I had two discussions this last week about the distinction between delirium and dementia. The first was with a client who underwent major surgery several weeks ago. I have been following this client for several years and several evaluations demonstrating excellent memory. Subsequent to surgery, the client developed a delirium which has cleared. However, for the first time his evaluation scores have dropped. Second, the discussion during Minder’s Keepers at the Alzheimer’s Support Network turned to the same topic.

So let me try to clarify the difference between a delirium and a dementia. By the dictionary a delirium is “an acute mental disturbance characterized by confused thinking and disrupted attention usually accompanied by disordered speech and hallucinations.” By the same dictionary dementia is “usually progressive condition marked by deteriorated cognitive functioning with emotional apathy.”

The critical thing to know is that a delirium has a sudden onset and is reversible in time. A dementia often has a gradual onset and is irreversible. The table below may help with understanding the differences that mark a delirium and a dementia. Be aware that someone with a dementia can also develop a delirium (such as from hospitalization, illness, or medications). In other words this is not an either/or difference.

DELIRIUM DEMENTIA
ONSET sudden or acute often gradual
COURSE rapid changes stable
DURATION hours to weeks months to years
ATTENTION fluctuates normal
HALLUCINATIONS/DELUSIONS often sometimes
MOOD anxious/fearful apathy

Delirium is especially disturbing to caregivers and staff. Delirium is especially likely in those with cognitive impairment or dementia. Delirium adds temporary but substantial burden to all involved. Furthermore, delirium often accelerates decline in those with dementia such as Alzheimer’s disease, Parkinson’s disease, or Lewy Body disease. In a recent study (Annals of Internal Medicine, June 19, 2012) 25% of hospitalized patients with Alzheimer’s disease developed delirium while hospitalized and 79% of those patients were institutionalized, developed further cognitive decline, or died within the next three years.

There are multiple possible causes of delirium. These conditions may confound the diagnosis of dementia and add to the burden and complexity of caregiving.
1. Metabolic disorders such as thyroid disease or diabetes
2. Malnutrition such as vitamin B deficiency
3. Dehydration
4. Neurologic disorders such as stroke
5. Infections such as urinary tract infections
6. Trauma such as head injury, surgery
7. End of life
8. Drug/alcohol use or withdrawal

There are a number of events that may increase the risk of delirium. We need to be especially vigilant in those who are aged, demented, dehydrated, cognitively impaired, on multiple medications, have had a previous delirium, or are severely stressed (e.g., hospitalized). Despite the often profound and frightening symptoms of delirium, it is in itself a temporary condition. It will resolve with treatment of the underlying cause, compassion, and patience.