Evening light reduces fatigue and errors during night shifts: A randomised controlled trial

Abstract

Objective: Shift work causes circadian rhythms to misalign with the demands of the environment, which has been associated with sleep difficulties and cognitive impairments. Although bright light exposure during night shifts can improve circadian alignment, its implementation is often infeasible. Here, we tested whether light exposure in the evening, before the night shift, could improve fatigue, work performance, mood, and sleep. Methods: Fifty-seven healthy nurses who worked full-time rapidly rotating shift schedules completed the study. In a mixed-design randomised controlled trial, participants completed a baseline observation period before following one of two interventions. The experimental intervention aimed to improve circadian alignment using evening light exposure and morning light avoidance; the control intervention aimed to improve alertness and reduce sleep disturbances by modifying diet. Every morning and evening for 30 days, participants completed measures of fatigue, work-related errors, sleepiness, mood, sleep duration, and sleep quality. Results: Compared to the baseline observation period, the experimental intervention reduced errors by 67% while the control intervention reduced them by only 5%. This reduction was partially mediated by fatigue; experimental participants reported less fatigue on work days than control participants (d = 0.25 [0.12, 0.38]). The experimental group also showed a small improvement in mood. Both groups showed reductions in fatigue (d = .29 [.20, .35]) and sleepiness (d = 0.21 [0.13, 0.29]) as well as a small increase in sleep duration. Conclusion: Interventions based on evening light may thus be a feasible and effective strategy to reduce fatigue and errors in night shift workers.

Interventions to improve the sleep of nurses: A systematic review

“…Table 2 summarizes the biases and qualities of the RCTs. Overall, 7 out of 22 RCTs were graded as low risk of bias (good quality) (Baradari et al, 2018; Chang et al, 2017; Cyr et al, 2023; Hsu et al, 2021; Mousavi et al, 2020; Niu et al, 2021; Zhang et al, 2020), and the rest were graded as high risk of bias. Dropout rates of the RCTs were moderate, with 10 RCTs reporting dropout rates of <10%, and 12 RCTs reporting dropout rates from 12.5% to 77% (Aarts et al, 2020; Bjorvatn et al, 2021; Booker et al, 2022; Carter et al, 2013; Dahlgren et al, 2022; Fang & Li, 2015; Hoshi et al, 2022; Lee et al, 2014; Morimoto et al, 2016; Omeogu et al, 2020; Scott et al, 2010b; Zhang et al, 2020).…”

“…All of the studies except three (Booker et al, 2022; Cyr et al, 2023; Mousavi et al, 2020) used sleep as a primary outcome. Although these three studies did not measure sleep as a primary outcome, because the intervention in each of these studies addressed fatigue/sleep, the study team deemed them relevant and included them in this review.…”