About delirium and its assessment
Delirium is one of the most common and most serious acute conditions in hospital — and one of the most frequently missed. Understanding what it is, and how assessment tools differ, is the first step to detecting it reliably.
Urgent medical assessment
Sudden new confusion, drowsiness or altered behaviour needs urgent medical assessment. This website cannot diagnose delirium or advise on an individual patient.
What delirium is
Delirium is an acute, usually fluctuating disturbance of attention and awareness, accompanied by additional changes in cognition, that develops over hours to days and is caused by an underlying medical problem — infection, medication, surgery, metabolic disturbance, and many others. Its hallmark is inattention, and its course typically fluctuates through the day.
Motor activity may be hyperactive (agitated, restless), hypoactive (drowsy, withdrawn, quiet) or mixed; some patients do not fit a motor subtype. Hypoactive presentations are common and particularly easy to miss.
Why detection matters
Frequency varies markedly by population and method: delirium affects about 20–30% of people on medical wards, around 15% of older adults assessed in emergency departments, and is especially common in critical care and mechanical ventilation. It is associated with longer stays, mortality, loss of independence and later cognitive decline. Recognition allows urgent assessment and treatment of underlying causes, but screening alone has not been shown to prevent all associated harm.
The recognition gap
Without a structured tool, clinicians miss a large proportion of delirium — especially the hypoactive form. Brief, validated assessment tools exist precisely to close that gap, and their routine use is recommended in national and international guidelines.
How the tools differ
The instruments in this directory are not interchangeable. They were built for different jobs:
Seconds to a couple of minutes. Case-finding at scale — flag who needs a fuller look (e.g. 4AT, DTS, UB-2).
Structured assessment supporting identification of delirium against defined criteria (e.g. CAM, 3D-CAM, bCAM).
Quantify how severe delirium is and track change over time (e.g. MDAS, DRS-R-98, CAM-S).
Designed for repeated use to catch onset or resolution across a shift (e.g. Nu-DESC, DOS, RADAR).
Draw on family or carer observation, valuable when baseline cognition is uncertain (e.g. SQiD, FAM-CAM).
Adapted for contexts such as intensive care or paediatrics, where standard tools do not fit (e.g. CAM-ICU, CAPD).
What makes a good bedside tool
- Brief and feasible in the time clinicians actually have.
- Minimal training — or clearly specified training — so results are consistent between staff.
- Assesses attention, acute change or fluctuation, and relevant changes in arousal without assuming that arousal is always abnormal.
- Validated in your setting and population against a proper reference standard.
- Usable in drowsy or uncooperative patients, not only in those who can fully engage.
Selected source, verified against PubMed: emergency-department prevalence — Chen F, et al. Prevalence of delirium in older adults in the ED: systematic review and meta-analysis (pooled 15.2%). Am J Emerg Med 2022. PubMed. General-ward and ICU ranges are widely reported figures from the delirium literature and vary by population and method. This page is medical information, not individual clinical advice.