Photic Resetting in Night-Shift Work: Impact on Nurses' Sleep

Abstract

The objective of this study was to quantify daytime sleep in night-shift workers with and without an intervention designed to recover the normal relationship between the endogenous circadian pacemaker and the sleep/wake cycle. Workers of the treatment group received intermittent exposure to full-spectrum bright light during night shifts and wore dark goggles during the morning commute home. All workers maintained stable 8-h daytime sleep/darkness schedules. The authors found that workers of the treatment group had daytime sleep episodes that lasted 7.1 ± .1 h (mean ± SEM) versus 6.6 ± .2 h for workers in the control group (p = .04). The increase in total sleep time co-occurred with a larger proportion of the melatonin secretory episode during daytime sleep in workers of the treatment group. The results of this study showed reestablishment of a phase angle that is comparable to that observed on a day-oriented schedule favors longer daytime sleep episodes in night-shift workers. (Author correspondence: [email protected])

Keywords:

• Bright light
• Melatonin
• Night-Shift, Phase shift adjustment
• Shiftwork
• Sleep

ACKNOWLEDGMENTS

This work was done by the Douglas Mental Health University Institute research team and supported by grants from the Institut de Recherche Robert-Sauvé en Santé et en Sécurité du Travail, the Fonds de Recherche en Santé du Québec, and the Canadian Institutes for Health Research.

The authors are deeply appreciative of the cooperation of the participating night-shift workers and the support of their supervisors. The authors wish to thank the staff and students of the Centre for Study and Treatment of Circadian Rhythms for their contributions to this investigation. The authors also thank Élyse Chevrier for the analysis of sleep episodes; Dr. Sylvie Rhéaume, Dr. Alain Solignac, and Abdelmadjid Azzoug R.N. for medical supervision; Francine Duquette for dietary information; and Véronique Pagé for statistical advices.

Declaration of Interest: D.B.B. is founder/CEO of Alpha Logik Consultants Inc. F.O.J.'s current affiliation is with the Operational and Fatigue Research Division, Institutes for Behavior Resources, Inc., Baltimore, MD, USA. She worked on this project during the course of her graduate studies at the Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute. The authors alone are responsible for the content and writing of the paper.