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BackgroundTo date, delirium prevalence and incidence in acute hospitals has been estimated from pooled findings of studies performed in distinct patient populations.ObjectiveTo determine delirium prevalence across an acute care facility.DesignA point prevalence study.SettingA large tertiary care, teaching hospital.Patients311 general hospital adult inpatients were assessed over a single day. Of those, 280 had full data collected within the study's time frame (90%).MeasurementsInitial 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.ResultsUsing 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.ConclusionsOur 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.

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Clinical subtyping of delirium according to motor-activity profile has considerable potential to account for the heterogeneity of this complex and multifactorial syndrome. Previous work has identified a range of clinically important differences between motor subtypes in relation to detection, causation, treatment experience and prognosis, but studies have been hampered by inconsistent methodology, especially in relation to definition of subtypes. This article considers research to date, including a number of recent studies that have attempted to address these issues and identify a means of achieving greater consistency in approaches to subtyping. Possibilities for future work are discussed and a research plan for the field is outlined.