Delirium is an acute medical problem often resulting in changes in cognitive function and mentation (e.g., the way the brain thinks, remembers, processes information, etc). It can create problems in thinking and cause confusion.
For example: An older adult who typically knows where they live and the day of the week may suddenly NOT know! Or, a person with dementia who is usually agreeable to receiving assistance from caregivers like with taking medications or bathing, may suddenly refuse care, and may even become agitated.
Delirium usually comes on very quickly. Like within hours or a few days.

Sometimes it can be hard to tell the difference between dementia and delirium because so many of the symptoms overlap.
One of the distinguishing characteristics of delirium is that the onset of symptoms is sudden and is very different from how the person with dementia typically is.
Dementia, on the other hand, is a chronic degenerative illness, meaning that the decline in cognitive function and ability typically happens slowly over time.
Because symptoms of delirium and dementia can be similar, so much so that even doctors don’t even get it right, it’s essential that you help your aging parents communicate with their doctors by sharing what your loved one is like at baseline (what they typically look like with dementia) and how the current symptoms you are noticing are different. This will give the doctor clues about the need to evaluate for delirium. Your participation is essential in helping doctors to make an accurate diagnosis.
There are many signs and symptoms of delirium and to complicate matters, they can change throughout the day (palm to forehead). For example, there may be times, like mid-morning where your loved one seems typical and then in the evening, symptoms worsen. Symptoms tend to be worse during the evening and nighttime when it’s dark and things look less familiar.
And, here’s where things get even more complicated! Say your loved one at baseline experiences “sundowning” and then they have a delirium on top of it and their sundowning seems worse. In this case, it can be really hard to tell if it’s sundowning or if there is a medical change- like delirium, leaving you in a real bind!
Here’s where knowing your loved one’s typical presentation with dementia AND knowing the signs and symptoms of delirium are really important (the information below is an excerpt from the Mayo Clinic website description of Delirium*- it’s really good so here you go)
Reduced awareness of the environment
This may result in:
Poor thinking skills (cognitive impairment)
This may appear as:
Behavior changes
These may include:
Emotional disturbances
These may appear as:
It is quite possible for a person to have more than one cause for delirium.
For example: I commonly see older adults with both dehydration and urinary tract infections (UTIs). And this makes sense! If we’re dehydrated, we’re more likely to develop a urinary tract infection. Then, add on new medications, and the person might have dehydration, a UTI and a medication that they are not tolerating well, or that’s interacting with another medication.
In some cases, your loved one may even be hospitalized, being treated for a delirium, but doctors may struggle to pinpoint a cause.
Here’s an overview* of common causes of delirium:
Delirium is more common in older adults! And here’s why! Simply put, older adults are at risk of delirium due to a decreased cognitive reserve, meaning the brain has less ability to compensate to physiological changes as we get older. But, not only does the brain have less reserve as we age, the same is true for our organs. So, when there are changes to an older adult’s physiology (like dehydration, a virus, or an infection), the older body is very sensitive to these changes and becomes more vulnerable to delirium.
This is why if you’re caring for an older adult, you should be aware of some of the signs and symptoms, as well as some of the common causes, so that you know how to prevent a delirium from happening in the first place. Helping your loved one to stay well-nourished, for example, is a great prevention strategy! (Easier said than done- am I right?)
Delirium is also more common under the following situations that disproportionately affect older adults:<
Having dementia actually puts folks at greater risk of developing delirium. And this makes sense! Dementia is a medical condition in the brain. The brain is already compromised, so when there is another issue in the body (like pain or metabolic imbalances) the brain will have a harder time coping and will be more vulnerable to a delirium. Plus, people with dementia may have difficulty communicating when they are in pain or experiencing discomfort, even stating when they are thirsty or hungry, and as a result, a problem may start without any warning.
Delirium is hard on the brain and can create lasting changes in older adults AND people with dementia, so prevention is key! Here are some tips for preventing delirium:
Delirium is a medical emergency and it is critical that you get your loved one medically evaluated and treated! Early diagnosis and treatment of delirium is essential! Here’s why!
Want to learn more about delirium and dementia? The Alzheimer’s Association has a fact sheet here: https://www.alzheimers.org.uk/get-support/daily-living/delirium
References used in this article:
*Mayo clinic: https://www.mayoclinic.org/diseases-conditions/delirium/symptoms-causes/syc-20371386
https://www.bcmj.org/articles/delirium-older-adults-diagnosis-prevention-and-treatment
Dr. Regina Koepp is a board certified clinical psychologist, clinical geropsychologist, and founder and CEO of the Center for Mental Health & Aging: the “go to” place for mental health and aging. Dr. Koepp is a sought after speaker on the topics of mental health and aging, caregiving, ageism, resilience, intimacy in the context of life altering Illness, and dementia and sexual expression. Dr. Koepp is on a mission to ensure mental health and belonging for older adults, because every person at every age is worthy of healing, transformation, and love. Learn more about Dr. Regina Koepp here.
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