All participating nurses were classified as poor sleepers according to the PSQI questionnaire, but objective smartwatch measurements revealed that rotating shift work is associated with significantly poorer sleep quality compared to day-shift-only work.
Key Findings
Results
All 140 nurses were classified as poor sleepers according to the Pittsburgh Sleep Quality Index (PSQI > 5), regardless of shift type.
Total sample size was 140 nurses participating in a prospective, observational, cross-sectional study conducted in Croatia in 2025.
PSQI scores greater than 5 classify individuals as poor sleepers, and all participants exceeded this threshold.
No significant difference in PSQI classification was found between nurses working day shifts only and those working rotating shifts.
Despite this, most nurses subjectively rated their own sleep as 'good' or 'very good', indicating a disconnect between self-perception and validated questionnaire results.
Results
Nurses working only day shifts had significantly higher objective sleep scores than those working rotating shifts as measured by FitBit Charge 3 smartwatch.
Day-shift nurses had a median sleep score of 77 (IQR 75–80) compared to 73 (IQR 68–76) for rotating shift nurses (p < 0.001).
Sleep was monitored objectively over an eight-day period using the FitBit Charge 3 smartwatch.
The difference in sleep scores was statistically significant at p < 0.001.
Results
Nurses working only day shifts had significantly longer total sleep duration compared to those working rotating shifts.
Day-shift nurses had a median total sleep duration of 6.4 hours (IQR 6.3–7.1 h) versus 5.5 hours (IQR 5.2–6.2 h) for rotating shift nurses (p < 0.001).
The difference represents approximately 54 minutes less sleep per night for rotating shift workers.
This finding was based on objective smartwatch monitoring over an eight-day period.
Results
Nurses working only day shifts had longer durations of all sleep stages compared to those working rotating shifts.
Objective smartwatch data showed that rotating shift work was associated with reduced duration across all sleep stages, not just total sleep time.
This was measured using the FitBit Charge 3 smartwatch over an eight-day monitoring period.
Differences were statistically significant as part of the broader pattern of poorer sleep quality in rotating shift workers.
Results
There was a notable discrepancy between nurses' subjective self-assessment of sleep quality and objective or validated questionnaire-based measurements.
Most nurses rated their sleep as 'good' or 'very good' in subjective self-report.
However, all participants were classified as poor sleepers by the validated PSQI instrument (score > 5).
Objective smartwatch measurements further confirmed poorer sleep quality, particularly for rotating shift workers.
This discrepancy suggests nurses may underestimate or be unaware of the degree to which their sleep is impaired.
Methods
The study design combined both subjective (PSQI questionnaire) and objective (FitBit Charge 3 smartwatch) measures of sleep quality over an eight-day monitoring period.
The Pittsburgh Sleep Quality Index (PSQI) was used as the validated subjective sleep assessment tool.
The FitBit Charge 3 smartwatch provided continuous objective sleep monitoring over eight days.
The study was prospective, observational, and cross-sectional, conducted in Croatia in 2025.
A total of 140 nurses participated, with comparisons made between day-shift-only and rotating shift workers.
What This Means
This research suggests that shift work — particularly rotating schedules that cycle nurses through day, evening, and night shifts — significantly harms sleep quality compared to working only day shifts. The study, conducted in Croatia in 2025, followed 140 nurses and used both a standard sleep questionnaire (the Pittsburgh Sleep Quality Index) and a FitBit smartwatch worn for eight days to measure sleep. Nurses on rotating shifts slept about 54 minutes less per night on average and scored lower on objective sleep quality measures than nurses working only during the day.
One of the more striking findings is the gap between how nurses perceived their own sleep and what the measurements actually showed. Most nurses reported that they slept well, yet according to the validated PSQI questionnaire, every single participant — regardless of shift type — was classified as a poor sleeper. This suggests that nurses may have adapted to or normalized their disrupted sleep, making it harder for them to recognize the extent of the problem on their own.
This research matters because poor sleep in healthcare workers can affect not just their personal health and wellbeing, but potentially patient safety and care quality as well. The findings highlight that self-reported sleep quality alone may be insufficient to detect sleep problems in shift workers, and that more objective tools may be needed to fully understand and address this occupational health issue.
Dujmić &, Mikšić &, Barać I, Samardžić J, Maršić L, Samardžić P, et al.. (2026). Sleep Quality in Shift-Working Nurses: Subjective and Objective Evaluation.. International journal of environmental research and public health. https://doi.org/10.3390/ijerph23010064