Influence of Rotating Shift Work and Lifestyle Factors on the Menstrual Cycle Characteristics

Abstract

ISEE-181 Objective: Shift work is a common job rotating type in high-tech industries in Taiwan. Circadian pattern may be disrupted by rotating shift work, and it may cause irregular menstruation, prolong menstruation, and other endocrine disorders in female workers. Material and Methods: We conducted this longitudinal study to investigate the menstrual cycle length (MCL) and regularity in females who were engaged in rotating shift work in a photoelectron company in 2005 in Taiwan. We selected female office workers who were not engaged in rotating shift work as comparison group. Every participant recorded details of her menstruation day, menstruation period, and ruled out pregnancy for 8 consecutive months in totally. Results: We collected 1135 cycles in study group (280 participants) and 117 cycles in comparison group (49 participants) among 329 female participants. We found mean MCL and menstrual bleeding days without difference between study group and comparison group. However, the prevalence of menstruation irregularity (150 ≤24 days or ≥35 days) was higher in study group (P = 0.04). By comparing the results between before and after engaging in rotating shift work, we found that there were increasing rates of menstruation irregularity (33.9% vs. 52.1%, P < 0.001 for McNemar test) and prolonged menstrual bleeding more than 7 days (13.4% vs. 40.0%, P < 0.001 for McNemar test). Using multivariate logistic regression analysis, it was found that prevalence of menstrual irregularity among study group was higher than among comparison group (OR = 1.71, 95% CI = 1.03–2.88). Conclusions: We found that shift work might influence MCL and menstrual bleeding days. This result will help employers and labor administration to maintain female worker's health.