Association of prolonged occupational co-exposures to electromagnetic fields, noise, and rotating shift work with thyroid hormone levels.

The purpose of this study was to determine the association of prolonged occupational co-exposure to extremely low-frequency electromagnetic fields (ELF-EMFs), noise, and rotating shift work with the levels of thyroid hormones (triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH). From 2016 to 2017, we enrolled all male workers without a history of thyroid disorders and followed them until 2020. To measure ELF-EMFs and noise exposures, we calculated the 8-hour equivalent sound pressure levels (Leq) and the 8-hour average of ELF-EMFs, respectively. Shift work schedules involved 8-hr fixed day and 8-hr clockwise 3-rotating night schedules. The participant's thyroid hormone levels were obtained from blood test results in their medical records. The percentage change in the levels of T3, T4, and TSH was estimated by using different mixed-effects linear regression models. The TSH levels were significantly elevated per a 10-dB increment of noise. The levels of T4 hormone were significantly changed per a unit increase in the levels of ELF-EMFs. Compared to the fixed-day workers, we observed workers exposed to shift work had a significantly lower T4 level. For T4 and TSH hormones, we found significant interactions among noise, ELF-EMFs, and shift work variables. In summary, this study warranted that prolonged exposure to ELF-EMFs, noise, and rotating shift work might be associated with thyroid dysfunction.

The effects of rotating and extended night shift work on the prevalence of metabolic syndrome and its components.

BACKGROUND: Some studies indicated night shift work can be associated with the higher risk of metabolic syndrome (MetS). However, the effect of both rotating and extended night shift work (12-hr rotating night) on MetS has not well-known. We aimed to examine and clarify the association among petrochemical workers. METHODS: We recruited 1575 eligible workers in this study. According to shift work schedules the participants were divided into following groups: 12-hr fixed day and 12-hr rotating night. Biochemical data, including fasting blood sugar and lipid panel (TC, TG, LDL, and HDL) were determined by blood tests. Demographic data was obtained by interview at the time of blood pressure and anthropometric indices measurements. The National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) was applied to identify subjects with MetS. The Logistic regression models were used to predict risk of MetS and its components between study groups. RESULTS: The prevalence of MetS was showed 18.4% (290/1575). We found a significant difference between study groups in the prevalence of MetS (p < 0.05). The odds ratios (ORs) and 95% confidence intervals (CIs) in the 12-hr rotating night group in comparison to the 12-hr fixed day shift group according to unadjusted and full adjusted logistic regression models were estimated 1.26 (0.96, 1.65) and 1.34 (1.01, 1.76), respectively. Among MetS components, we observed the significant higher risk in TG and HDL (P < 0.05). CONCLUSION: This study suggests 12-hr rotating night shift as the high-risk group for MetS. More studies needed to confirm our findings.