Article Text

Delirium within the emergency care setting, occurrence and detection: a systematic review
  1. Ewan Alexander Barron,
  2. John Holmes
  1. Academic Unit of Psychiatry, St. James University Hospital, University of Leeds, Leeds, Yorkshire, UK
  1. Correspondence to Dr Ewan Alexander Barron, Academic Unit of Psychiatry, Basement floor Beckett Wing, St. James University Hospital, Leeds, Yorkshire LS9 7TF, UK; ewan.barron{at}


Recent recommendations from the Society for Academic Emergency Medicine and the American College of Emergency Physicians identified the detection of delirium in the emergency department (ED) as a ‘high yield’ research objective. This review aimed to determine the occurrence rate, and physician detection rates, of delirium within the ED. A systematic literature review was conducted and identified using online databases. Prospective cohort and cross-sectional studies from hospital EDs were interrogated. Systematic data extraction and assessments of quality were carried out. Searching yielded 723 publications, and 13 papers met inclusion criteria. Occurrence of delirium at admission to the ED ranged from 7% to 20% of patients. Physician diagnosis rates of preconfirmed delirium (using a specified tool) within the ED varied between 11.1% and 46.0%. Many studies used non-validated assessment tools to gather data. Four delirium outcome studies were conducted in the ED setting. Results vary, with several being of poor quality; however, delirium at ED presentation may have a significant effect on long-term outcomes. Delirium is a significant concern in the ED, with many delirious patients not identified by physicians. Given the scale, addressing delirium should be a priority for clinicians and researchers. To improve delirium outcomes and hospital management, measures must include mechanisms to improve detection. Finding a single validated assessment method and facilitating research in this difficult patient population would be an important progress.

  • Delirium
  • systematic review
  • occurrence
  • acute confusion

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Delirium is well reported in the literature as common in many hospital settings.1 It is a mental disorder with serious adverse outcomes. A reported 10%–30% of general hospital admissions develop delirium, with a prevalence of between 30% and 60% in the elderly inpatients.1 However, delirium is frequently undetected and misdiagnosed in the clinical setting.2 Recent multidisciplinary commissions have identified the detection of delirium in the emergency department (ED) as a ‘high yield’ research objective.3–5

Delirium has significant adverse outcomes: death rates are increased, functional abilities reduced, admission to long-term care increased and length of stay increased.1 Impairment of cognitive function can persist for greater than 1 year, as can the symptoms of delirium, especially inattention, disorientation and impaired memory.1

With over 20 million attendances per year in England,6 EDs are the gateway to the general hospital. There is a great challenge in providing rapid, appropriate treatment in the first hours, and effective early diagnosis and treatment have been shown to make important differences to outcomes.

Despite its clinical importance, there is little documentation regarding delirium prevalence and physician detection rates within the emergency setting. The diagnostic criteria for delirium have been formulated in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV7) and in the tenth edition of the International Classification of Diseases (ICD-108). Core features include: disturbance of consciousness, disturbance of cognition, rapid onset, fluctuating course and external causation7–9 (the syndrome can be attributed to an independently diagnosable cerebral or systemic disease or disorder). The production of standardised research instruments has been seen to improve diagnostic consistency (online supplementary appendix 1), but under-recognition remains a problem. The detection of delirium within the emergency setting would be the key to targeting interventions and reducing the associated economic burden.

A necessary first step to devising appropriate strategies to prevent and manage delirium is to determine its occurrence and detection within the emergency setting. This will have implications in the planning and evaluation of any intervention. The cost per case and predictive value of screening will depend on how common it is in that setting.


The objectives are to determine the prevalence and physician detection rates of delirium in patients presenting to emergency care settings through a systematic review of the literature.

Identification of delirium

Identification of delirium has been the subject of many published papers. In a recent JAMA paper, Wong et al 10 systematically review the evidence on the accuracy of bedside instruments in diagnosing delirium in adults in hospital inpatients. The conclusions state that the best evidence supports the use of the confusion assessment method (CAM). In literature from the ED, Monette et al has been widely referenced as a validation of the CAM, sighting sensitivity and specificity of 95%.11

This systematic review interrogates the individual studies presenting data on the prevalence of delirium in the ED, acknowledging the differences between inpatient and ED medicine.

Types of study

We included prospective cohort and cross-sectional studies, and excluded trials as they are not representative of the target population. Studies of population groups where patients were judged to be in an emergency care setting, with the facility providing secondary care, were used. Studies based in community or hospice settings and inpatient environments were excluded. Studies in mixed populations were only included if data for general emergency care patients were reported separately, and results for this subset only were included in the analyses. We included studies using a case definition consistent with current consensus criteria for delirium and all its subtypes.

Retrospective studies in this area were excluded as it has been shown in the literature that a retrospective review of charts will fail to detect approximately two-thirds of patients with delirium.12

Delirium tremens was excluded from this review; although this is an important cause of delirium, it was judged to be a sufficiently distinct condition to warrant a separate review.


Systematic data extraction and assessments of quality were carried out. All studies considered for inclusion were examined by a second reviewer. Complete agreement was found.

There is a variety of descriptive terms in the literature. Incidence rates represent new events, and prevalence represents existing events. In clinical practice, distinction may be problematic, particularly in transient or fluctuating conditions, where the frequency of examination will have a major impact on reported rates. Feinstein suggests the term ‘occurrence rate’ to avoid some of these ambiguities.13 This is used wherever incidence or prevalence has not been clearly determined.

Search strategy

The latest search was conducted on 17 May 2012 by the primary author. Databases included: Medline, EMBASE, PsycINFO and CINAHL. Mesh and text terms were used (online supplementary appendix 2). Reference lists of retrieved articles, reviews and books were examined. Experts in this field were contacted and the internet searched for further references. Attempting to reduce publication bias, unpublished studies were searched using the internet and through experts in the field. Non-English papers were translated where possible using online translation.


Prevalence, incidence and occurrence studies

The search produced 723 citations of potential relevance, and following examination of titles and abstracts, 31 full-text articles were retrieved for further consideration. In all 18 were excluded: six described non-ED settings;14–19 three were reviews with no primary data;20–22 three were retrospective studies;23–25 one excluded cognitive impairment at the outset;26 and in five, the incidence, prevalence or occurrence of delirium was not determined or reported.27–31

Thirteen papers met the inclusion criteria.32–44 Several papers were written by the same authors. Three papers by Han et al appear to comment on the same data set (although the inclusion dates differ).34–36 Also, two publications by Hustey et al are likely to comment on the same data set.37 ,38 Results for the occurrence of delirium in the emergency setting were therefore available for 10 cohorts (online supplementary table 1).


All studies were carried out in the emergency setting, predominantly in general hospitals. Eleven studies were from general hospital EDs, one was from a private hospital ED42 and one was from a neurological ED.43

All studies were prospective. One data set was used from a separate multi-centre case-control study,40 one study was an audit on five weekday mornings33 and one was an interventional study.39 The remainder were observational cohort studies.32 ,34–38 41–44 All used consecutive convenience samples.

Inclusion and exclusion criteria were broadly similar, with most studies excluding subjects due to refusal, critical illness, inability to communicate or cooperate at time of study and non-English/French speaking in absence of an acceptable translator. Most only included the initial visit for patients presenting to the ED more than once.

Three studies excluded subjects with severe dementia specifically,34–36 suggesting that people who were not able to follow simple commands at baseline classified as dementia. Other exclusion criteria such as pre-existing confusion, difficulty completing interviews or cognitive impairment were taken to exclude dementia in the remaining studies.

Twelve studies were carried out in older populations, with six assessing people aged 65 and over,32–36 ,43 two assessing people aged 66 over,40 ,44 and four assessing people aged 70 and over.37–39 ,44 One study sampled all adult patients.43

Methods to obtain consent and reporting of response rates varied considerably; this is discussed later.

Results for delirium prevalence, incidence and occurrence

Twelve studies reported delirium prevalence at admission, with assessments undertaken within their ED visit. In one study delirium was reassessed every 24 h in the ED, and participants would be included in the delirious group if their scoring changed.43

Two of the studies assessed patients within 6 h,38 ,39 three indicated delirium assessment had been undertaken within 12 h of admission29–31 and the remaining had no time from admission stated.

Occurrence rates for delirium were given or could be derived from presented data in all 13 studies.

Published occurrence rates of delirium at admission ranged from 7% to 20%.

Methodological differences and limitations

There are significant differences with methodology encountered in all included papers. This limits the evidence and hinders the transferability of results of the included studies.

Delirium screening and diagnostic methodology differed, with heterogeneity in the measures used to describe delirium occurrence. Procedures to obtain consent also differed, and there is variability in the methodological quality of studies.

As expected there were variable selection criteria, which is inevitable in multiple studies; however, the concerning feature of some of the studies is high exclusion rates, with Elie et al,32 Han et al 36 and Kakuma et al 40 excluding approximately a third of the sample.

The length of study also varied dramatically, and the smallest study (Hare et al 33) was undertaken over five mornings in the form of an audit. The larger studies were performed over 12–16 months; however, only studies by Hustey et al37–39 performed 24 h recruitment. The 24 h nature of emergency medicine means that to demonstrate a representative sample, data collection must be performed accordingly.

Non-validated reference standards were also used widely in the included papers. Four of the studies used the non-ED validated Confusion assessment method for the intensive care unit (CAM-ICU).34–36 ,42 One used the Delirium Rating Scale,43 and the remainder used the CAM. Although Monette et al is widely referenced as an ED validation of the CAM,11 there are significant issues with this study. This trial actually assessed agreement between a geriatrician and a lay researcher over the geriatrician's assessment of selected delirious patients in the ED; it did not directly assess the CAM as a screening tool.

The sensitivity and specificity of diagnostic instruments have been shown to vary depending on the training and professional background of the administrator.45 Again, studies differed in the use of researchers and clinicians employed in case ascertainment. A systematic review by Wong et al reported that the positive likelihood ratio for the CAM was significantly higher when it was administered by physicians than nurses.10 Only research by Elie et al 32 and Ramirez-Bermudez et al 43 was performed by physicians, and the remainder performed by either a research nurse or research assistant. Interestingly, the physicians were not ED trained.

Time lag of initial assessment also varied between the studies. As mentioned above, two studies assessed patients within 6 h,43 ,44 three assessed within 12 h of admission34–36 and the remaining had no time from admission stated. Ideally to assess the prevalence of delirium in the ED, assessment should be undertaken at presentation. As delirium can be an evolving state, assessment following prolonged admission may affect the reliability of the data presented.

Distinction between delirium and dementia cases was also problematic in some studies. However, most (12) of the studies used the CAM or CAM-ICU tool which has been shown to differentiate between delirium and dementia.45

The three studies by Han et al used the Informant questionnaire on cognitive decline in the elderly (IQCODE), Mini mental state examination (MMSE) or medical record to identify dementia.34–36 While the MMSE is an accepted criterion standard for diagnosing dementia, neither the MMSE nor the IQCODE has ever been validated in ED settings.

The remaining study which was carried out in a Mexican neurological emergency setting used the Delirium rating scale (DRS),43 known for its capacity to distinguish between delirium and other neuropsychiatric syndromes (psychosis and dementia), with a high diagnostic validity. However, there is no certainty that any of the included studies excluded all patients with dementia.

The presence of comorbid conditions was not reported in most studies. Where comorbidity was documented, the results were heterogeneous. This was also seen when the final diagnosis was reported.

This systematic review does not attempt to present data on causation of delirium presentations to the ED, but highlights the burden of disease in the ED.

Results for delirium identification

Eight of the studies presenting data on prevalence of delirium also reported on physician recognition of delirium32 ,35 ,37–42 (online supplementary table 2). Two studies commented on the specificity of physician diagnosis.32 ,39

Seven of the studies used retrospective case-note analysis to determine identification of delirium by the ED physician.32 ,35 ,37 ,38 ,40–42 This primarily took the form of reviewing the case notes from prescreened patients looking for reference to terms associated with delirium. This is a suboptimal form of data gathering as it does not accurately assess detection of delirium. The physician may have identified delirium, which however was not documented as such.

One study by Hustey et al 39 (n=271, delirium prevalence 7%) prospectively assessed the physician using interviews to assess for recognition of mental status impairment. Physicians were initially blinded to the screening results, then unblinded following assessment and interview. Results showed that only 16% (95% CI 3% to 40%) of patients with delirium were identified by the physician (specificity 98%, 95% CI 96.0% to 99.6%). Interestingly, knowing the screening results prompted no change in physician management. However, there were several problems with this study. Although commonly sighted, the CAM is not a validated reference standard. There is no information about who applied the reference standard and a lack of information about when the patient was assessed.

Physician diagnosis rates of cases of preconfirmed delirium (using a specified tool) within the ED varied between 11.1%42 and 46.0%.38

One study by Kakuma et al 40 addressed discharged ED patients. They found that of the discharged delirious patients, 56.7% of these had been detected in the ED. This is interesting as it underlines that even though patients with delirium are being detected, this does not necessarily trigger admission.

Measures for physician detection of delirium varied widely from prospective assessment (prior to physician consultation) to re-interview of patients to case-note review. This must be considered when interpreting the figures.

A consideration for all the studies addressing recognition of delirium is that the potential underlying cause for delirium may have been documented by the ED physician. Although identification of the underlying cause is advantageous, the identification of delirium is equally important in identifying targets for delirium interventions. In the UK, the National Institute for Health and Clinical Excellence (NICE) guidelines for delirium highlight this point, stating that delirium should be documented both in the patient's hospital record and in their primary care health record.9


This literature review found that published delirium occurrence rates in emergency settings range from 7% to 20% in the elderly patients. It also shows maximal physician detection rates of 24% of delirious patients.

The limitations of this review were identified. We used a broad search strategy, imposing no language restrictions for included studies, but did confine searches to databases provided in the English language. Resource limitations also meant that it was not possible to independently review all citations or abstracts identified by the original search. Nevertheless, we believe the review was sufficiently comprehensive to identify most important findings in this area.

It is clear from this review that delirium is common in EDs. Early detection and intervention for patients with delirium would be a logical step in attempting to reduce the burden of disease.

The results are even more striking given that they are likely to be an underestimate due to the exclusion of critically ill patients, individuals who are unable to communicate and patients who did not have a proxy present for confirmation of altered mental state. This is an integral consideration when addressing delirium in the emergency setting. Many of the studies identified are limited by convenience sampling, and lack of 24 h sampling, making the true prevalence of delirium unknown.

The single major risk factor for delirium is dementia. In excluding individuals with dementia from the studies, this significantly affects the true portrayal of delirium occurrence. It is estimated that of the 820 000 people in the UK with dementia, almost 385 000 people are living without a diagnosis.46 Further research estimates that more than a million people in the UK will have dementia by 2021 and 6 in 10 (60%) will not be aware they have the condition.46 These figures highlight how vital the investigation of delirium is. Identifying delirium in the emergency setting will identify individuals who have an undiagnosed dementia. With increased prevalence of dementia, it is reasonable to suggest that higher numbers of patients will suffer from delirium and hence the incidence of delirium seen within the emergency setting will increase. Therefore, the skills of identification and prompt, appropriate management are vital for anyone based in the emergency setting.

Clinical implications and planning

Recent recommendations from researchers, educators and policy makers within the Society for Academic Emergency Medicine and the American College of Emergency Physicians have identified the detection of delirium in the ED as a high yield research objective.3–5

To improve delirium outcomes and hospital management, measures must include mechanisms to improve its detection. There is an important transition between research results and results guided service implementation. The research field of delirium in the ED requires movement into intervention research to attempt to address the likely increasing presentations of delirium in the ED.

One interesting study by Carpenter et al investigated the use of geriatric screening within the ED.47 They used geriatric technicians to screen for cognitive dysfunction. This is an interesting concept that could be used to filter patients and refer to specialist services.

It is important to acknowledge the pressures of the ED, where there are significant difficulties in diagnosing and managing delirium. The requirement to rapidly assess patients in the changing environment, with often little information about the normal functioning of patients, and little time to assess patients over time, makes identification of delirium difficult.

A concerted effort for increasing knowledge and skills throughout the whole multidisciplinary team must be made. Mental health services may have a role by offering education, training and advice to staff, as well as consultation for more complex management problems.

Given the scale of the problem and the pressures present within the emergency setting, interventions and screening tools need to be simple and quick to undertake. The balance between a necessarily comprehensive and yet practicable intervention is difficult but must be achieved with particular attention to addressing issues of implementation and adherence.48

Early detection and anticipation of risk of delirium is important in patient care. Recent studies have shown that delirium is common in nursing homes.49 Moreover, admission from an institution rather than the community is a risk for delirium in hospital.50 Intervening in these settings could have the potential to deliver important benefits, including reducing hospital admissions, and therefore needs evaluation.

Other barriers to improving clinical quality exist. Identifying an individual's previous cognitive state can be difficult, especially where there is no family or regular carers present at presentation. Currently in the UK there are no shared data systems between mental health trusts and the acute hospitals. This would seem to be archaic in the modern working environment where maximal information is vital to ongoing management of patients, and information technology is abundant. Universal access to data records for health professionals would help to identify individuals who have been reviewed by mental health services and would be able to guide on a patient's normal cognitive state.

Guidelines have however been implemented to try and capture the majority of delirium cases. The UK NICE guidelines advise that when there is uncertainty regarding a diagnosis of delirium, the patient should be treated as if he or she has delirium and the appropriate investigations undertaken.9

Outcome studies

While not the primary focus of this review, it is interesting to look at outcome studies. Only four delirium outcome studies have been conducted in the ED setting.

Kakuma et al addressed a small subset (n=103) of patients discharged from the ED.40 Those discharged with delirium (n=30, identified by the CAM) had a statistically significant increased 6-month mortality. However, no statistical difference was seen at 18 months.

Lewis et al found that patients with delirium were significantly more likely to die at 3 months (14% vs 8%), but their analysis did not adjust for confounders.41

Han et al addressed patients who were admitted and discharged, finding that patients who were delirious in the ED were more likely to die at 6 months compared with non-delirious patients (36% vs 10%).36 This relationship was independent of age, comorbidity and severity of illness. However, they did not incorporate confounders such as dementia and functional impairment in their multivariable model.

Vida et al investigated the relationship between delirium and long-term functional outcomes.44 They reported that delirium in the ED was associated with accelerated functional decline at 18 months in patients without pre-existing dementia. However, this association disappeared after adjusting for confounders.

Hence from the available sources, delirium at ED presentation may have a significant effect on long-term outcomes; however, further studies should address causation and mortality associated with delirium at ED presentation.


A Cochrane review investigated interventions for preventing delirium in hospitalised patients.1 They found that research evidence on effectiveness of interventions to prevent delirium is sparse.

Although little evidence exists, interventions for preventing delirium in hospitalised patients have been developed. Most of the current studies have taken a multi-factorial approach, attempting to prevent several risk factors by protocols, education or systems redesign, rather than focusing on one risk factor in isolation.51–53 Clearly further research is required in the area of delirium prevention in general; however, as early detection would suggest decreased morbidity and mortality it is cogent to suggest that some of this research be directed to the ED.

Research implications

Throughout these studies there was heterogeneity in case-finding and methods for establishing diagnosis. Despite the consensus in diagnostic criteria, Laurila et al 54 have shown how much variability is introduced simply by applying different DSM and ICD-10 criteria to the same data set. Hence establishing a single validated delirium assessment method for the emergency setting is a vital first step to improved management (online supplementary appendix 1).

Mower addresses bias and variability in diagnostic tests,55 identifying that many diagnostic tests are not rigorously evaluated before general application. Studies examining test characteristics often have methodological flaws which can introduce systematic biases that distort test accuracy. Design errors make it difficult to generalise results of individual studies, enhancing performance of poor tests while obscuring the performance of good tests. This may lead to widespread use of tests with uncertain or limited efficacy.

The most important problem with all of the primary literature found on delirium is the exclusion of members of the target population. This occurs because exclusion criteria often include properties of the index condition. Delirium may affect people's ability to consent, communicate or complete interviews, and selection criteria requiring these conditions will obviously differentially exclude more subjects with delirium.

This is increasingly important as dementia is the biggest single risk factor for delirium. Excluding individuals with dementia invariably excludes individuals with delirium. As delirium is a poor prognostic factor for dementia early identification is vital. In practice, it may be important to identify patients with both delirium and dementia in the ED.

The ethical conduct of research in potentially cognitively impaired patients is a complex issue. Ethical considerations exist when addressing both dementia and delirium. This includes issues of conducting research in unrepresentative study populations. However, this review highlights the high occurrence of delirium within the ED and the low physician recognition rates. Although ethical considerations must not be dismissed, with the burden of disease in the ED clearly identified, it is vital that research is directed towards delirium.

Most of the evidence about delirium prevention and management is from North America, with no studies identified in this review from Europe. This is possibly because healthcare systems there are much more accurately costed than in Europe, with more awareness of the economic impact of delirium.

The promising health service research centring on multi-component interventions for delirium is difficult to deliver on the large scale required. However, for evidence based healthcare systems to develop and deliver optimal services, research must be supported and funded in these difficult areas now to reduce morbidity and mortality in the years to come.


Delirium is a significant problem in the emergency setting. The recorded occurrence is up to 20% in the elderly patients; however, the detection of delirium is low (up to 24%). There are many methodological and ethical concerns which have impeded delirium research and as such the figures reported are likely to suffer from under-reporting. The published research is predominantly from North America, with no published data from Europe. Given the scale of the problem, addressing the issue of delirium should be a priority for clinicians and researchers. Finding a single validated assessment method and facilitating research in this difficult patient population would be an important move forward.


Supplementary materials


  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.