Sicker Patients Get Checked: Why Hospitals Miss Delirium in Their ‘Healthiest’ Older Patients

Delirium is one of the most common and most dangerous complications of hospital care in later life, yet new research suggests that the patients most likely to be checked for it are not always the ones clinicians might expect. A study of more than 6,000 hospital admissions of people aged 75 and over has found that fewer than half had any documented delirium screening, and that the odds of being screened rose steadily with the number of long-term conditions a patient carried. Paradoxically, those with the fewest chronic illnesses, and those admitted for planned operations rather than emergencies, were the most likely to slip through the net.

The research, published in European Geriatric Medicine by a team led by Sarah J. Richardson of Newcastle University and the NIHR Newcastle Biomedical Research Centre, drew on routinely collected electronic health record data from Newcastle upon Tyne Hospitals NHS Foundation Trust, one of the largest hospital trusts in the United Kingdom, with roughly 1,700 inpatient beds across two sites. The analysis covered all index admissions of people aged 75 or older between 1 April 2021 and 31 October 2021, a total of 6,068 admissions. The work forms part of a wider programme by the ADMISSION Research Collaborative, an initiative funded to tackle multimorbidity at scale using large-scale clinical data.

Delirium itself is an acute, fluctuating disturbance of attention, arousal and cognition that predominantly strikes older people in hospital. It is distressing for patients and families, strongly associated with poor outcomes including higher mortality, and extraordinarily costly: a recent policy analysis estimated that delirium cost the NHS £10.8 billion in 2022 alone. National guidance recommends that everyone aged 65 and over be screened for delirium on admission to hospital, and higher screening rates are strongly linked to higher rates of diagnosis. Yet the largest point prevalence study of delirium detection in the UK found that only 27.3 percent of older inpatients were screened. Patients in whom delirium is missed fare measurably worse, experiencing higher mortality than those in whom the condition is recognised.

The Newcastle team set out to ask whether a patient’s burden of multiple long-term conditions, often abbreviated MLTC and also known as multimorbidity, influenced whether delirium screening was documented. Multimorbidity, defined as the coexistence of two or more chronic conditions in one individual, is rising in prevalence worldwide and has been identified as a global research priority. It is a recognised risk factor for developing delirium and worsens outcomes after delirium occurs, but no previous study had examined whether it shapes the screening process itself. To operationalise the concept, the researchers used the ADMISSION collaborative’s standardised framework of 60 long-term conditions, each defined by lists of ICD-10 diagnostic codes drawn from the index admission and up to ten years of prior records. This approach deliberately treats multimorbidity as a continuum, analysing the number of conditions rather than a simple present-or-absent cut-off, in line with earlier work showing that outcomes scale with condition count.

Delirium screening at the trust is implemented through a non-mandatory, clinician-initiated electronic form embedded in the electronic health record. The form asks whether the patient has a clinical diagnosis of delirium and instructs clinicians to use the 4AT assessment tool alongside clinical judgement. Local policy mandates screening for everyone aged 75 and over, whether admitted electively or as an emergency. For the purposes of the study, screening documentation was deemed complete if the form existed at all; the researchers did not assess how thoroughly the form was filled in, the outcome of screening, or whether the screening itself was accurate.

The headline numbers were sobering. Delirium screening documentation was completed in only 42.7 percent of admissions, 2,594 of 6,068. The gap between admission types was stark: 48.6 percent of emergency admissions had documented screening, compared with just 28.2 percent of elective admissions. The cohort had a median age of 82 years, and 52 percent were women. Multimorbidity was highly prevalent, as expected in a hospitalised older population, and patients admitted electively carried fewer long-term conditions on average than those admitted as emergencies. Older age, emergency admission, female sex, living in the most deprived neighbourhoods as measured by the Index of Multiple Deprivation, and increasing numbers of long-term conditions were all associated with higher odds of screening documentation, and similar patterns held when elective and emergency admissions were analysed separately.

The finding that a greater burden of chronic disease predicts a greater likelihood of screening has not been reported before, but it aligns with earlier evidence that multimorbidity increases the chance of delirium symptoms being noted in nursing documentation. The authors suggest a plausible mechanism: multimorbidity correlates with greater delirium severity, which may make symptoms more obvious to clinical teams and prompt the completion of screening. By contrast, patients with fewer long-term conditions, and those arriving for planned procedures, may be implicitly judged by staff to be fitter and at lower risk of delirium. This informal risk stratification, the researchers argue, may be quietly depressing screening rates in precisely the groups where it should not. That matters because post-operative delirium rates after elective surgery are high, and screening in elective admissions is vital even when patients appear robust on arrival.

How do these figures compare with the wider landscape? The emergency admission screening rate of 49 percent matches rates reported from a large teaching hospital in Salford, England, and sits well above the 27.3 percent recorded in the UK-wide point prevalence study of 45 hospitals. But it falls far short of the 77 percent achieved in emergency admissions in Edinburgh, Scotland, demonstrating that high screening rates are achievable and that wide regional variation persists. The authors note that consistently high screening is the exception rather than the rule, which underscores the importance of understanding the factors that hold screening back at lower-performing sites, including the subtle patient-level biases documented in this study.

The study has notable strengths, including the large cohort size and the inclusion of both elective and emergency admissions, a group frequently under-represented in analyses of routine data. The use of agreed, standardised definitions of multimorbidity designed specifically for hospital data is another methodological advance. Limitations remain, however. The team could only examine the completion of screening documentation, not screening itself or its accuracy, because of constraints in the available data. Local policy screening only those aged 75 and over, rather than 65 as national guidance recommends, may limit generalisability, as may the fact that the data window fell during the COVID-19 pandemic. The analysis was deliberately descriptive, focused on clinician behaviour, and future work with multivariable modelling will need to address confounding, including measures of frailty, though the authors caution that frailty definitions built for routine data overlap heavily with multimorbidity counts and require careful handling.

The practical message is clear and potentially actionable for hospitals everywhere. Delirium screening needs to improve for all older inpatients, because missing the diagnosis carries serious consequences, but improvement efforts should explicitly target the groups identified here: people with fewer long-term conditions and those admitted electively. Embedding screening as a default, mandatory step in the electronic record, decoupled from staff impressions of who looks like a delirium risk, could help close the gap. As populations age and multimorbidity becomes the norm rather than the exception, ensuring that every older patient, whatever their apparent fitness, receives a simple, validated cognitive check on admission may be one of the highest-value interventions available to hospital systems, with the potential to avert deaths, shorten stays and spare families the distress of an overlooked, treatable brain failure.

Subject of Research: The influence of multiple long-term conditions on delirium screening documentation in hospitalised older adults, analysed using routinely collected electronic health record data.

Article Title: Understanding the impact of Multiple Long-Term Conditions (MLTC) on the completion of delirium screening documentation: analysis using routinely collected clinical data

Article References: Richardson, S. J., Bunn, J. G., Evison, F., Gallier, S., Harris, S., le Roux, P., Plummer, C., Prendergast, E., Sapey, E., Sayer, A. A., Singer, M., Shahmandi, M., Witham, M. D., & on behalf of the ADMISSION Collaborative (2026). Understanding the impact of Multiple Long-Term Conditions (MLTC) on the completion of delirium screening documentation: analysis using routinely collected clinical data. European Geriatric Medicine. https://doi.org/10.1007/s41999-026-01594-9

Image Credits: AI Generated

DOI: 10.1007/s41999-026-01594-9

Keywords: delirium, screening, multimorbidity, multiple long-term conditions, older people, electronic health records, hospital admissions, 4AT, geriatrics, elective admission, emergency admission, routinely collected data