Comparison of Melatonin Levels, Sleep Quality and Alertness between Nurses Working Night Shift and Day Shift

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Preeyaporn Plaimee
Ratklaow Mititraporn
Warangphat Nuangjumnong
Nutjaree Pratheepawanit Johns
Jeffrey Johns


Background and objective: Exposure to artificial light at night, particularly in night shift workers, leads to suppression of natural nocturnal melatonin production. Poorer sleep quality from shiftwork results in increased accident rates during the work, but there is limited data on sleep quality and melatonin production. This study examined the association between melatonin levels, sleep quality and alertness comparing between nurses working night shift and day shift.

Methods: The study was a cross-sectional design. Volunteer nurses working night shift (n = 30) and day shift (n = 29) during the past five years were recruited. Overnight urine samples were collected and assayed for 6-sulphatoxymelatonin (aMT6s), a melatonin metabolite, by enzyme-linked immunosorbent assay (ELISA). Sleep quality using the validated Thai Pittsburgh Sleep Quality Index (T_PSQI), and alertness using the Thai Karolinska Sleepiness Scale (T_KSS) were evaluated. Statistical analysis was performed using Mann-Whitney U-Test and Spearman’s rho-correlation.

Results: The average level of creatinine-adjusted aMT6s in night shift nurses was lower, but not statistically significant, than that of day shift nurses (29.6 ± 32.5 vs. 32.8 ± 58.8 ng/mg Cr; p = 0.439). The night shift nurses also reported poorer sleep quality (T_PSQI were 7.5 ± 5.0 vs. 5.0 ± 2.8; p = 0.001) and less alertness both before (T_KSS were 4.0 ± 6.0 vs. 3.0 ± 2.0; p = 0.006) and during (T_KSS were 6.0 ± 3.0 vs. 3.0 ± 1.8; p = < 0.001) working. There was no correlation between creatinine-adjusted aMT6s and sleep quality nor alertness.

Conclusion: The findings showed poorer sleep quality in nurses working night shift without a significant difference of melatonin levels.

Keywords : 6-sulphatoxymelatonin, shift work, sleep quality, alertness, nurses


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Plaimee P, Mititraporn R, Nuangjumnong W, Johns NP, Johns J. Comparison of Melatonin Levels, Sleep Quality and Alertness between Nurses Working Night Shift and Day Shift. SRIMEDJ [Internet]. 2013 Aug. 23 [cited 2022 Aug. 17];27(4):393-400. Available from:
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