Objective To examine the relationship between night shift work and elevated level of alanine transaminase (e-ALT) of workers, stratified by status of non-alcohol fatty liver.

Methods We established a prospective cohort of night shift workers in Shenzhen, China. All 4740 male workers who had liver function data from the baseline survey of this night shift workers’ cohort were included in the current analysis. We collected information on demographics, lifestyles, and lifetime working schedule from standardized questionnaire. We examined workers’ NAFL status using liver sonography and their serum ALT levels using the automatic biochemical analyzer. Unconditional logistic regression models were used to evaluate odds ratios (ORs) and 95% confidence interval (95% CI).

Results This cohort contained 39.5% night shift workers. Compared with the day workers, night shift workers had higher odds of e-ALT (OR: 1.18; 95% CI 1.00–1.40). Stratified analysis showed that a positive gradient between night shift years and elevated e-ALT was only restricted to the night shift workers without NAFL. No similar trend was observed among those with NAFL.

Conclusions Night shift work is positively associated with the abnormal liver function in workers without NAFL, which indicates that shift work involving circadian disruption is likely to affect abnormal liver function.

[National Natural Science Foundation of China (Project number 81273172 and 81372964), Shelly@cuhk.edu.hk (Lap Ah Tse)]