Chronobiology international
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Controlled Clinical Trial
Morning melatonin has limited benefit as a soporific for daytime sleep after night work.
Exogenous melatonin administration in humans is known to exert both chronobiotic (phase shifting) and soporific effects. In a previous study in our lab, young, healthy, subjects worked five consecutive simulated night shifts (23:00 to 07:00 h) and slept during the day (08:30 to 15:30 h). Large phase delays of various magnitudes were produced by the study interventions, which included bright light exposure during the night shifts, as assessed by the dim light melatonin onset (DLMO) before (baseline) and after (final) the five night shifts. ⋯ Although melatonin was associated with small improvements in sleep quality and quantity, the differences were not statistically significant by analysis of variance. However, binomial analysis indicated that melatonin participants were more likely to sleep better than their placebo counterparts on some days with some measures. It was concluded that, the soporific effect of melatonin is small when administered prior to 7 h daytime sleep periods following night shift work.
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Case Reports
Working under daylight intensity lamp: an occupational risk for developing circadian rhythm sleep disorder?
A 47-yr-old male was admitted to the Institute for Fatigue and Sleep Medicine complaining of severe fatigue and daytime sleepiness. His medical history included diagnosis of depression and chronic fatigue syndrome. Antidepressant drugs failed to improve his condition. ⋯ In addition, the patient reported profound improvement in maintaining wakefulness during the day. This case study shows that chronic exposure to bright light at the wrong biological time, during the nighttime, may have serious effects on the circadian sleep-wake patterns and circadian time structure. Therefore, night bright light exposure must be considered to be a risk factor of previously unrecognized occupational diseases of altered circadian time structure manifested as irregularity of the 24 h sleep-wake cycle and melancholy.