Circadian rest-activity misalignment in critically ill medical intensive care unit patients

Abstract

Circadian alignment of rest–activity rhythms is an essential biological process that may be vulnerable to misalignment in critically ill patients. We evaluated circadian rest–activity rhythms in critically ill patients and their association with baseline (e.g. age) and clinical (e.g. mechanical ventilation status) variables, along with intensive care unit light–dark cycles. Using wrist actigraphy, we collected 48-hr activity and light exposure data from critically ill patients in a tertiary care medical intensive care unit. We evaluated circadian rest–activity rhythms using COSINOR and non-parametric circadian rhythm analysis models, and stratified these data across baseline and clinical variables. We used linear regression to evaluate the association of circadian rest–activity and light–dark exposure rhythms. In COSINOR and non-parametric circadian rhythm analysis analyses, the 34 medical intensive care unit patients completing 48-hr actigraphy recordings exhibited mean MESOR (mean activity levels of a fitted curve) and amplitudes of 0.50 ± 0.32 and 0.20 ± 0.19 movements per 30-s epoch, with high interdaily variability. Patients who were older, mechanically ventilated, sedated, restrained and with higher organ failure scores tended to exhibit greater circadian rest–activity misalignment, with three of 34 (9%) patients exhibiting no circadian rhythmicity. Circadian light–dark exposure misalignment was observed as well and was associated with rest–activity misalignment (p = 0.03). Critically ill patients in our MICU experienced profound circadian rest–activity misalignment, with mostly weak or absent rhythms, along with circadian light–dark exposure misalignment. Potentially modifiable factors contributing to rest–activity misalignment (i.e. mechanical ventilation, restraints, low daytime light levels) highlight possible targets for future improvement efforts.