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Delirium Research

Digging Into the Mysteries of Delirium

NIH MedlinePlus recently spoke with Marie A. Bernard, MD, Deputy Director of the National Institute on Aging and a recognized expert on delirium.

Dr. Marie A. Bernard, Deputy Director of the National Institute on Aging and a recognized expert on delirium.

How is delirium distinguished from dementia?

Delirium is an acute change in cognitive function, primarily characterized by confusion and which may wax and wane—whereas dementia is a progressive decline in cognitive function that occurs over months and years.

Does delirium affect older Americans more often than their younger counterparts? Why?

It does. It appears to be that because older adults have more in the way of chronic conditions, hospitalizations, and medications, older adults tend to get delirium more often than younger adults—although younger adults are subject to developing delirium as well.

Some people affected by delirium experience its effects for weeks after the first occurrence. Why is this?

That's part of the mystery of the syndrome. We don't fully understand what's happening in the basic neuroscience of delirium. It's part of what our scientists are interested in figuring out.

Delirium often affects patients in a hospitalization situation, particularly where a patient has been heavily sedated. What is the connection between sedation, hospitalization, and delirium?

Again, we're not totally clear on what the neurological underpinnings of delirium are. There are some basic changes in the neurotransmitters that occur—changes to the serotonin system, changes to the cholinergic system. Neuroinflammation has been proposed as a possible mechanism for vulnerability to delirium. However, we have not yet established if neuroinflammation is a pre-existing state that makes one vulnerable to delirium in the presence of sedative medications and anesthesia, or if neuroinflammation may be a consequence of sedative effects on the aging brain. In the hospital, you get lots of different medications that can interact and affect the brain, and you're also off your normal schedule—frequently awakened, for example, for blood pressure readings and other needs, and that lack of sleep can contribute to delirium. Additionally, when in the hospital, patients are often on multiple medications that can potentially interact or have a direct effect on cognition. Put all those factors together and it puts one at particular risk for developing delirium.

Fast Facts

  • More than 7 million hospitalized Americans suffer from delirium each year.
  • Among hospitalized patients who survived their delirium episode, the rates of persistent delirium at discharge are 45%, 1 month 33%, 3 months 26%, and 6 months 21%.
  • More than 60% of patients with delirium are not recognized by the health care system.

Source: American Delirium Society,

Why is it important that we diagnose delirium and treat it more effectively?

What's been found is that delirium is a very common occurrence—a third or more of older adults in the hospital experience delirium. The challenge is that delirium can be a waxing and waning sort of thing, so that the same patient can be fine one hour and behaving erratically in the next. Whether it's a delirium episode that's difficult to manage or one where the patient is quiet, it's an issue. Delirium is linked to longer hospital stays, complications, and higher mortality.

NIA is supporting research into delirium. What do we hope to learn from this research?

We want to get a much better understanding of its underlying cause. If we can figure that out, then we'll be much more effective in treating it and preventing it. We don't have truly good means of treating it once it's developed. Through our research, we hope to get a better handle on all of those things.

Can hospitalization delirium be prevented? What should we be doing to address the problem of delirium in the hospital setting?

We simply need to be aware that it's a risk, so we need to do a baseline assessment of a patient's cognitive status. We need to try to maintain as normal a schedule as possible—interruptions during the night do not help. We also want to keep people in the hospital as short a time as possible. We need to keep them well hydrated while they're in the hospital, limit interacting medications and particularly sedatives and other centrally acting medications, and we need to make sure that glasses and hearing aids are accessible.

Read More "Delirium Research" Articles

Where Am I? / Digging Into the Mysteries of Delirium / The Impact of Delirium

Fall 2015 Issue: Volume 10 Number 3 Page 15