About Dementia

The Difference Between Delirium and Dementia

October 19, 2023  •  4 min read

It’s a common experience: an older person suddenly becomes ill and is checked in to the hospital. Just as suddenly, they seem confused, aggressive, or unusually sleepy. Could it be the onset of dementia? Or is it delirium?

Neither diagnosis is one you want to hear. However, if your loved one is diagnosed with delirium, their lucidity and health will often return to normal within a few weeks. Dementia, on the other hand, is a progressive decline that will require ongoing care. It’s important to understand the difference.

What is Delirium?

Delirium is a sudden change in a person’s mental state. It occurs quickly, over the course of a day or two. While delirium can result from intoxication or sleep deprivation, in older people it’s more likely to be connected to other factors. Dementia is the biggest underlying risk factor for delirium. However, in seniors without dementia, other causes like stroke, surgery, medications, dehydration, infection, or disease that causes inflammation (like pneumonia) can all lead to delirium.

Medical professionals break delirium into three categories. Hyperactive delirium may include restlessness, agitation, aggression toward care, hallucinations, delusions, and being unusually vigilant. Conversely, hypoactive delirium often swings in the opposite direction, showing up as lethargy, drowsiness, distraction, disorientation, or withdrawal. Mixed delirium is just as it sounds: a mixture of hyperactive and hypoactive symptoms that can change suddenly and frequently. 

Whatever symptoms your loved one displays, delirium is a serious condition that should be diagnosed and treated immediately.

What is Dementia?

For the layperson, it can be hard to tell the difference between delirium and dementia as the symptoms are so similar. But while delirium is acute (occurring suddenly over the course of a day or two) with symptoms that can morph throughout the day, dementia has a slower onset over the course of months and more consistent symptoms. (Note: one exception is Lewy body dementia, which shares its rapidly shifting symptoms with delirium.)   

Dementia is extremely common—in fact, 50 million people around the world have been diagnosed, a number that grows by 10 million every year. According to the Mayo Clinic, dementia is “a group of symptoms affecting memory, thinking and social abilities severely enough to interfere with your daily life. Dementia is caused by damage to or loss of nerve cells and their connections in the brain. Depending on the area of the brain that’s affected by the damage, dementia can affect people differently and cause different symptoms.”

Just as there are multiple categories of delirium (hyperactive, hypoactive, and mixed), there are different subsets of dementia (Alzheimer’s disease, Vascular dementia, Lewy body dementia, Frontotemporal dementia, and Parkinson’s disease dementia).

As mentioned above, dementia is one of the primary underlying conditions for delirium. But an episode of delirium doesn’t always mean the person also has dementia. So, if your loved one experiences symptoms, stay calm and consult with a doctor. Your input will be helpful in distinguishing what behaviors may be sudden (indicating delirium) and which ones have been slower to start and may be worsening (most likely dementia).

Remember too that if delirium is quickly diagnosed and addressed, recovery time can be short, depending on underlying conditions. And if dementia is diagnosed, there are care options that can help. Your loved one may change significantly, but it is still possible to maintain their joy, dignity, and quality of life.

The behaviors that result from delirium and dementia can cause hardship and distress for families. The more you understand about the conditions, the more you can prepare for the journey ahead. For more information on symptoms, causes, and treatment, visit The Alzheimer’s SocietyThe Mayo Clinic, and this helpful video from Osmosis.