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Delirium in an adult acute hospital population: predictors, prevalence and detection
  1. Daniel James Ryan1,
  2. Niamh Annmarie O'Regan1,
  3. Ronán Ó Caoimh1,
  4. Josie Clare2,
  5. Marie O'Connor3,
  6. Maeve Leonard4,
  7. John McFarland5,
  8. Sheila Tighe6,
  9. Kathleen O'Sullivan7,
  10. Paula T Trzepacz8,9,
  11. David Meagher4,
  12. Suzanne Timmons1
  1. 1Centre for Gerontology and Rehabilitation, University College Cork, St. Finbarr's Hospital, Cork, Ireland
  2. 2Department of Medical Gerontology, Waterford Regional Hospital, Waterford, Ireland
  3. 3Department of Geriatric Medicine, Cork University Hospital, Cork, Ireland
  4. 4Department of Psychiatry, University of Limerick, Limerick, Ireland
  5. 5Clare Mental Health Services, Ennis Regional Hospital, Clare, Ireland
  6. 6Department of Psychiatry, University Hospital Limerick, Limerick, Ireland
  7. 7School of Mathematical Sciences, University College Cork, Cork, Ireland
  8. 8Department of Neurosciences, Lilly Research Laboratories, Indianapolis, Indiana, USA
  9. 9Indiana University School of Medicine, Indianapolis, Indiana, USA
  1. Correspondence to Dr Niamh O'Regan; niamh.oregan{at}


Background To date, delirium prevalence and incidence in acute hospitals has been estimated from pooled findings of studies performed in distinct patient populations.

Objective To determine delirium prevalence across an acute care facility.

Design A point prevalence study.

Setting A large tertiary care, teaching hospital.

Patients 311 general hospital adult inpatients were assessed over a single day. Of those, 280 had full data collected within the study's time frame (90%).

Measurements Initial screening for inattention was performed using the spatial span forwards and months backwards tests by junior medical staff, followed by two independent formal delirium assessments: first the Confusion Assessment Method (CAM) by trained geriatric medicine consultants and registrars, and, subsequently, the Delirium Rating Scale-Revised-98 (DRS-R98) by experienced psychiatrists. The diagnosis of delirium was ultimately made using DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) criteria.

Results Using DSM-IV criteria, 55 of 280 patients (19.6%) had delirium versus 17.6% using the CAM. Using the DRS-R98 total score for independent diagnosis, 20.7% had full delirium, and 8.6% had subsyndromal delirium. Prevalence was higher in older patients (4.7% if <50 years and 34.8% if >80 years) and particularly in those with prior dementia (OR=15.33, p<0.001), even when adjusted for potential confounders. Although 50.9% of delirious patients had pre-existing dementia, it was poorly documented in the medical notes. Delirium symptoms detected by medical notes, nurse interview and patient reports did not overlap much, with inattention noted by professional staff, and acute change and sleep-wake disturbance noted by patients.

Conclusions Our point prevalence study confirms that delirium occurs in about 1/5 of general hospital inpatients and particularly in those with prior cognitive impairment. Recognition strategies may need to be tailored to the symptoms most noticed by the detector (patient, nurse or primary physician) if formal assessments are not available.

  • Geriatric Medicine
  • Mental Health
  • Epidemiology
  • Internal Medicine
  • Medical Education & Training

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: and

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