The diagnosis, prevalence and outcome of delirium in a cohort of older people with mental health problems on general hospital wards.

OBJECTIVES: This paper aimed to measure the prevalence and outcomes of delirium for patients over 70 admitted to a general hospital for acute medical care and to assess the validity of the Delirium Rating Scale-Revised-98 (DRS-R-98) in this setting.
METHODS: Prospective study in a British acute general hospital providing sole emergency medical services for its locality. We screened consecutive patients over 70 with an unplanned emergency hospital admission and recruited a cohort of 249 patients likely to have mental health problems. They were assessed for health status at baseline and followed over 6 months. A sub-sample of 93 participants was assessed clinically for delirium.
RESULTS: 27% (95% confidence interval (CI) 23-31) of all older medical patients admitted to hospital had DRS-diagnosed delirium, and 41% (95% CI 37-45) had dementia (including 19% with co-morbid delirium and dementia). Compared with clinician diagnosis, DRS-R-98 sensitivity was at least 0.75, specificity 0.71. Compared with reversible cognitive impairment, sensitivity was at least 0.50, specificity 0.67. DRS-diagnosed delirium was associated with cognitive impairment, mood, behavioural and psychological symptoms, activities of daily living, and number of drugs prescribed, supporting construct validity. Of those with DRS-diagnosed delirium, 37% died within 6 months (relative risk 1.4, 95% CI 0.97-2.2), 43% had reversible cognitive impairment, but only 25% had clinically important recovery in activities of daily living. Behavioural and psychological symptoms were common and mostly resolved, but new symptoms frequently developed.
CONCLUSION: Delirium is common. Some, but not all, features are reversible. DRS-R-98 has reasonable validity in populations where co-morbid dementia is prevalent.