LAUSR

Objective To investigate the interval from menarche to the onset of premenstrual symptoms and its relationship with menarche age. Design Cross-sectional school-based survey. Setting Urban areas of Sendai, the largest city in northeastern Japan. Participants 1422 female Japanese 10th–12th grade senior high school students participated in the survey. Main outcome measures The time of awareness of premenstrual symptoms, and the interval from menarche to the onset of premenstrual symptoms. Results 1290 students had menstruation and completed the whole survey. The median age at menarche was 12 years (IQR: 11–13 years). The prevalence of self-reported premenstrual symptoms was 49%. The median age at which students became aware of premenstrual symptoms was 15 years (IQR: 14–16 years). The median time from the onset of menarche to awareness of premenstrual symptoms was 2 years. This time was negatively correlated with menarche age (ρ=−0.47, p<0.001). A Cox proportional hazards regression analysis revealed that early menarche was significantly associated with a lower cumulative risk of developing premenstrual symptoms (OR: 0.73 (95% CI 0.58 to 0.91)). Conclusions High school students in Japan began experiencing premenstrual symptoms at around 15 years old, and within 2 years of menarche. This study suggested that social factors other than hormonal factors, such as early menarche, might be associated with the onset of premenstrual symptoms.