What is delirium?
Delirium is an acute disturbance of brain function. It primarily affects attention, consciousness and the ability to think. Unlike dementia, delirium does not develop over months or years but within hours to a few days. A fluctuating course is typical: the patient may be relatively clear in the morning and completely disoriented in the evening.
The decisive difference from other forms of confusion:
- Acute onset: The symptoms set in suddenly, often after an operation, an infection or a change of medication.
- Fluctuating course: The confusion varies over the course of the day — frequently worsening in the evening and at night.
- Fundamentally reversible: With timely treatment, delirium resolves completely in most cases.
Not every delirium looks the same. Physicians distinguish three forms that differ fundamentally in their appearance:
Hyperactive delirium is the form most people are familiar with: the patient is restless, agitated, tries to get up, pulls at tubes and cables and may have 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 The patient appears drowsy, withdrawn, barely responds when addressed and shows little initiative. On the ward this behavior is often dismissed as ‘tired after the operation’ or ‘age-related’. In fact, hypoactive delirium is the most common form and is not recognized 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 picture is constantly changing.
???? Remember: when an older person in hospital suddenly becomes unusually quiet and apathetic, this is not ‘normal’ behavior. Actively ask for a delirium screening.
Delirium in old age is one of the most common acute complications in older people in hospital. The figures are striking:
- General hospital admission: About 20 to 30 percent of all patients over 65 develop delirium during their stay.
- After surgical procedures: Up to 50 percent of older patients are affected after major operations — particularly after hip and knee surgery.
- In intensive care units: Here the delirium rate is 60 to 80 percent.
- Unrecognised cases: An estimated 30 to 40 percent of all cases of delirium are not diagnosed in everyday clinical practice — above all the hypoactive form remains undetected.
These figures show that delirium is not a rare event but one of the central challenges in the care of older patients. And this is precisely where the task of geriatrics lies: we actively look for delirium because we know how common it is — and how serious the consequences can be when it is overlooked.
Causes and risk factors
Delirium almost never arises from a single cause. It is the result of an interplay: on one side stand factors that make the patient vulnerable. On the other side stand acute triggers that make the barrel overflow.
As a geriatrician I think in terms of a risk-management model: the more pre-existing burden (predisposing factors) a patient brings with them, the less acute stress (precipitating factors) it takes to trigger a delirium.
- Age over 70 years
- Pre-existing dementia or cognitive impairment (the single strongest risk factor)
- Impaired vision or hearing
- Polypharmacy — taking five or more medications at the same time
- Malnutrition and lack of fluids
- Reduced mobility and frailty
- A previous delirium in the past
- Operations — in particular hip and knee replacement, cardiac surgery — postoperative delirium is one of the most common complications
- Infections — urinary tract infections and pneumonia are the most common triggers
- Medications — above all benzodiazepines (sleeping pills and sedatives), anticholinergics and opioids
- Pain — both untreated and over-treated pain
- Metabolic derangements — electrolyte disturbances, blood sugar fluctuations, kidney function disorders
- Bladder catheters, physical restraints, an unfamiliar environment
→ You will find more on medications that promote delirium in our article on polypharmacy in old age.
???? Practical note for relatives: bring a current list of medications with you to hospital. Ask the treatment team whether any of the medications is on the PRISCUS list — a list of medicines considered potentially unsuitable for older people. Targeted deprescribing of unnecessary medications can be life-changing here.
Recognizing symptoms — a checklist for relatives
Delirium can manifest itself in very different ways. As a relative you can watch out for the following warning signs. Distinguishing it from depression and dementia is often decisive here:
- Sudden confusion: The patient does not know where they are, what day it is or why they are in hospital.
- Attention disorder: They cannot follow a conversation, drift off, lose the thread.
- Day-night reversal: Drowsy during the day, awake and restless at night.
- Hallucinations: The patient sees things that are not there or talks to people who are not present.
- Unusual drowsiness: The patient is barely rousable or responds conspicuously slowly — the often overlooked hypoactive delirium.
- Plucking and restlessness: Pulling at cables, tubes or the bedspread.
- Personality change: The patient behaves completely differently from usual — aggressive, anxious or apathetic.
The most important rule of thumb: every sudden change in the behavior of an older person in hospital should be regarded as a possible delirium until proven otherwise.
Diagnosis: how is delirium identified?
The diagnosis of delirium is made primarily clinically — that is, the doctor recognizes it through targeted observation and questioning. For this, standardized screening instruments are available today that allow a reliable assessment within a few minutes. In geriatrics a comprehensive geriatric assessment is also indispensable:
- Confusion Assessment Method (CAM): The internationally best-studied instrument. It examines four features: acute onset, attention disorder, disturbance of consciousness and disorganised thinking. A meta-analysis from 2023 with 38 studies and 7,378 patients showed a sensitivity of 80 percent and a specificity of 98 percent — meaning: when the CAM indicates a delirium, it is highly likely to be one.
- 4AT test: A rapid screening instrument that can be carried out in under two minutes without special training. It examines alertness, orientation, attention and whether an acute change is present.
- Nursing Delirium Screening Scale (Nu-DESC): A nursing screening instrument that can be used routinely in everyday ward practice — ideal for continuous monitoring.
In addition to detecting the delirium, the treatment team searches specifically for the triggering cause: blood tests (infection parameters, kidney values, electrolytes), urine diagnostics, medication review and, where needed, imaging procedures. Also important is the question of whether a not-yet-diagnosed mild cognitive impairment (MCI) or incipient Alzheimer’s disease lies behind the acute confusion.
→ You can learn how doctors systematically record the overall health situation of older people in our article on the geriatric assessment.
Treatment: what helps with delirium?
The treatment of delirium follows a clear triad — and this is precisely the approach we pursue in geriatrics with every acute deterioration:
The most important step is to identify and treat the trigger. A urinary tract infection is treated with antibiotics, an electrolyte disturbance is corrected, a deliriogenic medication is stopped or changed. Without removing the cause, a delirium cannot resolve. In patients with falls or after a femoral neck fracture, the delirium risk is particularly high and must be taken into account from the outset.
Alongside treating the cause, non-pharmacological measures help to relieve the symptoms and promote orientation:
- Familiar people at the bedside — known faces are reassuring.
- Orientation aids: a clock, calendar, personal objects, photos.
- Glasses and hearing aid — sensory impairments aggravate the confusion.
- Actively shape the day-night rhythm: light and activity during the day, quiet and darkness at night.
- Early mobilization — even a brief sitting up on the edge of the bed can help. Geriatric early rehabilitation starts precisely here.
- Ensure adequate fluids and nutrition.
Medications against the delirium symptoms (e.g. low-dose haloperidol or risperidone) are used only when the patient endangers themselves or others. They do not treat the cause but relieve symptoms — and can themselves cause side effects. In geriatrics we therefore use medications as sparingly as possible.
???? Tip for relatives: you can actively contribute to the treatment. Speak calmly and clearly with the patient. Tell them where they are and why. Bring familiar objects. Your presence is one of the most effective ‘therapies’ for a delirium.
Can delirium be prevented?
Yes — and this is precisely where one of the greatest levers of geriatrics lies. Studies show that up to 40 percent of all cases of delirium can be avoided through targeted preventive measures. The most effective measures are non-pharmacological. Our article on delirium prevention in hospital offers a detailed overview:
- Provide orientation: Regular conversation, a clock and calendar in the room, consistent caregivers in nursing.
- Protect sleep: Reduce nightly routine measures (blood pressure, temperature). Minimize noise and light at night.
- Mobilize early: Every day in bed costs muscle strength and orientation — and promotes sarcopenia as well as immobility in old age. Even sitting up on the edge of the bed on the first day after the operation lowers the delirium risk.
- Ensure fluid intake: Dehydration is one of the most common avoidable triggers.
- Review medications: Before every admission and after every operation: are medications being taken that promote delirium? Are there alternatives?
- Correct sensory impairments: Glasses and hearing aid belong at the bedside, not in the bedside cabinet.
Long-term consequences: why delirium must be taken seriously
Delirium is more than a transient episode. Research increasingly shows that delirium can have long-term consequences — including with regard to the development of Alzheimer’s disease or other forms of dementia:
- Increased mortality: Patients with delirium have twice as high a mortality in the following months by comparison.
- Increased risk of dementia: A delirium doubles the risk of developing dementia in the following years — even in patients who were previously cognitively inconspicuous.
- Longer hospital stay: On average 5 to 10 additional hospital days.
- Loss of function: Many patients do not return to their previous level of function after a delirium. In particular, frailty syndrome can worsen considerably as a result.
- Higher rate of nursing home admissions.
At the same time it holds that: a delirium is fundamentally reversible. In most patients the acute confusion resolves completely within days to a few weeks — provided the cause is treated and the recovery is accompanied geriatrically.
When should you see a geriatrician?
When an older person in hospital is suddenly confused — a suspected delirium in hospital — I recommend the following steps to relatives:
- Actively address the nursing staff: ‘My mother has been confused since yesterday. Was a delirium screening carried out?’
- Ask for a geriatric co-assessment: ‘Can a geriatrician be brought in to assess the delirium risk?’ A standardized frailty screening is part of modern geriatric diagnostics here.
- Bring information with you: a current list of medications, pre-existing conditions, whether a delirium has occurred before.
A geriatrician does not see the delirium in isolation but as part of the overall picture: which pre-existing conditions are present? Which medications may play a role? What was the functional status before admission? Which 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 the geriatric assessment.
→ Sometimes more than just a delirium lies behind the confusion. Read how doctors distinguish delirium, dementia and depression from one another.
