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Chronobiol Int. 2012 Jun;29(5):619-28. doi: 10.3109/07420528.2012.675257.

Photic resetting in night-shift work: impact on nurses' sleep.

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Centre for Study and Treatment of Circadian Rhythms, Douglas Mental Health University Institute, Department of Psychiatry, McGill University, Montréal, Québec, Canada.


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: ).

[Indexed for MEDLINE]

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