Measures of the Clinical Course of Delirium

Using the Delirium Index, delirium was defined (based on DSM-III-R criteria) as the presence of disorders of attention and thought, and disorders of any 3 of the following: consciousness, orientation, memory, perception, and psychomotor activity. We constructed 5 measures of the in-hospital clinical course of delirium during the first 28 days from diagnosis.

1. The duration of the initial delirium episode was defined as the time from diagnosis to either the absence of delirium at 2 consecutive assessments or absence of delirium at one assessment and no further in-hospital assessments (due to discharge or withdrawal). In each case, the date of recovery was estimated at the mid-point between the last positive (with delirium) and the first negative (no delirium) assessment. Among patients who were discharged or withdrew before 28 days from enrollment with delirium at the last assessment before discharge or withdrawal, the duration of the episode was considered to be the time from enrollment to discharge. Among patients who were still in hospital at 28 days, the results of the first DI assessment after 28 days was considered in the definition of duration of the episode.

2. The number of days with delirium was estimated as follows. All the days between 2 consecutive positive assessments were considered to be positive, and all the days between 2 consecutive negative assessments were considered to be negative. Half of the days between 2 consecutive assessments, one of which was positive and one negative, were considered to be positive. Among patients who were discharged or withdrew before 28 days from enrollment with delirium at the last assessment before discharge or withdrawal, the patient was considered to have delirium on all the days between the last assessment and discharge or withdrawal, for a maximum of 28 days. Among patients who were still in hospital at 28 days, the results of the first DI assessment after 28 days were considered in the definition of delirium days.

3. The proportion of days with delirium was computed as the number of days with delirium (from 2 above) divided by the duration of observation, from enrollment up to the date of discharge or withdrawal or 28 days from enrollment, whichever was shorter.

4. The time to cognitive improvement was defined as the time to an increase in the MMSE score of 2 or more points compared to baseline, with no subsequent decrease below the baseline score plus 2 points. If the baseline MMSE score was 27 or more, patients whose MMSE score did not decline below 27 in subsequent assessments were considered to have improved in 0.5 days.

5. The in-hospital course of delirium was a 3-category measure: transient (recovery within 24 hours); recovered (recovery between 24 hours after diagnosis and discharge or at 8 weeks if patient was still in the hospital); and persistent (delirium present at discharge or at 8 weeks if patient was still in the hospital).

MMSE, Mini-Mental State Examination.