The direction of shift-work rotation impacts metabolic risk independent of chronotype and social jetlag--an exploratory pilot study.

The aim of this pilot study was to explore the risk of metabolic abnormalities in steel workers employed in different shift-work rotations. Male workers in a steel factory [16 employed in a fast clockwise rotation (CW), 18 in slow counterclockwise rotation (CC), 9 day workers (DW); mean age 43.3 ± SD 6.8 years] with at least 5 years experience in their current work schedule participated. All workers provided fasting blood samples between 06:00 and 08:00 h for plasma glucose, insulin, apo-lipoproteins A and B (ApoA, ApoB), high- and low-density lipoproteins (HDL and LDL), total cholesterol (tCH), triglycerides (TG), minimally oxidized (mox) LDL, C-reactive protein (CRP), interleukin-8 (IL-8) and serum 25-hydroxyvitamin D (25(OH)D). HOMA index (homeostatic model assessment) was calculated to evaluate insulin resistance, beta cell function and risk of diabetes. Information on demographics, health, stimulants, sleep, social and work life, chronotype (phase of entrainment) and social jetlag (difference between mid-sleep on workdays and free days) as a surrogate for circadian disruption was collected by questionnaire. Neither chronotype nor social jetlag was associated with any of the metabolic risk blood markers. There were no significant differences in 25(OH)D, ApoA, ApoB, CRP, HDL, IL-8, insulin, LDL, mox-LDL, mox-LDL/ApoB ratio, tCH and TG levels between the three work groups. Although we did observe absolute differences in some of these markers, the small sample size of our study population might prevent these differences being statistically significant. Fasting glucose and HOMA index were significantly lower in CW compared to DW and CC, indicating lower metabolic risk. Reasons for the lower fasting glucose and HOMA index in CW workers remains to be clarified. Future studies of workers in different shift rotations are warranted to understand better the differential effects of shift-work on individual workers and their health indices.

Atherosclerotic risk and social jetlag in rotating shift-workers: first evidence from a pilot study.

OBJECTIVE: The aim of this study was to identify atherosclerotic risk using pulse wave velocity (PWV) in steel workers employed in different shift-work rotations, and to elucidate its relationship to social jetlag and shift schedule details. PARTICIPANTS: Male workers in a steel factory (n=77, 32 fast clockwise (CW), 30 slow counterclockwise (CC), 15 day workers (DW); mean age 42 ± SD 7.6 yrs) with at least 5 years of experience in their current work schedule participated. METHODS: All workers completed questionnaires on demographics, health, psychotropic agents, sleep, social and work life, social jetlag (difference between mid-sleep time on workdays and days off used as a marker of circadian disruption) and chronotype (mid-sleep time on free days corrected for sleep deficit on workdays). In 63 workers we measured PWV, blood pressure (BP), heart rate (HR) between 08:00 and 12:30 h in controlled posture conditions (no caffeine/smoking/exercise). RESULTS: There was no significant difference in PWV (covariates: age, BP) between the different shift-rotations (CW, CC and DW). In all workers combined, HR and social jetlag were significantly positively correlated. Demographic variables did not differ between shift-workers and day workers; shift-workers (CW, CC) reported significantly more stomach upsets, digestion problems, weight fluctuations, and social jetlag. The CW and CC workers did not differ in ratings of how shift-work affected sleep, social and work life. CONCLUSIONS: PWV was not different between the two shift-rotations. This pilot study shows first evidence that HR is related to social jetlag, and therefore warrants more studies in different shift schedules.