Research Article|Articles in Press

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

Published:April 18, 2023DOI:



      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.


      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Sleep Health: Journal of the National Sleep Foundation
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Härmä M
        • Karhula K
        • Puttonen S
        • et al.
        Shift work with and without night work as a risk factor for fatigue and changes in sleep length: a cohort study with linkage to records on daily working hours.
        J Sleep Res. 2018; 28e12658
        • James SM
        • Honn KA
        • Gaddameedhi S
        • Dongen HPAV
        Shift work: disrupted circadian rhythms and sleep — implications for health and well-being.
        Curr Sleep Med Rep. 2017; 3: 104-112
        • Killgore WDS
        Effects of sleep deprivation on cognition.
        Progress in Brain Research. Elsevier, 2010: 105-129
        • Watling J
        • Pawlik B
        • Scott K
        • Booth S
        • Short MA
        Sleep loss and affective functioning: more than just mood.
        Behav Sleep Med. 2016; 15: 394-409
        • Boivin DB
        • Boudreau P
        • James FO
        • Kin NMKNY
        Photic resetting in night-shift work: impact on nurses’ sleep.
        Chronobiol Int. 2012; 29: 619-628
        • Lowden A
        • Öztürk G
        • Reynolds A
        • Bjorvatn B
        Working time society consensus statements: evidence based interventions using light to improve circadian adaptation to working hours.
        Ind Health. 2019; 57: 213-227
        • Boivin DB
        • James FO
        Circadian adaptation to night-shift work by judicious light and darkness exposure.
        J Biol Rhythm. 2002; 17: 556-567
        • Eastman CI
        • Liu L
        • Fogg LF
        Circadian rhythm adaptation to simulated night shift work: effect of nocturnal bright-light duration.
        Sleep. 1995; 18: 399-407
        • Smith MR
        • Fogg LF
        • Eastman CI
        Practical interventions to promote circadian adaptation to permanent night shift work: study 4.
        J Biol Rhythm. 2009; 24: 161-172
        • Smith MR
        • Eastman CI
        Shift work: health, performance and safety problems, traditional countermeasures, and innovative management strategies to reduce circadian misalignment.
        Nat Sci Sleep. 2012; 2012 (Published online September): 111-132
        • Crowley SJ
        • Lee C
        • Tseng CY
        • Fogg LF
        • Eastman CI
        Complete or partial circadian re-entrainment improves performance, alertness, and mood during night-shift work.
        Sleep. 2004; 27: 1077-1087
        • Huang L-B
        • Tsai M-C
        • Chen C-Y
        • Hsu S-C
        The effectiveness of light/dark exposure to treat insomnia in female nurses undertaking shift work during the evening/night shift.
        J Clin Sleep Med. 2013; 9: 641-646
        • Hansen J
        • Stevens RG
        Case-control study of shift-work and breast cancer risk in Danish nurses: impact of shift systems.
        Eur J Cancer. 2012; 48: 1722-1729
        • Russart KLG
        • Nelson RJ
        Light at night as an environmental endocrine disruptor.
        Physiol Behav. 2018; 190: 82-89
        • Rybnikova NA
        • Haim A
        • Portnov BA
        Does artificial light-at-night exposure contribute to the worldwide obesity pandemic?.
        Int J Obes. 2016; 40: 815-823
        • Mason IC
        • Grimaldi D
        • Reid KJ
        • et al.
        Light exposure during sleep impairs cardiometabolic function.
        Proc Natl Acad Sci. 2022; 119e2113290119
        • Min J-y
        • Min K-b
        Outdoor light at night and the prevalence of depressive symptoms and suicidal behaviors: a cross-sectional study in a nationally representative sample of Korean adults.
        J Affect Disord. 2018; 227: 199-205
        • Opperhuizen A-L
        • Stenvers DJ
        • Jansen RD
        • Foppen E
        • Fliers E
        • Kalsbeek A
        Light at night acutely impairs glucose tolerance in a time-, intensity- and wavelength-dependent manner in rats.
        Diabetologia. 2017; 60: 1333-1343
        • Blask DE
        • Brainard GC
        • Dauchy RT
        • et al.
        Melatonin-depleted blood from premenopausal women exposed to light at night stimulates growth of human breast cancer xenografts in nude rats.
        Cancer Res. 2005; 65: 11174-11184
        • Cyr M
        • Artenie DZ
        • Bikaii AA
        • Borsook D
        • Olson JA
        The effect of evening light on circadian-related outcomes: a systematic review.
        Sleep Med Rev. 2022; 64101660
        • Olson JA
        • Artenie DZ
        • Cyr M
        • Raz A
        • Lee V
        Developing a light-based intervention to reduce fatigue and improve sleep in rapidly rotating shift workers.
        Chronobiol Int. 2019; 37: 573-591
        • Sallinen M
        • Kecklund G
        Shift work, sleep, and sleepiness—differences between shift schedules and systems.
        Scand J Work Environ Health. 2010; 36 (Published online): 121-133
        • Dall’Ora C
        • Ball J
        • Recio-Saucedo A
        • Griffiths P
        Characteristics of shift work and their impact on employee performance and wellbeing: a literature review.
        Int J Nurs Stud. 2016; 57: 12-27
        • Buysse DJ
        • Reynolds III, CF
        • Monk TH
        • Berman SR
        • Kupfer DJ
        The Pittsburgh sleep quality index: a new instrument for psychiatric practice and research.
        Psychiatry Res. 1989; 28: 193-213
        • Adan A
        • Almirall H
        Horne & Östberg morningness-eveningness questionnaire: a reduced scale.
        Personal Individ Differ. 1991; 12: 241-253
        • Smets E
        • Garssen B
        • de Bonke B
        • De Haes J
        The Multidimensional Fatigue Inventory (MFI): psychometric qualities of an instrument to assess fatigue.
        J Psychosom Res. 1995; 39: 315-325
        • Cohen S
        • Kamarck T
        • Mermelstein R
        A global measure of perceived stress.
        J Health Soc Behav. 1983; 24: 385-396
        • Hart SG
        • Staveland LE
        Development of NASA-TLX (task load index): Results of empirical and theoretical research.
        Adv Psychol. 1988; : 139-183
        • Gupta CC
        • Centofanti S
        • Dorrian J
        • et al.
        Altering meal timing to improve cognitive performance during simulated night shifts.
        Chronobiol Int. 2019; 36: 1691-1713
        • Uçar C
        • Özgöçer T
        • Yıldız S
        Effects of late-night eating of easily-or slowly-digestible meals on sleep, hypothalamo-pituitary-adrenal axis, and autonomic nervous system in healthy young males.
        Stress Health. 2021; 37: 640-649
        • Grant CL
        • Dorrian J
        • Coates AM
        • et al.
        The impact of meal timing on performance, sleepiness, gastric upset, and hunger during simulated night shift.
        Ind Health. 2017; 55: 423-436
        • Grant CL
        • Coates AM
        • Dorrian J
        • et al.
        Timing of food intake during simulated night shift impacts glucose metabolism: a controlled study.
        Chronobiol Int. 2017; 34: 1003-1013
        • Christodoulou C
        • Schneider S
        • Junghaenel DU
        • Broderick JE
        • Stone AA
        Measuring daily fatigue using a brief scale adapted from the patient-reported outcomes measurement information system (PROMIS).
        Qual Life Res. 2013; 23: 1245-1253
        • Scott LD
        • Rogers AE
        • Hwang WT
        • Zhang Y
        Effects of critical care nurses' work hours on vigilance and patients’ safety.
        Am J Crit Care. 2006; 15: 30-37
        • Dorrian J
        • Lamond N
        • van den Heuvel C
        • Pincombe J
        • Rogers AE
        • Dawson D
        A pilot study of the safety implications of Australian nurses’ sleep and work hours.
        Chronobiol Int. 2006; 23: 1149-1163
        • Åkerstedt T
        • Gillberg M
        Subjective and objective sleepiness in the active individual.
        Int J Neurosci. 1990; 52: 29-37
        • Curcio G
        • Casagrande M
        • Bertini M
        Sleepiness: evaluating and quantifying methods.
        Int J Psychophysiol. 2001; 41: 251-263
        • Cappelleri JC
        • Bushmakin AG
        • McDermott AM
        • Sadosky AB
        • Petrie CD
        • Martin S
        Psychometric properties of a single-item scale to assess sleep quality among individuals with fibromyalgia.
        Health Qual Life Outcomes. 2009; 7: 54
        • Thompson ER
        Development and validation of an internationally reliable short-form of the Positive and Negative Affect Schedule(PANAS).
        J Cross-Cult Psychol. 2007; 38: 227-242
        • Tingley D
        • Yamamoto T
        • Hirose K
        • Keele L
        • Imai K
        Mediation: R package for causal mediation analysis.
        J Stat Softw. 2014; 59: 1-38
        • Landrigan CP
        • Rothschild JM
        • Cronin JW
        • et al.
        Effect of reducing interns’ work hours on serious medical errors in intensive care units.
        N Engl J Med. 2004; 351: 1838-1848
        • Kretschmer V
        • Schmidt K-H
        • Griefahn B
        Bright light effects on working memory, sustained attention and concentration of elderly nightshift workers.
        Light Res Technol. 2011; 44: 316-333
        • Gillberg M
        • Kecklund G
        • Axelsson J
        • Åkerstedt T.
        The effects of a short daytime nap after restricted night sleep.
        Sleep. 1996; 19: 570-575
        • Åkerstedt T
        • Anund A
        • Axelsson J
        • Kecklund G
        Subjective sleepiness is a sensitive indicator of insufficient sleep and impaired waking function.
        J Sleep Res. 2014; 23: 242-254
        • Nahra TA
        • Reiter KL
        • Hirth RA
        • Shermer JE
        • Wheeler JRC
        Cost-effectiveness of hospital pay-for-performance incentives.
        Med Care Res Rev. 2006; 63: 49S-72S
      1. O’Brien-Pallas L, TomblinMurphy G, Shamian J. Final report: Understanding the costs and outcomes of nurses’ turnover in Canadian hospitals. University of Toronto Nursing Health Services Research Unit: Toronto, ON, Canada. Published online. 2008.

        • Ritonja J
        • Aronson KJ
        • Matthews RW
        • Boivin DB
        • Kantermann T
        Working Time Society consensus statements: individual differences in shift work tolerance and recommendations for research and practice.
        Ind Health. 2019; 57: 201-212
        • Olson JA
        • Sandra DA
        • Chmoulevitch D
        • Raz A
        • Veissière SPL
        A nudge-based intervention to reduce problematic smartphone use: randomised controlled trial.
        Int J Ment Health Addict. 2022; (Published online May) (Published online May)
        • Münch M
        • Wirz-Justice A
        • Brown SA
        • et al.
        The role of daylight for humans: gaps in current knowledge.
        Clocks Sleep. 2020; 2: 61-85
        • O’Neil AC.
        Physician reporting compared with medical-record review to identify adverse medical events.
        Ann Int Med. 1993; 119: 370