The Difference Between Delirium and Dementia

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.

Diagnosing Alzheimer’s Disease

Unlike cancer or heart disease, there isn’t a single diagnostic test for Alzheimer’s. Doctors have a toolbox of approaches and questions that support their eventual diagnoses. Everything they ask and test ultimately provides vital information, so it’s good to be prepared to provide physicians with the knowledge they need. 

Medical workup and history

The doctor will typically begin by asking about the patient’s medical history (specifically changes in cognitive functions and behavior), psychiatric history, and any record of dementia in other family members. The doctor will want to know what symptoms you’ve noticed, when they began, and how often they occur. They’ll also perform a basic physical exam that includes blood pressure, urine/blood samples, listening to the heart and lungs, etc. The doctor will ask about diet, exercise, and alcohol use, as well as medications, so be sure to bring a list.

Neurological exam

After gathering information about medical history, symptoms, and physical health, the doctor will move on to a neurological exam. The bulk of the neurological exam is fairly straightforward, covering reflexes, muscle tone, eye movement, speech, and a few other tests that may indicate brain disorders caused by stroke, tumors, brain fluid, and other issues.

If doctors need to go deeper, they may recommend brain imaging to rule out other causes with symptoms that overlap with dementia, or a PET scan to check for amyloid protein build-up, which is a marker of Alzheimer’s.

Cognitive tests

Cognitive tests evaluate memory, problem-solving skills, language, and attention, and can range in complexity. They’ll determine if the person being tested is aware of their symptoms and the date/time/place, and will test if the person can follow instructions, perform simple math problems, and remember a short list of words in a specific sequence. Other tests in this category screen for depression and mood disorders.

The reason for all of these tests and screenings is to pinpoint the cause of the issues. Symptoms of dementia can often be triggered by something other than Alzheimer’s such as depression, medications, thyroid issues, vitamin B-12 deficiency, or excessive alcohol consumption. The good news: those conditions can be reversed. 

If the diagnosis does point to Alzheimer’s, the news is not as good. But while Alzheimer’s can’t be cured, it can be slowed and planned for with an early diagnosis. The bottom line: If you’re concerned about yourself or a loved one, talk to your doctor.