Randomized placebo-controlled field study of the effects of bright light and melatonin in adaptation to night work.
OBJECTIVE
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.
Bjorvatn
Bjørn
B
Department of Public Health and Primary Health Care, University of Bergen, Kalfarveien 31, N-5018 Bergen, Norway. bjorn.bjorvatn@isf.uib.no
Stangenes
Kristine
K
Oyane
Nicolas
N
Forberg
Knut
K
Lowden
Arne
A
Holsten
Fred
F
Akerstedt
Torbjørn
T
D000223:Adaptation, Psychological / Q000187:drug effects*; D000328:Adult; D000704:Analysis of Variance; D002940:Circadian Rhythm; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D008875:Middle Aged; D011930:Reaction Time / Q000187:drug effects; D012890:Sleep / Q000187:drug effects; D020178:Sleep Disorders, Circadian Rhythm / Q000628:therapy*; D011795:Surveys and Questionnaires
D008550:Melatonin