Delirium is more common among older people. It is a common reason that family members of older people seek help from a doctor or at a hospital. About 15 to 50% of older people experience delirium at some time during a hospital stay.

Causes

In older people, delirium can result from any condition that causes delirium in younger people. But it can also result from less severe conditions, such as the following:

• Dehydration

• A disorder that normally does not affect thinking, such as a urinary tract infection, influenza, or deficiency of thiamin or vitamin B12

• Pain

• Retention of urine or severe constipation

• Sensory deprivation, as may occur when people are socially isolated or are not wearing their glasses or hearing aid

• Sleep deprivation

• Stress (any type)

• Use of a bladder catheter (a thin tube used to drain urine from the bladder)

Certain age-related changes make older people more susceptible to developing delirium. These changes include

• An increased sensitivity to medications or drugs

• Changes in the brain

• The presence of conditions that increase the risk of delirium

Drugs: Older people are much more sensitive to many medications and drugs. In older people, drugs that affect the way the brain functions, such as sedatives, are the most common cause of delirium. However, drugs that do not normally affect brain function, including many over-the-counter medications (especially antihistamines), can also cause it. Older people are more sensitive to the anticholinergic effects that many of these medications have. One of these effects is confusion.

Age-related changes in the brain: Delirium occurs more often in older people partly because some age-related changes in the brain make them more susceptible. For example, older people tend to have fewer brain cells and lower levels of acetylcholine—a substance that enables brain cells to communicate with each other. Any stress (due to a drug, disorder, or situation) that causes the level of acetylcholine to further decrease can make it harder for the brain to function. Thus, in older people, such stresses are particularly likely to cause delirium.

Other conditions: Older people are also more likely to have other conditions that make them more susceptible to delirium, such as the following:

• Stroke

• Dementia

• Parkinson disease

• Other disorders that cause nerve degeneration

• Use of three or more medications

• Dehydration

• Undernutrition

• Immobility

Delirium is often the first sign of another, sometimes serious disorder. For example, the first symptom in older people with COVID-19 may be delirium, sometimes with no other symptoms of COVID-19.

Symptoms

Delirium tends to last longer in older people.

Confusion, the most obvious symptom, may be harder to recognize in older people. Younger people with delirium may be agitated, but very old people tend to become quiet and withdrawn. In such cases, recognizing delirium is even harder.

Having delirium also increases the risk that older people with COVID-19 will have to stay in an intensive care unit (ICU), go to a rehabilitation facility after being discharged from the hospital, and/or die.

If psychotic behavior develops in older people, it usually indicates delirium or dementia. Psychosis due to a psychiatric disorder rarely begins during old age.

Older people are more likely to have dementia, which makes delirium harder to identify. Both cause confusion. Doctors try to distinguish the two by determining how quickly the confusion developed and what the person’s previous mental function was. Doctors also ask the person a series of questions that test various aspects of thinking (mental status examination). Doctors usually treat people whose mental function suddenly worsens—even if they have dementia—as if they have delirium until proved otherwise. Having dementia increases the risk of developing delirium, and some people have both.

Treatment

Delirium and the hospitalization it usually requires can cause many other problems, such as undernutrition, dehydration, and pressure sores. These problems may have serious consequences in older people. Thus, older people can benefit from treatment managed by an interdisciplinary team, which includes a doctor, physical and occupational therapists, nurses, and social workers.

Prevention

To help prevent delirium in an older person during a hospital stay, family members can ask hospital staff members to help—by doing the following:

• Encouraging the person to move around regularly

• Placing a clock and calendar in the room

• Minimizing the interruptions and noises during the night

• Making sure the person eats and drinks enough

Family members can visit and talk with the person and thus help keep the person oriented. People with delirium may be frightened, and the familiar voice of a family member can have a calming effect.