Effects of melatonin administration on daytime sleep after simulated night shift work - PubMed (original) (raw)

Clinical Trial

Effects of melatonin administration on daytime sleep after simulated night shift work

K M Sharkey et al. J Sleep Res. 2001 Sep.

Abstract

Disturbed sleep and on-the-job sleepiness are widespread problems among night shift workers. The pineal hormone melatonin may prove to be a useful treatment because it has both sleep-promoting and circadian phase-shifting effects. This study was designed to isolate melatonin's sleep-promoting effects, and to determine whether melatonin could improve daytime sleep and thus improve night time alertness and performance during the night shift. The study utilized a placebo-controlled, double-blind, cross-over design. Subjects (n=21, mean age=27.0 +/- 5.0 years) participated in two 6-day laboratory sessions. Each session included one adaptation night, two baseline nights, two consecutive 8-h night shifts followed by 8-h daytime sleep episodes and one recovery night. Subjects took 1.8 mg sustained-release melatonin 0.5 h before the two daytime sleep episodes during one session, and placebo before the daytime sleep episodes during the other session. Sleep was recorded using polysomnography. Sleepiness, performance, and mood during the night shifts were evaluated using the multiple sleep latency test (MSLT) and a computerized neurobehavioral testing battery. Melatonin prevented the decrease in sleep time during daytime sleep relative to baseline, but only on the first day of melatonin administration. Melatonin increased sleep time more in subjects who demonstrated difficulty in sleeping during the day. Melatonin had no effect on alertness on the MSLT, or performance and mood during the night shift. There were no hangover effects from melatonin administration. These findings suggest that although melatonin can help night workers obtain more sleep during the day, they are still likely to face difficulties working at night because of circadian rhythm misalignment. The possibility of tolerance to the sleep-promoting effects of melatonin across more than 1 day needs further investigation.

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Figures

Figure 1

Figure 1

Sample protocol diagram for a participant with baseline sleep scheduled from 00:00 to 08:00 h. Each subject participated in the protocol twice; melatonin was administered during one session and placebo was administered during the other session. B1 = Baseline 1; B2 = Baseline 2; D1 = Day Sleep 1; D2 = Day Sleep 2; R = recovery.

Figure 2

Figure 2

Total sleep times (mean ± SEM) recorded with polysomnography during the melatonin session (●) and placebo session (○). B1 = Baseline 1; B2 = Baseline 2; D1 = Day Sleep 1; D2 = Day Sleep 2; R = Recovery. Melatonin or placebo was administered 0.5 h before sleep on D1 and D2. Time in bed was 8 h. n = 21, *P < 0.05 between melatonin and placebo.

Figure 3

Figure 3

Amount of polysomnographic sleep (mean ± SEM) during the first and second halves of the day sleep episodes (first and last 4 h) during the melatonin session (●) and the placebo session (○). *P < 0.05 between melatonin and placebo.

Figure 4

Figure 4

Average Stanford sleepiness scale ratings (mean ± SEM) from bedtime questionnaires, wake time questionnaires, and test bouts during the night shifts. 1 = ‘feeling active and vital; alert; wide awake’ and 7 = ‘almost in reverie; sleep onset soon; must struggle to remain awake.’ (●) The melatonin session, (○) the placebo session. B = Bed-time ratings; W = Wake time ratings; numbers 1–4 indicate the sequential test bouts during the night shifts. *P < 0.01.

Figure 5

Figure 5

Average sleep latencies (mean ± SEM) from the four MSLT naps administered during the night shifts. M = Melatonin session; P = Placebo session. Filled symbols indicate the melatonin session and open symbols indicate the placebo session. Triangles indicate the first night shift and boxes indicate the second night shift.

Figure 6

Figure 6

Examples of performance test results from the neurobehavioural assessment battery during the night shifts. Filled symbols indicate the melatonin session and open symbols indicate the placebo session. Triangles indicate the first night shift and boxes indicate the second night shift. Top: General activation (GA) scores (mean ± SEM) from the activation–deactivation adjective checklist (ADACL). To complete the ADACL, subjects rated 20 adjectives on whether they described their mood at the time of the test battery. The four possible ratings were ‘definitely feel’, ‘feel slightly’, ‘cannot decide at the moment’ and ‘definitely do not feel.’ The GA subscore is compiled from subjects’ responses to five descriptors (full-of-pep, active, vigorous, energetic, and lively). Bottom: Lapses (mean ± SEM) on the psychomotor vigilance task (PVT). This task measures visual reaction time during a 10-min vigilance task, and any reaction time longer than 0.5 s is considered a lapse. Lapses are plotted as the square root transformation of the number of reaction times >0.5 s.

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References

    1. Akerstedt T. Psychological and psychophysiological effects of shift work. Scand J Work Environ Health. 1990;16 (Suppl 1):67–73. - PubMed
    1. Akerstedt T. Sleepiness as a consequence of shift work. Sleep. 1988;11:17–34. - PubMed
    1. Akerstedt T, Torsvall L, Gillberg M. Sleepiness and shift work: field studies. Sleep. 1982;5:S95–S106. - PubMed
    1. Akerstedt T. Work hours, sleepiness and the underlying mechanisms. J Sleep Res. 1995;4 (Suppl 2):15–22. - PubMed
    1. Akerstedt T. Work schedules and sleep. Experientia. 1984;40:417–422. - PubMed

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