Sleep and Work Functioning in Nurses Undertaking Inpatient Shifts in a Blue-Depleted Light Environment

Background: Blue-depleted light environments (BDLEs) may in some cases benefit health outcomes for hospital inpatients. However, less is known about the effects on hospital staff. This study aimed to explore the effects of a BDLE compared with a standard hospital light environment (STLE) in a naturalistic setting on nurses’ functioning during shifts and sleep patterns between shifts. Methods: : Twenty-five nurses recruited from St. Olavs Hospital in Trondheim, Norway, completed 14 days of actigraphy recordings and self-reported assessments of sleep (e.g., total sleep time/sleep efficiency) and functioning while at work (e.g., mood, stress levels/caffeine use) in two different light conditions. Additionally, participants were asked to complete several validated scales and questionnaires to assess symptoms on medical conditions, mental health conditions, and side effects associated with the light conditions. Results: : A multilevel fixed-effects regression model showed a within-subject increase in subjective sleepiness (by 17%) during evening shifts in BDLE compared with STLE (p = .034; Cohen’s d = 0.49) and an 0.2 increase in number of caffeinated beverages during nightshifts in STLE compared with BDLE (p = .027; Cohen’s d = 0.37). There were no significant differences neither on subjective or objective sleep measures, nor on self-reported levels of stress or mood across the two conditions. Exploratory between-groups analyses of questionnaire data showed that there were no significant differences except that nurses working in BDLE reported that the lighting was perceived as warmer (p = .009) and more relaxing (p = .023) than nurses working in STLE. Conclusions: : Overall, there was little evidence that the changed light condition had any negative impact on nurses’ sleep and function, despite some indication of increased evening sleepiness in BDLE. We recommend further investigations on this topic before BDLEs are implemented as standard solutions in healthcare institutions and propose specific suggestions for designing future large-scale trials and cohort studies. Trial registration: The study was registered before data collection was completed on the ISRCTN website (ISRCTN21603406).