Effects of shift work on abdominal obesity among 20–39-year-old female nurses: a 5-year retrospective longitudinal study

BACKGROUND This study aimed to investigate the effects of shift work on abdominal obesity among young and middle-aged female nurses during a 5-year retrospective study. METHODS This retrospective study included female nurses (20-39 years old) who worked at a university hospital in Korea and had available health screening results from 2010-2015. Among 2,611 employees, 934 healthy 20-39-year-old female nurses were identified, and data regarding their demographic information (age and date of employment), waist circumferences (WC), and lifestyle factors (alcohol and exercise) were obtained. Abdominal obesity was defined as a WC of ≥80 cm, based on the World Health Organization's Asia-West Pacific standard in 2000. The mean WC change from baseline was analyzed using the paired t test, and the association between shift work and abdominal obesity was analyzed using the generalized estimating equation. RESULTS Compared to all day workers (both age groups), the 20-29-year-old nurses did not exhibit significant changes in WC at each follow-up. However, among the 30-39-year-old nurses, shift workers exhibited a significant change in WC (vs. baseline) during years 4 and 5, compared to day workers. After adjusting for effective confounders and stratifying the participants according to age, the 20-29-year-old nurses exhibited an odds ratio of 3.21 (95 % confidence interval: 1.29-7.98) for shift work-associated obesity, although the odds ratio for the 30-39-year-old nurses was not statistically significant. CONCLUSION In the study population, shift work was associated with a significant change in mean WC among 30-39-year-old nurses, and the shift work-associated risk of abdominal obesity was significant among 20-29-year-old nurses. These results indicate that shift work may influence abdominal obesity differently in 20-29-year-old and 30-39-year-old female nurses.