Randomized placebo-controlled field study of the effects of bright light and melatonin in adaptation to night work

Jun 19, 2007Scandinavian journal of work, environment & health

Bright light and melatonin effects on adjusting to night work in a controlled field study

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Abstract

Melatonin increased sleep duration by 15-20 minutes per day among night shift workers.

Subjective measures showed that melatonin reduced daytime sleepiness during the day shift.
Bright light exposure resulted in sleep improvements that were intermediate between melatonin and placebo.
Objective measures indicated a minor enhancement of sleep during the night shift with bright light exposure.
Both melatonin and bright light produced modest improvements in sleep and sleepiness in this field study.
The limited effectiveness in this study may be influenced by real-life conditions or suboptimal treatment timing.

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OBJECTIVES: This study evaluated the effects of bright light and melatonin on adaptation to night work on an oil rig in the North Sea.

METHODS: Seventeen persons working a schedule of 2 weeks on a 12-hour shift, with the first week on night shift and the second week on day shift (ie, the swing shift schedule) participated. In a randomized controlled crossover design, the shift workers received a placebo, melatonin (3 mg, 1 hour before bedtime), or bright light (30-minute exposure, individually scheduled) during the first 4 days on the night shift and during the first 4 days on the day shift. Subjective and objective measures of sleepiness (Karolinska Sleepiness Scale and a simple serial reaction-time test) and sleep (diary and actigraphy) were recorded.

RESULTS: Subjective measures indicated that melatonin modestly reduced sleepiness at work during the day shift and increased sleep by 15-20 minutes per day. Bright light gave values in between those of melatonin and the placebo, but with few significant results. According to the objective measures, bright light improved sleep to a minor degree during the night shift. Hardly any side-effects were reported.

CONCLUSIONS: Melatonin and bright light modestly improved sleep and sleepiness in this field study. In well-controlled simulated nightwork studies, both melatonin and bright light are more effective in alleviating sleepiness and sleep problems. The less effect in this field study may be due to competing or conflicting factors present in real life or to an inoptimal timing and duration of the treatments.

Randomized placebo-controlled field study of the effects of bright light and melatonin in adaptation to night work

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