Association between night-shift work and level of melatonin: systematic review and meta-analysis

source extracted confidence: high 2026-04-09
#chronobiology-disorders #circadian-rhythm #humans #melatonin #middle-aged

Association between night-shift work and level of melatonin: systematic review and meta-analysis

Wei et al., 2020 | Sleep Med | Meta Analysis

Citation

Wei Tao, Li Cancan, ... Hou Haifeng. Association between night-shift work and level of melatonin: systematic review and meta-analysis. Sleep Med. 2020-Nov;75:502-509. doi:10.1016/j.sleep.2020.09.018

Abstract

BACKGROUNDS: Night-shift workers are exposed to nocturnal light and are more prone to circadian rhythm disorders. Although night-shift work is thought to be associated with the decrease in melatonin secretion, studies have shown inconsistent results. METHODS: This systematic review and meta-analysis studied the association between night-shift work and melatonin levels. Pubmed and Embase databases were used for literature searching. The pooled standardized mean differences (SMDs) and 95% confidence intervals (CIs) were used to compare the differences between night-shift workers and the controls. RESULTS: Thirty-three studies reported in 25 articles (1845 night-shift workers and 3414 controls, mean age 45.12 years) were included after a systematic literature review. Data of circulating melatonin levels and its metabolites, 6-sulfatoxymelatonin (aMT6s) in urine were collected for meta-analysis. The results showed that the first morning-void aMT6s level in night-shift workers was significantly lower than in day workers (SMD = -0.101, 95% CI = -0.179 to -0.022, P = 0.012). The level of mean 24-h urinary aMT6s was lower in night-shift workers than day workers (SMD: -0.264, 95% CI: -0.473 to -0.056, P = 0.013). Among fixed night-shift workers, the level of circulating melatonin, as well as first morning-void aMT6s was lower than that of day workers. CONCLUSION: Our findings indicate that experience of night-shift work is associated with suppression of melatonin production, especially among fixed night-shift workers.

Key Findings

Thirty-three studies reported in 25 articles (1845 night-shift workers and 3414 controls, mean age 45.12 years) were included after a systematic literature review. Data of circulating melatonin levels and its metabolites, 6-sulfatoxymelatonin (aMT6s) in urine were collected for meta-analysis. The results showed that the first morning-void aMT6s level in night-shift workers was significantly lower than in day workers (SMD = -0.101, 95% CI = -0.179 to -0.022, P = 0.012). The level of mean 24-h uri

Outcomes Measured

  • Requires manual extraction

Population

Field Value
Population See abstract
Sample Size See abstract
Age Range mean age 45.12
Condition See abstract

MeSH Terms

  • Chronobiology Disorders
  • Circadian Rhythm
  • Humans
  • Melatonin
  • Middle Aged
  • Shift Work Schedule
  • Work Schedule Tolerance

Evidence Classification

  • Level: Meta Analysis
  • Publication Types: Journal Article, Meta-Analysis, Research Support, Non-U.S. Gov't, Systematic Review
  • Vertical: melatonin-jet-lag

Provenance

Source extracted via PubMed E-utilities API on 2026-04-09