Delirium vs. Dementia: What’s the Difference?


While delirium and dementia have symptoms in common, it’s important to understand what makes them different. Dementia refers to a group of symptoms that affect cognitive abilities. It usually gets worse over time and has no cure. Delirium can come on within a day or two, and it’s usually easier to tell when these symptoms begin. In many cases, delirium is reversible.

As a caregiver, you know your loved one best. If you spot a sudden change in personality or the onset of a new symptom, ensure they receive prompt medical attention.

What is the difference between delirium and dementia?

Although both conditions affect the brain and cognitive processes, there are three major differences between delirium and dementia.

Seniors with delirium experience:

  • A sudden onset of symptoms within hours or days
  • Symptoms that fluctuate over hours or days
  • An inability to focus

Seniors with dementia experience:

  • A slow onset of symptoms, which may not be clearly noticeable at first
  • Progressive worsening of symptoms over months or years
  • Memory loss

Read: 10 Signs of Alzheimer’s Disease and Other Dementias

Comparing delirium and dementia symptoms

Doctors may overlook delirium, particularly in hospital settings or in seniors who already have dementia. Attentiveness and advocacy are central to your role as a caregiver. If you see things that are outside of your loved one’s typical behaviors, request to speak to their doctor.

You’ll also want to keep in mind that there are different kinds of delirium. Someone with hyperactive delirium will appear more agitated, restless, and vigilant. On the other hand, someone with hypoactive delirium will be unusually drowsy and slow to respond. Sometimes these symptoms are mistaken for depression. According to the Cleveland Clinic, hypoactive delirium makes up 75% of delirium cases.

Sometimes a senior with delirium can experience a combination of hyperactive and hypoactive delirium. They may be alert and confused one moment and then unexpectedly drowsy the next. This is known as mixed delirium.

The following chart shows common delirium and dementia symptoms, as outlined in the journal Innovations in Clinical Neuroscience. Note that if your loved one has Lewy body dementia, they may also experience hallucinations.

Symptoms and featuresDelirium symptomsDementia symptoms
Rate of declineSudden difficulty performing familiar tasksSlow decline in ability to perform familiar tasks
Effect on cognitionConfusion, disorientation, difficulty focusing and paying attentionConfusion, forgetfulness or memory loss, poor decision making or judgment skills
Effect on temperamentAgitation, delusions, paranoia, hallucinations, hypervigilance, unwillingness to accept careAgitation, delusions, paranoia, changes in personality
Effect on languageTrouble following or participating in conversationsTrouble remembering words
Effect on moodSudden and unpredictable mood swingsPredictable changes, such as those seen with sundown syndrome

Causes of dementia

Dementia does not have a single cause, and each senior can experience a variety of symptoms. Seniors with a family history of Alzheimer’s disease may be at a greater risk of experiencing it themselves. The symptoms seniors experience with dementia are due to changes in the brain. This may be due to damage to the brain’s nerve cells, a buildup of plaques, or reduced blood flow to the brain.

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Causes of delirium

While dementia is caused by physical changes in the brain, delirium can have many different causes not related to brain damage. If you think your loved one may be experiencing delirium, here are some questions to ask yourself:

  • Has your loved one’s medication regimen changed recently?
  • Have they had a surgical procedure where they were under general anesthesia?
  • Have they had a recent illness such as the flu or pneumonia?
  • Could they have a urinary tract infection (UTI)?
  • Could they be dehydrated or feeling the effects of malnutrition?
  • Do they have a chronic illness or worsening illness?
  • Are they in pain or under emotional distress?

These are all possible causes of delirium, but this is not an exhaustive list. Visual or hearing impairment, previous episodes of delirium, family history, and cognitive conditions can all predispose a senior to delirium.

It is possible for someone with dementia to experience delirium, however, it may not be as easy to spot the signs. If your loved one has been diagnosed with Alzheimer’s disease or another form of dementia, take extra care to note sudden changes in their symptoms and behavior.

Delirium, dementia, and care: What you can expect

Delirium can usually be reversed. Treatment typically addresses the underlying cause. If the delirium is caused by an infection, for example, the doctor would likely treat with antibiotics.

Seniors may experience delirium while in the hospital, especially after a surgery. As a caregiver, you can offer a familiar presence that others can’t. Speak calmly and quietly to your loved one, reassure them, and provide familiar, comforting objects from home, such as photographs or a cozy blanket.

Depending on the cause, the effects of delirium can be long-lasting. This can be a very stressful experience, and seniors may experience anxiety surrounding those memories long after delirium ends.

Delirium has been linked to dementia in numerous ways. When it comes to delirium versus dementia, the two are actually very much intertwined. Someone with dementia may have a noticeable worsening of symptoms after delirium. Sometimes, a senior will not have a diagnosis of dementia before experiencing delirium, but might receive one shortly afterwards. This is described as the delirium “uncovering” the dementia, as noted by the Alzheimer’s Society.

Read: What to Do If You Suspect Someone Has Dementia

In some instances, a senior with dementia may experience a decline in functional abilities after delirium. They may need additional help with activities of daily living, such as bathing, dressing, or eating. In some cases, changes like this can be permanent.

While you navigate the changes your loved one is going through, you may want to consider an in-home caregiver. They can help with personal care and household tasks, allowing you to spend quality time with your loved one and prioritize your own well-being.

If your loved one has dementia that has gotten worse after delirium, consider exploring memory care. Memory care communities feature specially trained caregivers to help seniors with memory loss, plus activities and therapies designed to foster independence and preserve cognitive abilities.

The information contained in this article is for informational purposes only and is not intended to constitute medical, legal or financial advice or to create a professional relationship between AgingCare and the reader. Always seek the advice of your health care provider, attorney or financial advisor with respect to any particular matter, and do not act or refrain from acting on the basis of anything you have read on this site. Links to third-party websites are only for the convenience of the reader; AgingCare does not endorse the contents of the third-party sites.

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