An evening light intervention reduces fatigue and errors during night shifts: A randomized controlled trial.

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. 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. 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. Interventions based on evening light may be a feasible and effective strategy to reduce fatigue and errors in night-shift workers.

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Copyright © 2023 National Sleep Foundation. Published by Elsevier Inc. All rights reserved.

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Funding This research was supported by Mitacs (Accelerate award IT16334) and the Canada First Research Excellence Fund, awarded to the Healthy Brains for Healthy Lives initiative (3c-KM-32) at McGill University. MC acknowledges funding from le Fonds de recherche du Québec — Santé (FRQS) and DA acknowledges funding from the Canadian Institutes for Health Research. JO acknowledges funding from the Social Sciences and Humanities Research Council of Canada and FRQS.