What is delirium?
Delirium is an acute disturbance of brain function. It primarily affects attention, consciousness, and cognitive function. Unlike dementia, delirium does not develop over months or years, but rather within hours to a few days. It typically follows a fluctuating course: the patient may be relatively lucid in the morning and completely disoriented by evening.
The key difference from other forms of confusion:
- Acute onset: Symptoms begin suddenly, often following surgery, an infection, or a change in medication.
- Fluctuating course: Confusion varies throughout the day—often worsening in the evening and at night.
- Generally reversible: With timely treatment, delirium resolves completely in most cases.
Not all cases of delirium present the same way. Doctors distinguish three forms that differ fundamentally in their presentation:
Hyperactive delirium is the form most people are familiar with: The patient is restless, agitated, tries to get up, pulls on tubes and cables, and may experience hallucinations. This form is quickly recognized—it is conspicuous and requires immediate action.
Hypoactive delirium is the exact opposite—and at the same time the more dangerous form, because it is so easily overlooked. The patient appears sleepy, withdrawn, barely responds when spoken to, and shows little initiative. On the ward, this behavior is often dismissed as “tired after surgery” or “age-related.” In fact, hypoactive delirium is the most common form and goes unrecognized in up to 70 percent of cases.
The mixed form alternates between phases of restlessness and phases of drowsiness. It is the most difficult variant to diagnose because the clinical picture is constantly changing.
???? Remember: If an older person in the hospital suddenly becomes unusually quiet and apathetic, this is not “normal” behavior. Actively ask for a delirium screening.
Delirium in older adults is one of the most common acute complications among older people in the hospital. The figures are striking:
- General hospital admissions: About 20 to 30 percent of all patients over the age of 65 develop delirium during their stay.
- After surgical procedures: Up to 50 percent of older patients are affected after major surgeries—especially after hip and knee surgeries.
- In intensive care units: Here, the delirium rate is 60 to 80 percent.
- Undiagnosed cases: An estimated 30 to 40 percent of all cases of delirium go undiagnosed in everyday clinical practice—the hypoactive form, in particular, often goes undetected.
These figures show that delirium is not a rare occurrence, but rather one of the central challenges in the care of older patients. And this is precisely where geriatrics comes in: We actively screen for delirium because we know how common it is—and how serious the consequences can be if it is overlooked.
Causes and Risk Factors
Delirium is almost never caused by a single factor. It is the result of a combination of factors: on the one hand, there are factors that make the patient susceptible; on the other hand, there are acute triggers that push the patient over the edge.
As a geriatrician, I think of this in terms of a risk management model: The more pre-existing conditions (predisposing factors) a patient has, the less acute stress (triggering factors) is needed to trigger delirium.
- Age over 70
- Pre-existing dementia or cognitive impairment (the strongest single risk factor)
- Impaired vision or hearing
- Polypharmacy—taking five or more medications at the same time
- Malnutrition and dehydration
- Limited mobility and frailty
- Previous episodes of delirium
- Surgery — particularly hip and knee replacements and cardiac surgery — postoperative delirium is one of the most common complications
- Infections — urinary tract infections and pneumonia are the most common triggers
- Medications — particularly benzodiazepines (sleeping pills and sedatives), anticholinergics, and opioids
- Pain — both untreated and overtreated pain
- Metabolic disturbances—electrolyte imbalances, blood sugar fluctuations, and renal dysfunction
- Urinary catheters, restraints, unfamiliar surroundings
→ For more information on medications that contribute to delirium, see our article on polypharmacy in older adults.
???? Practical tip for family members: Bring a current list of medications with you to the hospital. Ask the care team if any of the medications are on the PRISCUS list—a list of drugs considered potentially unsuitable for older adults. Targeted deprescribing of unnecessary medications can make a world of difference here.
Recognizing Symptoms — A Checklist for Family Members
Delirium can manifest in many different ways. As a family member, you can watch for the following warning signs. Distinguishing between depression and dementia is often crucial:
- Sudden confusion: The patient does not know where they are, what day it is, or why they are in the hospital.
- Attention problems: They cannot follow a conversation, wander off topic, or lose their train of thought.
- Day-night reversal: Sleepy during the day, awake and restless at night.
- Hallucinations: The patient sees things that aren’t there or talks to people who aren’t present.
- Unusual drowsiness: The patient is difficult to wake or reacts noticeably slowly—the often-overlooked hypoactive delirium.
- Fidgeting and restlessness: Pulling on cables, tubes, or the bedspread.
- Personality changes: The patient behaves completely differently than usual—aggressively, anxiously, or apathetically.
The most important rule of thumb: Any sudden change in the behavior of an older adult in the hospital should be considered a possible case of delirium until proven otherwise.
Diagnosis: How is delirium diagnosed?
The diagnosis of delirium is primarily clinical—that is, the physician identifies it through targeted observation and questioning. Standardized screening tools are now available for this purpose, enabling a reliable assessment within a few minutes. In geriatrics, a comprehensive geriatric assessment is also essential:
- Confusion Assessment Method (CAM): The most extensively studied tool internationally. It assesses four characteristics: acute onset, impaired attention, impaired consciousness, and disorganized thinking. A 2023 meta-analysis of 38 studies involving 7,378 patients showed a sensitivity of 80 percent and a specificity of 98 percent—meaning that if the CAM indicates delirium, it is highly likely to be present.
- 4AT Test: A rapid screening tool that can be administered in under two minutes without special training. It assesses alertness, orientation, attention, and whether an acute change is present.
- Nursing Delirium Screening Scale (Nu-DESC): A nursing screening tool that can be used routinely in everyday ward care—ideal for ongoing monitoring.
In addition to identifying delirium, the treatment team specifically investigates the underlying cause: blood tests (infection markers, kidney function, electrolytes), urinalysis, medication review, and, if necessary, imaging studies. It is also important to determine whether the acute confusion is caused by an undiagnosed mild cognitive impairment (MCI) or early-stage Alzheimer’s disease.
→ To learn how doctors systematically assess the overall health status of older adults, read our article on geriatric assessment.
Treatment: What Helps with Delirium?
The treatment of delirium follows a clear three-step approach—and this is precisely the approach we take in geriatrics for any acute deterioration:
The most important step is identifying and treating the trigger. A urinary tract infection is treated with antibiotics, an electrolyte imbalance is corrected, and a medication known to cause delirium is discontinued or switched. Without addressing the underlying cause, delirium cannot resolve. In patients who have experienced a fall or following a femoral neck fracture, the risk of delirium is particularly high and must be taken into account from the very beginning.
In parallel with treating the underlying cause, non-pharmacological measures help alleviate symptoms and promote orientation:
- Familiar caregivers at the bedside—familiar faces are reassuring.
- Orientation aids: a clock, calendar, personal items, and photos.
- Glasses and hearing aids—sensory impairments can increase confusion.
- Actively maintain a day-night rhythm: light and activity during the day, rest and darkness at night.
- Early mobilization—even briefly sitting up on the edge of the bed can help. This is precisely where early geriatric rehabilitation comes in.
- Ensure adequate fluid and food intake.
Medications to treat delirium symptoms (e.g., low-dose haloperidol or risperidone) are used only if the patient poses a danger to themselves or others. They do not treat the underlying cause but rather alleviate symptoms—and can themselves cause side effects. In geriatrics, we therefore use medications as sparingly as possible.
???? Tip for family members: You can actively contribute to the treatment. Speak calmly and clearly with the patient. Explain where they are and why. Bring familiar objects with you. Your presence is one of the most effective “therapies” for delirium.
Can delirium be prevented?
Yes—and this is precisely where one of geriatrics’ greatest areas of influence lies. Studies show that up to 40 percent of all cases of delirium can be prevented through targeted preventive measures. The most effective measures are non-pharmacological. Our article on delirium prevention in the hospital provides a detailed overview:
- Provide orientation: Regular interaction, a clock and calendar in the room, and consistent caregivers.
- Protect sleep: Reduce nightly routine checks (blood pressure, temperature). Minimize noise and light at night.
- Encourage early mobility: Every day spent in bed depletes muscle strength and orientation—and contributes to sarcopenia and immobility in older adults. Simply sitting up on the edge of the bed on the first day after surgery reduces the risk of delirium.
- Ensure adequate fluid intake: Dehydration is one of the most common preventable triggers.
- Review medications: Before every admission and after every surgery: Are patients taking medications that increase the risk of delirium? Are there alternatives?
- Address sensory impairments: Glasses and hearing aids belong by the bed, not in the nightstand.
Long-term consequences: Why delirium must be taken seriously
Delirium is more than a temporary episode. Research increasingly shows that delirium can have long-term consequences—including an increased risk of developing Alzheimer’s disease or other forms of dementia:
- Increased mortality: Patients with delirium have twice the mortality rate in the following months compared to others.
- Increased risk of dementia: Delirium doubles the risk of developing dementia in the following years—even in patients who previously had no cognitive impairments.
- Longer hospital stay: An average of 5 to 10 additional days in the hospital.
- Loss of function: Many patients do not return to their previous level of functioning after experiencing delirium. Frailty syndrome, in particular, can worsen significantly as a result.
- Higher rate of nursing home admissions.
At the same time, it is important to note that delirium is generally reversible. In most patients, the acute confusion resolves completely within a few days to a few weeks—provided that the underlying cause is treated and recovery is supported by geriatric care.
When should you consult a geriatrician?
If an older person in the hospital suddenly becomes confused—suggesting a possible case of delirium—I recommend that family members take the following steps:
- Actively speak with the nursing staff: “My mother has been confused since yesterday. Has a delirium screening been performed?”
- Ask for a geriatric evaluation: “Can a geriatrician be consulted to assess the risk of delirium?” A standardized frailty screening is part of modern geriatric diagnostics.
- Bring relevant information with you: a current list of medications, pre-existing conditions, and whether delirium has occurred in the past.
A geriatrician does not view delirium in isolation but as part of the overall picture: What pre-existing conditions are present? Which medications might play a role? What was the patient’s functional status prior to admission? What risks exist for the future? It is this holistic perspective that makes the decisive difference in the treatment of delirium.
→ Learn more about how such a holistic assessment works in our article on geriatric assessment.
→ Sometimes, confusion is caused by more than just delirium. Read about how doctors distinguish between delirium, dementia, and depression.
