The relationship between shift work and metabolic syndrome: a prospective cohort study

Background: Metabolic syndromes have been identified as a major risk factor for people with cardiovascular disease. Metabolic syndromes are defined as a range of conditions including waist-fat, abdominal obesity, high blood pressure, diabetes, high triglycerides, and HDL. Considering the importance of controlling metabolic syndrome, the research study subject with the mentioned aim is so important in the world and Iran. One of the affecting factors that have reported contradictory results in the previous study are shift work. Therefore, this prospective cohort study was conducted to investigate the relationship between metabolic shift syndromes on labor men. Methods: This five-year prospective cohort study has been conducted in randomly selected workers (using random cluster sampling) who work in Esfahan’s Mobarakeh Steel Company (the largest steel company in Iran country that located in Mobarkeh city in Isfahan province, Iran) from April 2011 March 2015. In this study shiftwork and metabolic syndromes considered as an independent and dependent variable respectively. In addition, age, education and work experience considered as a controlling variable. In this study, routinely rotating (ROR) and weekly rotating (WRO) shifts were scheduled with a clockwise rotation plan (two mornings, two evenings, two night and two days off for ROR and three morning shifts, three evening shifts, and one day off every two weeks, Fridays always off for WRO shifts). The morning, evening, and night shifts began at 7 AM, 3 PM, and 11 PM, respectively. Day workers (DW) worked from 7 AM to 3 PM on weekdays and had Thursdays and Fridays off. Results: The study sample included 1321 male workers (mean age=43). Among these subjects, 528 (40%), 155 (12%) and 638 (48%) were day workers, WRO shift workers, and ROR. The 5-year odds ratio (OR) of metabolic syndrome in the ROR shift worker compared to the DW was OR=1.93, P-value=0.044 and for a WRO shift with OR=1.26, P=0.64. Conclusion: Considering the result of this study increased risk of metabolic syndrome in ROR shift worker rather than DW has been approved but such increase in WRO shift rather day worker had not to be approved.