Subjective and objective sleep assessments correlate only modestly in ICU patients, indicating each method captures unique information, and reliance on a single assessment method may result in incomplete understanding of sleep disruption.
Subjective sleep quality as measured by RCSQ scores declined over the ICU stay from Day 1 to Day 5.
Objective sleep efficiency as measured by Fitbit Sense wearable devices also declined over the ICU stay.
Subjective sleep quality was significantly associated with illness severity, current smoking, surgical admission, mechanical ventilation, and analgesic/sedative use.
Objective sleep quality was associated with a different set of clinical factors than subjective sleep quality, including age, delirium, high-flow oxygen therapy, and analgesic/sedative use.
The correlation between subjective and objective sleep measures was modest in ICU patients.
The study enrolled 355 ICU patients across a multi-centre prospective design yielding 706 paired sleep episodes.
This research suggests that sleep quality in ICU patients worsens over the course of their hospital stay, with both self-reported sleep quality and device-measured sleep efficiency declining over five days. The study tracked 355 critically ill patients across six ICUs in South Korea, having them complete a standard sleep questionnaire each morning while simultaneously wearing a Fitbit smartwatch to objectively measure their sleep. When the two types of measurements were compared, they only weakly agreed with each other, meaning that what patients said about their sleep did not strongly match what the device recorded. The research also found that different clinical factors were linked to different aspects of sleep. Factors like illness severity, mechanical ventilation, and surgical admission were linked to how patients felt about their sleep, while age, delirium, and high-flow oxygen therapy were linked to what the device measured. Interestingly, pain and sedative medications were associated with both types of sleep measures. This suggests that subjective feelings about sleep and the physical, measurable aspects of sleep are partially separate phenomena in the ICU setting. This research suggests that relying on just one way of measuring sleep — either asking patients or using a device — may give an incomplete picture of how well critically ill patients are sleeping. Because the two methods each capture something the other misses, using both together could help nurses and other ICU staff better identify patients who need targeted help with sleep, and tailor care plans accordingly. The findings point to the potential value of wearable sleep-tracking technology as a practical complement to standard patient questionnaires in intensive care settings.
Kang J, Cho H. (2026). Subjective and objective sleep measurements in ICU Patients: A longitudinal analysis of 706 sleep episode pairs.. Intensive & critical care nursing. https://doi.org/10.1016/j.iccn.2026.104380