Association of Shift Work with Normal-Weight Obesity in Community-Dwelling Adults

Abstract

Background Shift work is associated with obesity and metabolic syndrome. However, this association in the normal-weight population remains unclear. This study aimed to investigate whether shift work is associated with normal-weight obesity (NWO). Methods From the nationally representative Korea National Health and Nutrition Examination Survey (KNHANES) dataset (2008 to 2011), 3,800 full-time workers aged ≥19 years with a body mass index (BMI) ≤25 kg/m2 were analysed. We defined NWO as BMI ≤25 kg/m2 and body fat percentage ≥25% in men and ≥37% in women. Working patterns were classified into “daytime,” “other than daytime,” and “shift.” Multivariable logistic regression analysis was performed to evaluate the relationship between shift work and NWO. Results Shift work was associated with higher odds of NWO than daytime work (adjusted odds ratio [aOR], 1.47; 95% confidence interval [CI], 1.04 to 2.09) and night/evening work (aOR, 1.87; 95% CI, 1.11 to 3.14) after adjustment for type of work, working hours, age, sex, BMI, 25-hydroxyvitamin D levels, homeostatic model assessment for insulin resistance, and other sociodemographic factors. In subgroup analyses, the association between shift work and NWO was more robust in those aged ≥60 years and those working ≥56 hours/week. Conclusion Shift work was associated with NWO in community-dwelling Korean adults, independent of age, sex, BMI, and other covariates.

Keywords

• shift work schedule
• obesity
• body composition
• circadian rhythm
• metabolic syndrome