Associations between shift work, sleep quality and menstrual disorders among nurses: a cross-sectional analysis study

OBJECTIVES: This study aimed to examine the associations between shift work and menstrual disorders among female nurses and to explore the potential mediating role of sleep quality in these relationships. METHODS: A cross-sectional study was conducted using data from the Nurses' Environmental & Occupational exposure and health Nexus cohort (NEON). A total of 3,544 female nurses from six hospitals in Anhui Province, China, were included. Information on shift work characteristics, sleep quality, and menstrual health was collected via structured questionnaires. Binary logistic regression was used to evaluate the associations of shift work and sleep characteristics with irregular menstrual cycles and dysmenorrhea, whereas multinomial logistic regression was applied for the three-category menstrual blood volume outcome (normal volume, hypomenorrhea, and menorrhagia). Latent class analysis (LCA) was applied to identify sleep patterns, and mediation analysis was performed to assess the indirect effect of sleep quality. RESULTS: A history of rotating shift work was associated with higher odds of irregular menstrual cycles (OR = 1.31, 95% CI: 1.03-1.65) and dysmenorrhea (OR = 1.71, 95% CI: 1.42-2.06). Notably, long-term cumulative exposure (≥ 12 years) to rotating shift work (OR = 1.61, 95% CI: 1.08-2.38) and night shifts (OR = 2.40, 95% CI: 1.22-4.71) was uniquely linked to a starkly elevated likelihood of menorrhagia. An increasing trend in the odds of dysmenorrhea was observed with higher frequency of evening or night shifts over the past year. Poor sleep quality, short sleep duration (< 6 h), prolonged sleep onset latency (> 30 min), and specific sleep patterns identified by LCA were associated with higher odds of menstrual disorders. Mediation analysis indicated that sleep quality had a significant indirect effect only on the association between shift work and irregular menstrual cycles, accounting for approximately 7.36% of the total effect. No significant mediation effect was observed for dysmenorrhea. Although indirect effects were statistically significant for hypomenorrhea and menorrhagia, the total effects were not significant, suggesting inconsistent mediation patterns. CONCLUSIONS: Shift work and poor sleep quality are associated with menstrual disorders among nurses. Mediation analysis suggests that sleep quality may represent a potential pathway underlying this association, with a statistically significant mediating effect observed in irregular menstrual cycles. These findings highlight the importance of considering both occupational scheduling and sleep health in strategies aimed at improving reproductive health in shift-working women.