Evidence for the Diagnostic Criteria of Delirium

An Update

Dan G. Blazer; Adrienne O. van Nieuwenhuizen


Curr Opin Psychiatry. 2012;25(3):239-243. 

In This Article

Delirium and Dementia

The most common differential diagnostic issue when evaluating confusion in older adults involves disentangling symptoms of delirium and dementia. The clinician must determine whether the patient has delirium, a delirium superimposed on a preexisting neurocognitive disorder such as Alzheimer's disease, or a major neurocognitive disorder separate from delirium (such as dementia).[5,11,25] One study found that the frequency of delirium in patients hospitalized with dementia was as high as 89%.[26] In another study, the risk for delirium was three times greater in nursing home patients who had a diagnosis of dementia.[27] This correlation is present in both directions, as patients with a history of delirium have a higher incidence of dementia.[28]

Delirium may increase the pace of cognitive decline in patients with Alzheimer's disease. Fong et al.[29] found that the rate of decline in cognitive scores occurred about three times faster in Alzheimer patients with delirium compared with those who did not experience delirium. This suggests that the pathological processes involved in delirium may cause neuronal damage which in turn triggers or accelerates persistent cognitive changes.[30•,31] In addition, the overall prognosis of patients with dementia is worse if they also experience an episode of delirium than if they do not.[31,32]

Thus, sorting out the symptoms of delirium and dementia/neurocognitive disorder is a complex task. The traditional distinction between delirium and dementia, according to acuteness of onset and temporal course, is particularly difficult in those elderly who develop 'persistent cognitive impairment' following an episode of delirium.[11,33] This is especially true with the onset of a delirium in the presence of a neurocognitive disorder such as early Alzheimer's disease.[5] In such cases, the symptoms of delirium may persist for an extended period and the cessation of delirium may not be easily identified. Memory impairment is common to both, but patients with a neurocognitive disorder alone are usually alert and do not experience the disturbance in attention/awareness that is characteristic of delirium.

To explore the issue of comorbidity, Meagher et al.[34] recruited patients with DSM-IV delirium, dementia, comorbid delirium–dementia, and cognitively intact controls. They were assessed using the DRS-R98[35] and the CTD.[36] Those with delirium only and those with comorbid delirium and dementia had comparable scores on both scales; both groups, as would be expected, experienced greater cognitive impairment than controls. Noncognitive symptoms, such as inattention and disorientation, were more severe in the delirium-alone group compared with the dementia-alone group. Spatial span backwards scores were significantly lower in all patients with any form of cognitive impairment (delirium, dementia, or the comorbid condition) compared with controls, whereas spatial span forwards was significantly diminished in delirium compared with dementia. Therefore, more sophisticated neuropsychological testing may help distinguish delirium from dementia and detect the presence of delirium in a chronically demented patient.

Although the temporal onset and course of cognitive impairments are helpful in distinguishing between delirium and dementia, this remains a challenging task, especially when working with elderly patients. In general, the onset of symptoms in delirium is much more rapid (i.e., usually over hours to days), whereas in a neurocognitive disorder (dementia) the onset is typically more gradual or insidious. Delirium symptom severity characteristically fluctuates during a 24-h period, whereas neurocognitive symptom severity does not. If symptoms of a delirium are clear to the clinician and dominate the clinical picture, information from family members, other caretakers, or medical records may be helpful in determining whether the symptoms of a neurocognitive disorder/dementia were preexisting.


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