Objectives: As more interest centers on the years surrounding menopause, the inconsistent use of nonspecific terminology to define these years becomes a problem. Our objective was to describe the development of specific criteria that define stages within the menopausal transition and to apply these criteria to classify midlife women into a stage of transition.
Design: A total of 184 midlife women from the Seattle Midlife Women's Health Study taking no hormones and for whom data were available about initial menstrual cycle changes were studied. Questionnaires about menstrual cycle changes and menstrual calendars were mailed yearly. Intra-individual analyses for type and chronology of menstrual cycle changes during midlife for change in flow amount or duration, cycle length change, cycle irregularity, or skipped periods were conducted.
Results: Changes in flow or cycle length most frequently preceded irregularity without skipped periods, which preceded skipped periods. Initial changes began in the early 30s and most frequently between ages 40 and 44. Only 14% had irregularity as the initial change. Three stages of the menopausal transition were identified: early (flow and/or cycle length changes), middle (irregularity without skipping), and late (skipped periods). Age did not differentiate the three stages.
Conclusions: These findings provide evidence for a progression of menstrual cycle events through the menopausal transition, which form the basis for three stages of the transition: early, middle, and late transition. Studies about the entire transition need to include women younger than 45. Both menstrual calendars and questionnaire data are needed to identify these three stages, and precise definitions of irregularity and skipped period are necessary.