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Morning melatonin has limited benefit as a soporific for daytime sleep after night work.

Authors
Smith-MR; Lee-C; Crowley-SJ; Fogg-LF; Eastman-CI
Source
Chronobiol Int 2005 Sep-Oct; 22(5):873-888
NIOSHTIC No.
20029203
Abstract
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. Subjects also ingested either 1.8 mg sustained-release melatonin or placebo before daytime sleep. Although melatonin at this time should delay the circadian clock, this previous study found that it did not increase the magnitude of phase delays. To determine whether melatonin had a soporific effect, we controlled the various magnitudes of phase delay produced by the other study interventions. Melatonin (n=18) and placebo (n=18) groups were formed by matching a melatonin participant with a placebo participant that had a similar baseline and final DLMO (+/-1 h). Sleep log measurements of total sleep time (TST) and actigraphic measurements of sleep latency, TST, and three movement indices for the two groups were examined. 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.
Keywords
Workers; Sleep-deprivation; Sleep-disorders; Shift-work; Shift-workers; Laboratory-testing; Lighting; Circadian-rhythms; Humans; Demographic-characteristics; Sex-factors; Men; Women
CODEN
CHBIE4
Publication Date
20050901
Document Type
Journal Article
Funding Amount
846000
Funding Type
Grant
Fiscal Year
2005
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-003954
Issue of Publication
5
ISSN
0742-0528
Priority Area
Work Environment and Workforce: Organization of Work
Source Name
Chronobiology International
State
IL
Performing Organization
Rush University Medical Center, Chicago, Illinois
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