Night shifts significantly reduced cerebral oxygenation, cognitive performance, and increased state anxiety in emergency nurses, with shorter sleep duration during night shifts associated with lower regional cerebral oxygenation in both night shift and rested conditions.
Key Findings
Results
Night shifts caused a significant decline in regional cerebral oxygenation (rSO2) in emergency nurses compared to a rested day shift condition.
rSO2 after night shift was 64.45 ± 6.78 compared to 67.65 ± 6.37 after a full night of rest (p < 0.001)
Cerebral oxygenation was measured using near-infrared spectroscopy (NIRS) during a verbal fluency task targeting prefrontal cortex reactivity
Study used a within-subject crossover design with 67 emergency nurses, with a 14-day washout period between conditions
Assessments were conducted either after completing a night shift or during a day shift following a full night of rest at home, with order randomly assigned
Results
Night shifts significantly reduced cognitive performance as measured by the Verbal Fluency Test (VFT).
VFT scores after night shift were 42.85 ± 11.99 compared to 47.19 ± 11.14 after a full night of rest (p < 0.001)
The VFT was administered concurrently with NIRS to assess prefrontal cortex function during cognitive task performance
The sample consisted of 67 emergency nurses evaluated in a prospective, observational, crossover design
Results
State anxiety was significantly increased in emergency nurses following night shifts compared to the rested condition.
State anxiety scores (STAI) after night shift were 21.37 ± 7.67 compared to 14.63 ± 9.53 after a full night of rest (p < 0.001)
Anxiety was measured using the State Trait Anxiety Inventory (STAI), a validated instrument
Sleep disturbance was also assessed using the Insomnia Severity Index as part of the battery of validated instruments
Results
Shorter sleep duration during night shifts was associated with lower rSO2 mean in both the night shift and rested (NR) conditions.
The association between shorter sleep and lower rSO2 was observed across both measurement conditions (NR and NS)
This suggests a carry-over or chronic effect of reduced sleep on cerebral oxygenation beyond the immediate post-shift period
Sleep duration was self-reported by participants
Results
Nurses who reported longer sleep during night shifts exhibited higher rSO2 but paradoxically poorer cognitive performance, suggesting possible compensatory mechanisms in those with shorter sleep.
Nurses with shorter sleep during night shifts appeared to maintain task performance despite reduced rSO2, suggesting engagement of compensatory cognitive mechanisms
The authors note that longer self-reported sleep 'did not necessarily confer cognitive benefits and may reflect inefficient or overestimated sleep'
This paradoxical finding complicates straightforward interpretation of sleep duration as a protective factor for cognitive performance in this population
Methods
The study employed a prospective, observational, within-subject, crossover design with 67 emergency nurses to control for inter-individual variability.
Each participant was evaluated both after a night shift and during a day shift following a full night of rest at home
The order of assessments was randomly assigned to control for order effects
A 14-day washout period separated the two assessment conditions
Validated instruments used included the State Trait Anxiety Inventory (STAI), Insomnia Severity Index, and NIRS with Verbal Fluency Test (VFT)
What This Means
This research suggests that working night shifts has measurable negative effects on brain function, thinking ability, and emotional state in emergency room nurses. The study compared 67 nurses tested both after a night shift and after a normal night of sleep at home. After night shifts, nurses showed reduced oxygen levels in the prefrontal region of the brain (the area responsible for complex thinking and decision-making), scored lower on a word generation cognitive test, and reported significantly higher anxiety levels. These differences were statistically significant, meaning they were unlikely to be due to chance.
An interesting and somewhat surprising finding was that nurses who reported sleeping longer during their night shifts actually had better brain oxygenation but performed worse on the cognitive test compared to those who slept less. The researchers suggest that nurses who slept less may have activated compensatory mental strategies to keep their performance up despite lower brain oxygen levels, and that longer reported sleep during night shifts may have been inefficient or overestimated by the participants. Additionally, sleeping less during night shifts was associated with lower brain oxygenation not just after the night shift but also when measured after a regular night's sleep at home, hinting at possible longer-term or cumulative effects of night shift sleep disruption on brain health.
This research suggests that night shift work poses real risks to the cognitive functioning and psychological well-being of emergency nurses, which could have implications for patient safety. The authors call for organizational changes such as optimized shift scheduling, structured rest breaks, and programs to support mental health. Simply ensuring that nurses get more sleep during night shifts may not be sufficient if that sleep is of poor quality, pointing to the need for more nuanced approaches to managing the health impacts of shift work in healthcare settings.
Casas-Méndez C, Martín-Parrilla M, Cáceres M, Montanero-Fernández J, López-Jurado C, Durán-Gómez N. (2026). Effects of Night Shifts on Sleep, Cognitive Performance, and Anxiety in Emergency Nurses: An Observational Within-Subject Study.. Journal of nursing management. https://doi.org/10.1155/jonm/1635579