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Objective: To determine whether secondary amenorrhea during teenage years influences bone mineral density (BMD) in female athletes in their 20s. Design: Original research. Setting: Japan Institute of Sports Sciences. Participants: Two hundred ten elite female athletes older than 20 years were included in the study. Main Outcome Measures: Information on the participants' past (ie, during their teenage years) and current menstrual cycle, training time, history of stress fractures, and blood tests for hormones received was obtained. Bone mineral density of the lumbar spine was evaluated by dual-energy x-ray absorptiometry; low BMD was defined as a Z-score ≤-1. We investigated the correlation factors for low BMD in athletes in their 20s by univariable and multivariable logistic regression analysis. Results: A total of 39 (18.6%) female athletes had low BMD. Secondary amenorrhea in their teens [odds ratio (OR), 7.11, 95% confidence interval (CI), 2.38-21.24; P < 0.001] and present body mass index (BMI) (OR, 0.56, 95% CI, 0.42-0.73; P < 0.001) were independent correlation factors for low BMD in the multivariable logistic regression analysis. The average Z-score for those with secondary amenorrhea in their teens and 20s, secondary amenorrhea in their 20s only, and regular menstruation was -1.56 ± 1.00, -0.45 ± 1.21, and 0.82 ± 1.11 g/cm2, respectively. Conclusions: Secondary amenorrhea for at least 1 year during teenage years in female athletes and BMI at present was strongly associated with low BMD in their 20s. [ABSTRACT FROM AUTHOR]

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., (© 2020 The Authors. Journal of Occupational Health published by John Wiley & Sons Australia, Ltd on behalf of The Japan Society for Occupational Health.)