Abstract Objectives In Japan, the prevalence of irregular menstrual cycles and its association with the frequency of night shifts have scarcely assessed. The present study aimed to evaluate the relationship between irregular menstrual cycles and the frequency of night shifts in Japanese female nurses. Methods We conducted a cross‐sectional web‐based self‐administered questionnaire survey in 2019. An irregular menstrual cycle was defined as a cycle length of ≤21 days or ≥39 days at least a few times over the past year or amenorrhea for at least 3 months. We used Poison regression analysis with a robust error variance to calculate the prevalence ratios adjusted for age, body mass index, hospital size, and the department in which they worked. Results A total of 1249 women were included, and 679 (54.4%) and 195 (15.6%) of them worked under two and three rotating shifts. The prevalence of irregular menstrual cycles was 24.8%, 37.4%, and 35.9% in the no night, two rotating, and three rotating shifts groups, respectively. While the frequency of night shifts had a dose‐responsive relationship with irregular menstrual cycles in the two rotating shifts group, it was not observed in the three rotating shifts group. However, the risk of work getting affected by dysmenorrhea or premenstrual symptoms increased in the three rotating shifts group. Conclusions Over 30% of Japanese female nurses working under night shifts had irregular menstrual cycles. The high frequency of night shifts increased the risk of irregular menstrual cycles and secondary amenorrhea in the two rotating shifts group.

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两班或三班轮班制的日本护士夜班频率和月经周期特征

摘要 目的在日本，几乎没有评估月经周期不规则的流行及其与夜班频率的关系。本研究旨在评估日本女护士不规律的月经周期与夜班频率之间的关系。方法 我们在 2019 年进行了一项基于网络的横断面自填问卷调查。不规则月经周期定义为过去一年至少几次周期长度≤21 天或≥39 天或至少闭经3个月。我们使用具有稳健误差方差的 Poison 回归分析来计算根据年龄、体重指数、医院规模和他们工作的部门调整的患病率。结果共纳入1249名女性，其中679名（54.4%）和195名（15. 6%) 他们在两班和三班轮班下工作。无夜班、两班轮班组和三班班组的月经周期不规律发生率分别为24.8%、37.4%和35.9%。虽然在两班轮班组中夜班频率与不规则月经周期具有剂量反应关系，但在三班班组中未观察到。然而，在三班轮班组中，工作受到痛经或经前症状影响的风险增加。结论 30%以上的日本夜班女护士月经周期不规律。高频率的夜班增加了两班轮班组出现月经周期不规则和继发性闭经的风险。无夜班、两班轮班组和三班轮班组分别为 35.9%。虽然在两班轮班组中夜班频率与不规则月经周期具有剂量反应关系，但在三班班组中未观察到。然而，在三班轮班组中，工作受到痛经或经前症状影响的风险增加。结论 30%以上的日本夜班女护士月经周期不规律。高频率的夜班增加了两班轮班组出现月经周期不规则和继发性闭经的风险。无夜班、两班轮班组和三班轮班组分别为 35.9%。虽然在两班轮班组中夜班频率与不规则月经周期具有剂量反应关系，但在三班班组中未观察到。然而，在三班轮班组中，工作受到痛经或经前症状影响的风险增加。结论 30%以上的日本夜班女护士月经周期不规律。高频率的夜班增加了两个轮班组的月经周期不规则和继发性闭经的风险。虽然在两班轮班组中夜班频率与不规则月经周期具有剂量反应关系，但在三班班组中未观察到。然而，在三班轮班组中，工作受到痛经或经前症状影响的风险增加。结论 30%以上的日本夜班女护士月经周期不规律。高频率的夜班增加了两班轮班组出现月经周期不规则和继发性闭经的风险。虽然在两班轮班组中夜班频率与不规则月经周期具有剂量反应关系，但在三班班组中未观察到。然而，在三班轮班组中，工作受到痛经或经前症状影响的风险增加。结论 30%以上的日本夜班女护士月经周期不规律。高频率的夜班增加了两班轮班组出现月经周期不规则和继发性闭经的风险。结论 30%以上的日本夜班女护士月经周期不规律。高频率的夜班增加了两班轮班组出现月经周期不规则和继发性闭经的风险。结论 30%以上的日本夜班女护士月经周期不规律。高频率的夜班增加了两班轮班组出现月经周期不规则和继发性闭经的风险。