Disturbance of circadian rhythms caused by shift work has adverse effects on insulin resistance. Many previous studies have confirmed that shift work and insulin resistance are related using homeostasis model assessment-insulin resistance, one of the insulin resistance indicators. However, the triglycerides and glucose index (TyG index) has recently been studied as an insulin resistance indicator. The aim of this study is to investigate the association of shift work and TyG index, one of the indirect indicators of insulin resistance, using results of health checkups in one workplace.

Based on medical examination data collected in February 2019, a total of 3,794 subjects from one chemical plant in Korea were selected for this study. Cut-off value of TyG index for predicting development of diabetes mellitus (DM) was 4.69. A multiple logistic regression analysis was performed after adjusting for age, employment period, obesity, abdominal obesity, smoking, drinking, physical activity, hypertension, stroke, heart disease.

As a result of logistic regression analysis, compared to day workers, odds ratio (OR) with a TyG index above cut-off value for predicting development of DM in shift workers was 1.220 after adjusting for age, employment period, obesity, abdominal obesity, smoking, drinking, physical activity, hypertension, stroke, heart disease (Model 1, OR: 1.276; 95% confidence interval [CI]: 1.099–1.482; Model 2, OR: 1.232; 95% CI: 1.055–1.438; Model 3, OR: 1.220, 95% CI: 1.030–1.444).

There was a significant association between shift work and TyG index among male workers in a chemical plant. More research studies on the association between shift work and TyG index are needed in the future.

Circadian rhythm disturbance caused by shift work has adverse effects on the metabolic homeostasis of the liver. Disruption of the metabolic homeostasis of the liver causes fat accumulation in the liver. The aim of this study was to investigate the correlation between shift work and non-alcoholic fatty liver disease (NAFLD) among male workers in the steel manufacturing industry of Korea.

Based on medical examination data collected in June 2020, 2,511 male subjects from one steel manufacturing company in Korea were selected in total. NAFLD was evaluated using abdominal ultrasound, which was performed by two experienced radiologists. The multinomial logistic regression analysis was performed by adjusting for age, physical activity, smoking history, alcohol consumption, body mass index, waist circumference, blood pressure, blood glucose, lipidemia, liver function test, employment duration, and hepatotoxic materials exposure status.

Compared to daytime workers, the odds ratio (OR) of moderate-severe NAFLD in shift workers was 1.449 (95% confidence interval [CI], 1.028–2.043). Compared to daytime workers, the ORs of moderate-severe NAFLD were significantly higher for the group that engaged in total shift work for more than 20 years (OR, 2.285; 95% CI, 1.051–4.970), the group that was not allowed to sleep during night shift work (OR, 1.463; 95% CI, 1.030–2.078), and the group that consumed food during night shift work (OR, 1.580; 95% CI, 1.093–2.284).

There was a correlation between shift work and moderate-severe NAFLD in male steel manufacturing workers. There will be a need for more research related to the correlation of shift work with steatohepatitis and cirrhosis in the future.