Rotating night shift work, sleep duration and elevated gamma-glutamyl transpeptidase among steelworkers: cross-sectional analyses from a Chinese occupational cohort

OBJECTIVES: This study aimed to evaluate the separate and combined effects of rotating night shift work and lifestyle factors with elevated gamma-glutamyl transpeptidase (GGT) among steelworkers. DESIGN, SETTING AND PARTICIPANTS: This cross-sectional study used the baseline information from a Chinese occupational cohort. The in-service workers of the production department of Tangsteel Company who participated in the occupational health examination in Tangshan from February to June 2017 were selected as the research objects. MAIN OUTCOME MEASURES: The separate and combined effects of rotating night shift work and lifestyle factors with elevated GGT among steelworkers. RESULTS: The information of 7031 subjects from the production department of Tangsteel Company was analysed. Results showed that the current shift workers and the workers with the duration of night shifts>19 years, the cumulative number of night shifts>1774 nights, the average frequency of night shifts≤7 nights/month and the average frequency of night shifts>7 nights/month had elevated odds of elevated GGT, compared with those who never worked night shifts, and ORs, (95% CIs) were 1.39, (1.10 to 1.75), 1.46, (1.15 to 1.86), 1.46, (1.15 to 1.85), 1.34, (1.04 to 1.73) and 1.37, (1.09 to 1.74) after adjustment for potential confounders. The independent effect of shorter sleep duration (<7 hours/day) on elevated GGT was not statistically significant. Among workers who had shorter sleep duration, the association between rotating night shift work and elevated GGT was statistically significant, but no associations were found among workers with the sleep duration of ≥7 hours/day. In addition, other lifestyle factors affected the association between rotating night shift work and elevated GGT. CONCLUSIONS: Rotating night shift work is associated with elevated GGT among steelworkers. In particular, the effect of rotating night shift work on elevated GGT was affected by sleep duration and other lifestyle factors.