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 randomized controlled trial, participants completed a
baseline observation period before following 1 of 2 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 [0.10, 0.38]). The experimental group also showed a small improvement in mood.
Both groups showed reductions in fatigue (d = 0.29 [0.20, 0.36]) and sleepiness (d = 0.21 [0.12, 0.28]) as well as a small increase in sleep duration.
Conclusions
Interventions based on evening light may be a feasible and effective strategy to reduce
fatigue and errors in night-shift workers.
Keywords
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Article info
Publication history
Published online: April 18, 2023
Accepted:
February 17,
2023
Received in revised form:
February 16,
2023
Received:
October 12,
2022
Publication stage
In Press Corrected ProofIdentification
Copyright
© 2023 National Sleep Foundation. Published by Elsevier Inc. All rights reserved.
