Module 6: Exploring Age-Related Body Systems Changes

6.5: Neurological System

6.5.20: Dementia vs Delirium

Dementia is really a syndrome that encompasses any disorder characterized by multiple cognitive deficits that include memory impairment. In the DSMIV (DSM IV, 1994), dementia is categorized according to its presumed etiology. For example: Alzheimer’s type; vascular; other general medical conditions such as HIV, head trauma, Parkinson’s disease; substance induced; or those of indeterminate origin.

An essential feature of a dementia is the development of cognitive deficits that include memory impairment and at least one of the following problems: aphasia, apraxia, agnosia, or a disturbance in executive functioning. These deficits have to cause an impairment in occupational or social functioning and they have to represent a decline from a previously higher level of functioning. Further, different types of dementing processes differentially affect memory—some more severely than others. And while Alzheimer’s type dementia is the most common form, other causes of dementia need to be considered, and reversible causes of dementia excluded (such as hypothyroidism, depression, medications, or a B12 deficiency).

Because treatment options are now increasingly available, it is becoming more important to differentiate between types of dementias. Thus, for example, fronto-temporal lobe dementia more commonly presents with behavioral problems; vascular dementia often presents with a step wise progression; and Lewy body dementia is more commonly associated with Parkinson’s disease. The Alzheimer’s Society website discusses these forms of dementia at Alzheimer’s Society—What is dementia? Visit them if you choose. Dementia.com, a grant supported site, is one which health care professionals may log into for more specific information about dementia. (Note: These links will open in new browser windows which you can close to return here.)

Delirium is an acute alteration in consciousness that can not be explained by a pre-existing or evolving dementia (DSM IV, 1994). It tends to fluctuate over the course of the day and attention span is impaired. Delirium is often accompanied by a disturbance in the sleep-wake cycle and psychomotor behavior. However, it’s very important to realize that the latter can be either increased OR decreased. It’s easy to overlook a quietly delirious older person, but delirium has to be considered a RED FLAG, because it can indicate many underlying pathological processes (such as a UTI, MI, or pneumonia). It also can be superimposed upon an existing dementia; thus any sudden change in cognition in a person with dementia has to be evaluated for an underlying physiological cause (including pain).

The Contrast Table: Differentiating Dementia from Delirium—Key Points

Some clinical characteristics that distinguish dementia from delirium are listed in the attached tables. Delirium usually clears fairly quickly if treated. However, it is increasingly realized that the time course of delirium can be extended, and that it may occur in individuals who have some underlying cognitive impairment which may subsequently become manifest. Thus early treatment and follow-up is important.