No abstract

To examine the relationships between different shift patterns and Type 2 diabetes mellitus (T2DM) risk, and determine whether physical exercise reduced the incidence of T2DM in shift workers in the oil industry. Baseline data were collected from participants in May 2013 who were then followed for 4 years in a prospective cohort study. The cohort initially consisted of 3,002 workers and ultimately included 2,827 people. Baseline and follow-up questionnaires were sent to participants every 2 years (in May 2015 and May 2017) to update medical and lifestyle information during the follow-up period. The risk of T2DM among two shift workers [relative risk (RR) = 3.442, 95% CI: 1.904–6.799)], three shift workers (RR = 2.534, 95% CI: 1.484–4.571), and four shift workers (RR = 4.230, 95% CI: 2.680–7.518) was higher than that among day workers. An increasing trend was observed with respect to T2DM risk, with the lowest risk in three shift workers, moderate risk in two shift workers, and highest risk in four shift workers. In the interactive analysis between shift work and physical exercise, taking part in mild physical exercise increased the risk of T2DM for workers. Four shift workers who took part in mild physical exercise had an increased risk of T2DM. The relative excess risk due to interaction (RERI) was 33.769 (0.398–67.140). The attributable proportion due to interaction [API (%)] was 0.704 (0.529–0.880). The synergy index (SI) was 3.563 (1.900–6.683). Shift work is significantly correlated with increased incidence of T2DM. Risk of T2DM is lowest risk in three shift workers, moderate in two shift workers, and highest in four shift workers. Shift workers who participated in moderate and severe physical exercise had reduced risk of developing T2DM.

Background Currently, cardiovascular disease is the leading cause of death, and dyslipidaemia is an independent and modifiable major risk factor. Previous studies on shift work with dyslipidaemia and hair cortisol concentration (HCC) have yielded conflicting results. The aim of this study was to clarify the association between shift work, dyslipidaemia, and HCC. We further explored the mediating effect of HCC. Methods In this cohort study, baseline data were collected from participants in May 2013. The cohort included 2170 participants- 1348 shift workers and 822 non-shift workers- who were followed up for 6 years with four questionnaire surveys from July 2014, October 2015, and May to December 2019. Hair samples were collected from 340 participants during the baseline period for HCC testing with an automated radioimmunoassay. Dyslipidaemia was defined using the National Cholesterol Education Program Adult Treatment Panel III diagnostic criteria. Results Shift workers had a higher risk of dyslipidaemia than workers on the fixed day shift (two-shift RR = 1.408, 95% CI: 1.102–1.798; three-shift RR = 1.478, 95% CI: 1.134–1.926; four-shift RR = 1.589, 95% CI: 1.253–2.015). Additionally, shift workers had higher HCC levels than fixed day shift workers, with geometric mean concentration (GMC) ± geometric standard difference (GSD) = 2.625 ± 2.012 ng/g, two-shift GMC ± GSD = 3.487 ± 1.930 ng/g, three-shift GMC ± GSD = 2.994 ± 1.813 ng/g, and four-shift GMC ± GSD = 3.143 ± 1.720 ng/g. High HCC was associated with a high incidence of dyslipidaemia. After controlling for confounding factors, this study showed that HCC played a role in mediating dyslipidaemia in shift workers and accounted for 16.24% of the effect. Conclusions Shift work was linked to increased risk of dyslipidaemia compared with fixed day shift work. Higher HCC was associated with a higher prevalence of dyslipidaemia. HCC had a significant mediating effect on dyslipidaemia in shift workers.