# Correlations between clinical insomnia and psychophysiological factors in postoperative patients discharged from the ICU: A cross‐sectional study

## TL;DR

This study finds that insomnia after ICU discharge is linked to fatigue, depression, and stress symptoms, but not to objective sleep measures like N3 sleep.

## Contribution

The study identifies subjective insomnia severity as a key indicator of post-ICU mental and physical health issues.

## Key findings

- Higher insomnia severity scores correlated with increased fatigue, depression, and post-traumatic stress symptoms.
- Reduced N3 sleep was significantly associated with more severe post-traumatic stress symptoms.
- Objective sleep measures were not significantly linked to fatigue or depression.

## Abstract

Post‐intensive care unit (ICU) patients often experience physical or mental dysfunction. This study aims to investigate the relationship between sleep disturbances and mental and physical problems in patients discharged from the ICU to hospital wards, using both subjective and objective sleep measures.

Patients admitted to the ICU for at least 72 h between November 2021 and June 2022 were included in the study. On the seventh day after ICU discharge, we conducted an objective sleep assessment using an electroencephalogram‐based mobile sleep‐monitoring device. Patients self‐administered severity ratings for fatigue, depression, and post‐traumatic stress (PTS) symptoms. Insomnia symptoms were assessed using the insomnia severity index (ISI) before and after ICU admission.

Thirty‐five patients (median age 73) were included in the study. Higher ISI scores at ward were significantly correlated with higher levels of fatigue (r = 0.463, P = 0.005), depression (r = 0.343, P = 0.044), and PTS symptoms (r = 0.477, P = 0.004). Among the objective sleep measures, reduced N3 sleep (r = −0.480, P = 0.004) was significantly correlated with more severe PTS symptoms. However, no statistically significant correlations were found between objective sleep indicators and either fatigue or depression.

The observed reduction in N3 sleep and its association with PTS symptoms in this study might have reflected the physical and psychological stress experienced during intensive care. Subjective insomnia severity, which was related to fatigue, depression, and PTS symptoms in the ward, could be an important intervention target after ICU discharge.