affected by delirium have a reduced awareness of the environment around them and have a decreased ability to focus, sustain or shift attention(3,41).

In contrast, dementia is a syndrome of progressive, usually gradual cognitive decline(36). It is characterised by multiple cognitive deficits that include impairment in memory, emergence of behavioural disturbances, and interference with daily function and independence, which tend to persist in an unchanged form for longer than a few months(3).

As older patients with dementia enter an acute care setting the stress of illness, change of environment and their associated pre-existing decrease in cognition increases their risk of developing delirium(42,43). Cognitive decline is claimed to be the main risk factor for delirium(44). However, this delirium is often under-reported as it often goes unrecognised or is inaccurately classified as worsening dementia(43).

If a person with dementia or underlying cognitive impairment suddenly develops a change in their baseline cognitive status delirium should be suspected and a full delirium screen (CAM) undertaken. Delirium and dementia are reportedly seen together in approximately 30%-60% of older general hospital patients(45). It is important that if delirium is identified then the cause needs to be found and management and treatment strategies implemented. Delirium is reversible even in patients with underlying dementia.

Click below to download a table which provides some criteria for differentiating dementia and delirium.

Delirium & Dementia differentiating features (PDF file, 113KB)

Delirium superimposed on dementia (DSD) is the name given to delirium which develops in a person with pre-existing dementia. Given that dementia is one of the strongest risk factors for delirium(1) DSD would obviously be a relatively common occurrence in older hospitalised persons. A recent article suggests that factors which lead to the development of DSD can lead to a temporary loss of cognitive reserve in these people. Therefore they suggest that cognitive stimulation, specifically tailored recreational activities, have the potential to improve/spare remaining cognitive reserve resulting in improved outcomes.

For further information about delirium superimposed on dementia see "Delirium superimposed on dementia: An algorithm for detecting and managing this under-recognized confluence of conditions " continuing education article by Dr. Donna Fick and Dr. Lorraine Mion.