Impact of different diagnostic criteria on prognosis of delirium: a prospective study

A 2-year follow-up study was performed to compare the prognosis of delirium defined according to 4 different diagnostic classifications (DSM-III, DSM-III-R, DSM-IV and ICD-10 clinical criteria) among 425 elderly geriatric hospital patients and nursing home residents. The proportion of delirium varied from 24.9% (DSM-IV) to 10.1% (ICD-10). The prognoses were similar particularly according to all DSM classifications: 31.3-36.3% of the delirious patients died within 1 year and 57.8-62.5% within 2 years. The number of subjects diagnosed as delirious according to the ICD-10 was small, and their prognosis did not differ significantly from the others either. The DSM-IV has simplified the criteria of delirium. It identifies new, acutely ill and relatively nondependent subjects as delirious who share the poor prognosis of patients diagnosed with the previous criteria.