THE INCIDENCE OF DELIRIUM IN PSYCHIATRIC INPATIENT UNITS

Objectives: To estimate prospectively the incidence of delirium in psy chiatric inpatients and to identify risk factors for delirium in this population. Method: The subjects were nondelirious patients newly admi tted to the Calgary General Hospital. The Delirium Symptom Interview ( DSI), the Confusion Assessment Method (CAM), and the Mini-Mental State Examination (MMSE) were used to identify incident cases of delirium. In order to evaluate the potential impact of selection bias, we conduc ted ct supplementary analysis using record linkage to an electronic ad ministrative data base with coverage of the target population. Results : Of 420 admissions to the hospital 401 subjects provided informed con sent and were not delirious at the time of admission. There were 9 inc ident cases of delirium. The cumulative incidence rate was, therefore, 2.14 per 100 admissions. The record linkage analysis did not uncover evidence of selection bias. Delirium was associated with a significant ly increased length of stay in hospital. Conclusions: Delirium is an u ncommon incident event in psychiatric inpatient population. The incide nce rate reported here may be useful as a benchmark the identification of excessive rates in other inpatient settings. Since delirium is som etimes related to modifiable therapeutic factors, an excessive rate sh ould prompt a search for its causes.