ObjectiveThe present study was designed to demonstrate the relationships among shift work, hair cortisol concentration (HCC) and sleep disorders.DesignA cross-sectional study.SettingThree petroleum administrations in Karamay city of Xinjiang, China.Participants435 individuals including 164 males and 271 females participated in the research.Outcome measuresInformation on shift work was collected by a self-administered questionnaire. HCC was determined using an automatic radioimmunoassay instrument. Sleep quality was measured on the Pittsburgh Sleep Quality Index scale.ResultsShiftwork was associated with an increased prevalence of sleep disorders compared with the fixed day shift (two shifts: OR 3.11, 95% CI 1.57 to 6.19; three shifts: OR 2.87, 95% CI 1.38 to 5.98; four shifts: OR 2.22, 95% CI 1.17 to 4.18; others: OR 3.88, 95% CI= 1.36 to 11.08). Workers with different shift patterns had higher HCC levels than day workers ((fixed day shift: geometric mean±geometric SD=2.33±1.65; two shifts: 3.76±1.47; three shifts: 3.15±1.64; four shifts: 3.81±1.55; others: 3.60±1.33) ng/g hair, η2=0.174) and high HCC was associated with the higher prevalence of sleep disorders (OR 4.46, 95% CI 2.70 to 7.35). The mediating effect of HCC on the relationship between shift work and sleep disorders was 0.25 (95% CI 0.09 to 0.41).ConclusionWe found that, when compared with the fixed day shift, shiftwork was associated with both the higher HCC, and also with an increased risk of sleep disorders. High HCC was associated with the occurrence of sleep disorders. In addition, HCC had mediating effect in shift work and sleep disorders. Thus, HCC can be considered as an early marker of shiftwork circadian disruption to early detection and management of sleep disorders.

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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.