The association between exposure to different aspects of shift work and metabolic risk factors in health care workers, and the role of chronotype

Objective
Shift work has been linked to cardio-metabolic diseases, but insight into different shift work-related aspects and chronotype of shift workers and their relation with metabolic risk factors is limited. This study examined the association between current shift work status, frequency and duration of night shift work, chronotype, and metabolic risk factors in a population of health care workers.
Methods
Anthropometrics, questionnaires, and blood samples were collected from 503 shift working and 93 non-shift working health care workers employed in hospitals. Body mass index, waist circumference, cholesterol (total, HDL, LDL), triglycerides, and high-sensitivity C-reactive protein were measured. Associations of current shift work, frequency (non-night shift worker, 1–2, 3–4, ≥5 night shifts/month) and duration of night shift work (non-night shift workers, <10, 10–19, ≥20 years), and shift workers’ chronotype, with metabolic risk factors were studied using linear regression analysis.
Results
Compared to non-shift workers, shift workers’ total cholesterol level was 0.38 mmol/L lower (95%-CI = -0.73 –-0.04) and LDL cholesterol was 0.34 mmol/L lower (95%-CI = -0.60 –-0.08). For all other metabolic risk factors, no differences were found. The association between shift work and LDL cholesterol was especially found among shift workers working night shifts for ≥20 years (B = -0.49 (95%-CI = -0.78 –-0.19)). No differences were found for night shift frequency and chronotype.
Conclusion
In this population of health care workers employed in hospitals, no evidence for differences in metabolic risk factors was observed that could underlie a link between shift work and cardio-metabolic diseases. Further research using different aspects of shift work to study the association with metabolic risk factors is recommended.

研究目的
轮班工作已被证实与心血管代谢疾病存在关联，但目前针对轮班工作的不同维度、轮班工人的昼夜节律类型（chronotype）及其与代谢危险因素之间关联的认知仍较为有限。本研究针对医院在职医护人员群体，探讨了当前轮班工作状态、夜班工作频率与时长、轮班工人的昼夜节律类型，以及上述因素与代谢危险因素之间的关联。

研究方法
本研究共纳入503名轮班医护人员与93名非轮班医护人员，均为医院在职员工。研究收集了受试者的人体测量指标、问卷调查数据与血液样本，并检测了体质量指数、腰围、总胆固醇（total cholesterol）、高密度脂蛋白胆固醇（HDL, high-density lipoprotein cholesterol）、低密度脂蛋白胆固醇（LDL, low-density lipoprotein cholesterol）、甘油三酯以及高敏C反应蛋白（high-sensitivity C-reactive protein）水平。本研究采用线性回归分析方法，探讨了当前轮班工作状态、夜班工作频率（非夜班工人、每月1~2次夜班、3~4次夜班、≥5次夜班）、夜班工作时长（非夜班工人、<10年、10~19年、≥20年）以及轮班工人的昼夜节律类型与代谢危险因素之间的关联。

研究结果
与非轮班医护人员相比，轮班医护人员的总胆固醇水平降低0.38 mmol/L（95%置信区间：-0.73 ~ -0.04），低密度脂蛋白胆固醇水平降低0.34 mmol/L（95%置信区间：-0.60 ~ -0.08）。其余代谢危险因素未观察到显著组间差异。在夜班工作时长≥20年的轮班医护人员中，轮班工作与低密度脂蛋白胆固醇水平的关联尤为显著（回归系数B=-0.49，95%置信区间：-0.78 ~ -0.19）。未观察到夜班工作频率与昼夜节律类型对代谢危险因素的显著影响。

研究结论
在本研究纳入的医院医护人员群体中，未发现可支撑轮班工作与心血管代谢疾病之间存在关联的代谢危险因素差异证据。建议未来开展更多针对轮班工作不同维度的研究，以进一步探讨其与代谢危险因素之间的关联。