Sadeghniiat-Haghighi K1,2, Bahrami H1,2, Aminian O1,2, Meysami A3, Khajeh-Mehrizi A1.

Abstract
BACKGROUND:
Disturbed sleep is common in shift work. It is hypothesized that administration of exogenous melatonin could reduce the sleep latency and improve the sleep quality.

OBJECTIVE:
To evaluate the efficacy of 3 mg melatonin taken 30 min before night time sleep on shift workers with difficulty falling asleep.

METHODS:
Pittsburgh Sleep Quality Index (PSQI) and Insomnia Severity Index (ISI) were applied to find out shift workers with difficulty falling asleep. A randomized, double-blind, placebo-controlled crossover study with periods of 3 night and washouts of 2 weeks comparing melatonin with placebo was performed. Night time sleep parameters obtained from somnowatch including total sleep time (TST), sleep onset latency (SOL), sleep efficiency (SE) and wakening after sleep onset (WASO) were analyzed.

RESULTS:
Among 295 workers, 103 had difficulty falling asleep. Finally, from 50 randomly selected workers with difficulty falling asleep, 39 workers completed the study. Melatonin treatment significantly increased SE and decreased SOL in comparison with baseline and taking placebo. SE was increased from 82.1% at baseline to 85.5% after melatonin therapy. Also SOL was decreased from 0.27 h at baseline to 0.20 h after melatonin therapy. Effects of Melatonin administration on TST and WASO were not significant.

CONCLUSIONS:
This study showed that melatonin therapy in shift workers with difficulty falling asleep significantly improved the sleep onset latency and sleep efficiency.

KEYWORDS:
Circadian rhythm; sleep efficiency; sleep onset latency; somnowatch