Nature and Science of Sleep (May 2021)
A Blue-Enriched, Increased Intensity Light Intervention to Improve Alertness and Performance in Rotating Night Shift Workers in an Operational Setting
Abstract
Tracey L Sletten,1 Bhairavi Raman,1 Michelle Magee,1 Sally A Ferguson,2 David J Kennaway,3 Ronald R Grunstein,4,5 Steven W Lockley,6,7 Shantha MW Rajaratnam1,6,7 1Turner Institute for Brain and Mental Health, School of Psychological Sciences, Monash University, Melbourne, Victoria, Australia; 2Central Queensland University, Appleton Institute, Goodwood, SA, Australia; 3Robinson Research Institute, School of Medicine, Discipline of Obstetrics and Gynaecology, University of Adelaide, Adelaide, SA, Australia; 4Woolcock Institute of Medical Research, University of Sydney, Sydney, NSW, Australia; 5Department of Respiratory & Sleep Medicine, Royal Prince Alfred Hospital, Sydney, NSW, Australia; 6Division of Sleep and Circadian Disorders, Departments of Medicine and Neurology, Brigham and Women’s Hospital, Boston, MA, USA; 7Division of Sleep Medicine, Harvard Medical School, Boston, MA, USACorrespondence: Tracey L SlettenTurner Institute for Brain and Mental Health, School of Psychological Sciences, Monash University, Building 2, 270 Ferntree Gully Road, Notting Hill, Victoria, 3168, AustraliaTel + 61 3 990 20734Email [email protected]: This study examined the efficacy of a lighting intervention that increased both light intensity and short-wavelength (blue) light content to improve alertness, performance and mood in night shift workers in a chemical plant.Patients and Methods: During rostered night shifts, 28 workers (46.0± 10.8 years; 27 male) were exposed to two light conditions each for two consecutive nights (∼ 19:00– 07:00 h) in a counterbalanced repeated measures design: traditional-spectrum lighting set at pre-study levels (43 lux, 4000 K) versus higher intensity, blue-enriched lighting (106 lux, 17,000 K), equating to a 4.5-fold increase in melanopic illuminance (24 to 108 melanopic illuminance). Participants completed the Karolinska Sleepiness Scale, subjective mood ratings, and the Psychomotor Vigilance Task (PVT) every 2– 4 hours during the night shift.Results: A significant main effect of time indicated KSS, PVT mean reaction time, number of PVT lapses (reaction times > 500 ms) and subjective tension, misery and depression worsened over the course of the night shift (p< 0.05). Percentage changes in KSS (p< 0.05, partial η2=0.14) and PVT mean reaction time (p< 0.05, partial η2=0.19) and lapses (p< 0.05, partial η2=0.17) in the middle and end of night shift, expressed relative to start of shift, were significantly improved during the lighting intervention compared to the traditional lighting condition. Self-reported mood did not significantly differ between conditions (p> 0.05).Conclusion: Our findings, showing improvements in alertness and performance with exposure to blue-enriched, increased intensity light, provide support for light to be used as a countermeasure for impaired alertness in night shift work settings.Keywords: shift work, circadian photoreception, alertness, vigilance, light, short-wavelength
