Abstract Body: Objective:
Night shift work disrupts normal circadian rhythms, which is hypothesized to lead to negative impacts on cardiovascular health. The underlying mechanisms remain poorly understood. We examined the associations between night shift work and cardiovascular risk factors, including blood pressure (BP), body mass index (BMI) and waist-to-hip ratio (WHR).

Materials and methods:
We used data from the Exposome Project for Health and Occupational Research study (EPHOR), which included night and day shift workers from Spain, Sweden, and Denmark. We included participants with complete data on BP, BMI, and WHR. We used linear regression for the continuous outcomes and logistic regression for the binary outcomes, adjusting for relevant confounders. We conducted sex-stratified analyses, since sex may modify the relationship between night shift work exposure and cardiometabolic outcomes.

Results:
The analytic sample comprised 805 participants, 58% of whom were night shift workers with a mean age of 42 years (SD 11). The majority were female (87%). Compared to day workers, night shift workers had a higher BMI (β coeff. 1.10, 95%CI 0.37, 1.83), a higher odds of overweight/obesity (OR 1.39, 95%CI 1.03, 1.88), and a higher odds of moderate-high risk WHR (OR 1.39, 95%CI 1.00, 1.93). Blood pressure and the odds of hypertension were also elevated among night shift workers, but 95% CIs overlapped with the null. In the sex-stratified analyses, the point estimates were elevated among women (Table 1).

Conclusion:
Compared with day workers, night shift workers showed a worse cardiometabolic profile, particularly among women, indicating that cardiometabolic problems may be compounded among female night shift workers. These findings are in line with earlier research indicating that night shift work is associated with an increased cardiometabolic risk. We plan to further explore whether shift work characteristics, for example intensity of night shifts, may influence these findings.