Objective: The ReSTAGE collaboration evaluated four menstrual markers of entry to late-stage menopausal transition. The aim of this study was to assess the additional usefulness of "persistence" in relation to a clinically accessible menstrual marker of late menopausal transition, taking age into account.
Methods: In this study, a secondary analysis of menstrual calendar data in two ReSTAGE-collaborating studies with comparatively low age at beginning of menstrual calendar observation was performed.
Results: Sixty days of amenorrhea is as useful for predicting time to the final menstrual period as the currently accepted 90-day marker for women older than 45 years. For those aged between 40 and 44 years, recurrence of the 60-day marker within the next 10 cycles is a better indicator than a single occurrence of the 60-day marker or the 90-day marker.
Conclusions: Sixty-day amenorrhea is as reliable a marker of late menopausal transition as the traditional 90-day marker for women older than 45 years. For those aged 40 to 44 years, keeping menstrual records to check for a recurrence of the 60-day marker will be useful.