What’s the Difference Between Delirium and Dementia?


When interning at a nursing home, I encountered a patient who was complaining that her medication was causing hallucinations.  But since that was not a publicized side effect of her medication, the medical staff thought that the hallucinations were caused by dementia or psychosis. Upon performing a deeper dive into the literature from clinical trials on that medication, we found that hallucinations in fact had occurred, although were extremely rare. When the doctor changed her medication, the hallucinations subsided and she returned to her previous level of functioning. The hallucinations turned out to be drug-induced delirium, not symptoms of dementia. 

Symptoms of dementia and delirium overlap significantly, but prognoses are quite different. While dementia is a progressive syndrome (gradually increasing in severity over time), delirium comes on quickly and can often be reversed when treated effectively. Delirium can be triggered by environmental factors such as a stay in the hospital or biological factors such as medication. 

Both delirium and dementia negatively impact attention, awareness, and cognition. Disturbances in the sleep-wake cycles of those with delirium can mirror the sundowning effect seen in patients with Alzheimer’s disease. Additionally, those experiencing delirium or dementia may exhibit behavior that is out of character, such as increased anxiety or agitation. In other words, the behavioral impact of delirium and dementia are very similar, and can be hard to differentiate. 

The difference between delirium and dementia

The primary clue that a patient may be suffering from delirium and not dementia is a rapid onset of symptoms such as disorientation and confusion. While dementia typically comes on slowly, delirium can have an onset of only a few hours or days. Delirium and dementia can co-occur however, so it can often be challenging to interpret whether an increase in symptoms is due to the progression of dementia, or onset of delirium. Additionally, in patients with mild dementia, a bout of delirium can, at times, seem to permanently catapult a patient into a stage of more severe cognitive deficit. For these reasons, an accurate history of the patient’s prior cognitive functioning, temperament, and behaviors as provided by a close family member or friend is extremely important to ensuring proper diagnosis and treatment.

Possible causes of delirium

According to the American Psychiatric Association, up to 60% of older residents of residential care facilities are diagnosed with delirium, as well as up to 87% of people recovering from surgeries in intensive care. Common causes are medical conditions, reactions to medications, sleep disturbances, and environmental changes (particularly for those already experiencing neurocognitive decline).

Medical conditions having minimal effects on the cognitive functioning of younger adults, such as the onset of urinary tract infections, are frequently seen to contribute to delirium among older adults. Therefore, when a patient is experiencing a rapid change in cognitive function, a thorough physical evaluation is extremely important.

Medications can also be the culprit. Medicine is processed differently in the bodies of older adults, which can lead to greater prevalence of side effects and interactions. Drug trials are not often conducted on older patients, so the publicized side effects of a medication may not cover the full range of effects they may have on older people. 

Often, the key to quickly resolving challenges with delirium lies in the advocacy of someone who knows and cares about the patient. Without a strong understanding of a patient’s baseline behaviors, medical staff in residential facilities may make the mistake of attributing symptoms of delirium to dementia, delaying treatment and potentially leading to longer-term decreased levels of cognitive and psychological functioning, which can have severe, or even fatal consequences.

Submit your review

Create your own review

Average rating:  
 0 reviews

Be The First to Add a Tip About This