# Sleep Quality, Circadian Rhythm Stability and Changes in Delirium State in Predicting Mortality Risk in Intensive Care Unit Patients: A Prospective Observational Study

## TL;DR

This study shows that sleep quality and circadian rhythm stability in ICU patients are linked to delirium and higher mortality risk.

## Contribution

The study introduces the use of actigraphy to measure sleep and circadian patterns as predictors of delirium and mortality in ICU patients.

## Key findings

- Prolonged delirium and new-onset delirium were each associated with 45% mortality, significantly higher than the 13.3% in the no-delirium group.
- Lower circadian rhythm stability (r24) was strongly linked to prolonged delirium and higher mortality.
- Higher wake after sleep onset (WASO) was associated with new-onset delirium.

## Abstract

Delirium is a common neuropsychiatric complication in the intensive care unit (ICU), the occurrence of which is closely associated with patient prognoses.

To examine the associations between sleep quality and circadian rhythm stability measured by actigraphy and changes in delirium state in intensive care unit (ICU) patients, as well as their predictive power for mortality risk.

ICUs of a medical centre in Taiwan, from September 1, 2024, to January 31, 2025. A prospective observational study was conducted in adult ICU patients. Wrist‐worn actigraphy was used to monitor total sleep time (TST, h), wake after sleep onset (WASO, h), and circadian rhythm stability (24‐h autocorrelation coefficient, r24) for 72 consecutive hours. Delirium was assessed twice daily for three days using the Confusion Assessment Method for the ICU (CAM‐ICU) and categorized as no delirium, prolonged delirium (lasting ≥ 3 days), or new‐onset delirium (developed after enrollment).

A total of 74 ICU patients were included. Among them, 30 had no delirium, 20 had prolonged delirium, and 24 developed new‐onset delirium. Mortality rates in both the prolonged delirium and new‐onset delirium groups were 45%, significantly higher than in the no‐delirium group (13.3%, p = 0.015). The prolonged delirium group had higher Sequential Organ Failure Assessment (SOFA) scores, longer WASO and lower r24 than the no‐delirium group, with r24 significantly associated with prolonged delirium (OR = 0.001, p = 0.012). The new‐onset delirium group showed higher WASO, which was significantly associated with delirium (OR = 1.04, p = 0.046). Multivariate Cox analysis identified prolonged delirium (HR = 3.92, p = 0.049) and SOFA score (HR = 1.32, p = 0.027) as independent predictors of mortality.

WASO and r24 were closely linked to delirium state changes. Lower r24 was strongly associated with prolonged delirium and higher mortality, while higher WASO was related to new‐onset delirium.

Continuous monitoring of sleep continuity and circadian rhythms in ICU patients is recommended. Incorporating WASO into early delirium risk assessments may facilitate timely interventions, reduce delirium incidence and mortality and improve critical care quality.