Effect of circadian rhythm type on serum lipid levels in shift workers: A 5-year cohort study

ABSTRACTWe investigated how differences in circadian rhythm type affect the health of workers engaged in shift work. Employees, who were newly hired in a steel company between 2007 and 2011, received the Morningness–Eveningness Questionnaire (MEQ) survey. The target participants were 153 male shift workers who were not being treated with any antihyperlipidemic drugs and underwent periodic physical examinations including blood tests at least twice. According to the score of the MEQ at the time of joining the company, we classified the subjects into five types. Longitudinal changes in serum lipid level were estimated among the circadian rhythm types adjusted for age, BMI, and other covariates using a linear mixed model. The regression coefficient of total cholesterol level in the “definitely and moderately morning” group was −17.83 (95% confidence interval (CI): −33.42 to −2.23), and in the “intermediate ‘group’ was −16.84 [95% CI: −30.40 to −3.28], compared to the moderate evening type.” The total choleste...