Orientation to time as a guide to the presence and severity of cognitive impairment in older hospital patients.

BACKGROUND: Testing of orientation to time is an important part of mental status examination. The validity of errors in different aspects of temporal orientation was examined in older hospital patients as a guide to the presence of dementia or delirium and as a measure of the severity of dementia, as defined by the Global Deterioration Scale.
METHODS: Inpatients and outpatients attending an acute hospital underwent independent assessments by two doctors on the same day to determine orientation to time and cognitive status. Optimum cut-offs for error scores on the different aspects of temporal orientation were calculated to maximise the sum of sensitivity and specificity for detection of dementia or delirium.
RESULTS: Of the 262 patients assessed, 62 (23.7%) had dementia or delirium. The best cut-offs for detection of these disorders were: any error in identifying the year, month, day of the month or day of the week; and an error of more than 1 h in identifying the time of day. Failure to identify the year correctly was the most valuable single sign of dementia or delirium (sensitivity 86% and specificity 94%); failure to identify either year or month correctly was 95% sensitive and 86.5% specific for the detection of cognitive impairment. Severity of temporal disorientation, measured using a number of approaches, was strongly associated with severity of dementia.
CONCLUSION: Disorientation to time is a useful guide to the presence and severity of dementia or delirium in older hospital patients. Failure to identify the year or month correctly is a sufficiently sensitive and specific indicator of dementia or delirium to warrant more detailed cognitive assessment in this population.