Night-shift work and its association with metabolic syndrome

This study explores the correlation between metabolic syndrome and night-shift work in Taiwan by analyzing employees' annual health check data (March 2019). More than 9000 records were enrolled. Through the analysis of the annual health check data of a semiconductor factory's day-shift and night-shift workers' metabolic syndrome indicators, the relationship between night-shift work and metabolic syndrome was identified. According to the definition of long-term night work labor by the Ministry of Labor of Taiwan, this study divides all employees of the factory into long-term night work and non-long-term night work employees. Abnormal waist circumference (WC) was defined as WC ≥ 90 cm in males and WC ≥ 80 cm in females. Abnormal blood pressure was defined as systolic blood pressure ≥ 130 mm Hg, diastolic blood pressure ≥ 85 mm Hg, or taking medication for hypertension. Abnormal fasting blood sugar was defined as ≥100 mg/dL or taking medication for diabetes. Elevated triglyceride (TG) was defined as TG ≥ 150 mg/dL or taking TG-lowering medication. Abnormal high-density lipoprotein (HDL) was defined as HDL < 40 mg/dL in males and HDL < 50 mg/dL in females. A total of 9322 workers from the factory were recruited: 4039 workers were night-shift employees, and 5283 workers were non-night-shift employees. Night work status increased the risk of poor blood pressure (systolic pressure + 3.1%, diastolic pressure + 1.7%) and elevated TG (+5.7%). Night-shift workers had a higher body mass index and abdominal circumference than day-shift workers. Night-shift workers had a 3.6% higher risk of obesity/overweight. Logistic regression analysis demonstrated that, after adjusting for age, sex, and body mass index, night-shift work was significantly associated with a higher risk of metabolic syndrome (odds ratio = 1.17, 95% confidence interval 1.02-1.35). This study supports the hypothesis that circadian rhythm disruption plays a role in the development of metabolic syndrome. It is recommended that business units implement targeted health promotion strategies, including regular health screening, nutrition guidance, onsite exercise support, and psychosocial well-being programs. Future research should include longitudinal designs and sleep quality assessments to clarify causality.