Do the Phenotypes of Symptom Fluctuation Differ Among Motor Subtypes in Patients With Delirium?

Abstract

Fluctuation in symptoms is a core feature of delirium. However, it is not well known whether the fluctuating nature would differ or not among the delirium subtype groups. This study compared phenotypes of diurnal fluctuation among different delirium subtypes using a prospective design. The motor subtypes of delirium patients were determined using the Delirium Motor Subtype Scale, fluctuations in consciousness levels were monitored with the Richmond Agitation-Sedation Scale (RASS), and symptom severity was assessed with the Nursing Delirium Screening Scale (Nu-DESC). All scales were administered at three time points over 24 hours; fluctuations in and phenotypes of symptoms were compared according to subtype of delirium using repeated-measures analysis of variance after adjustment for covariates. This study included 224 delirium patients. Of this patients, 144 (64.3%) were classified as hyperactive, 25 (11.2%) as hypoactive, 33 (14.7%) as mixed, and 22 (9.9%) as no subtype. Scores on the RASS and Nu-DESC significantly changed during the evening and/or night and there were significant subtype group × time interaction for the RASS and Nu-DESC (F = 9.66, P < 0.001 and F = 5.11, P < 0.001, respectively). Post hoc analyses revealed that the hyperactive and mixed subtype groups had higher mean RASS scores and greater ranges of fluctuation than the other groups. The mixed subtype group was differentiated from hyperactive and hypoactive subtype groups by the range of fluctuation in psychomotor activity. The phenotypes of symptom fluctuation differed among the motor subtypes. These findings further support the rationale that fluctuations are a core feature of delirium and could differentiate delirium subtypes.