Quantitative Analysis of Rest-Activity Patterns in Elderly Postoperative Patients with Delirium: Support for a Theory of Pathologic Wakefulness

Abstract

To investigate the feasibility of using wrist actigraphy in a postoperative cohort of elderly patients (delirious versus nondelirious), and to use actigraphy to help characterize diurnal rest-activity patterns in this population. This was a prospective postoperative study using wrist actigraphy and clinical scales (DRS-R-98 and Mini-Mental State Examination). Actigraphy was continuous for 24 to 72 hours, and scales were completed once daily. DSM-IV-TR criteria were used to diagnose delirium and to separate the sample into delirium and nondelirium groups. Groups were compared at inception (age, sex, time since surgery, number of medications, number of active medical conditions, and presurgical sleep quality). For actigraphy analysis, a 24-hour sample (taken when the DRS-R-98 score was highest) was used for each patient. Statistical analyses were performed on 6 rest-activity parameters to examine group differences. Thirteen patients were studied: 6 with delirium and 7 without delirium. The groups did not differ significantly at inception. Significant group differences were found in diurnal rest-activity patterns: delirious patients showed fewer nighttime minutes resting, fewer minutes resting over 24 hours, greater mean activity at night, and a smaller amplitude of change in activity from day to night. This is the first study to document a significant disruption of the diurnal rest-activity cycle among delirious patients using objective methods and quantitative analysis of activity. Rest and activity consolidation were significantly reduced in delirious patients, as was the amplitude of day-night differences in rest and activity. These findings are consistent with a state of pathologic wakefulness in delirium.