Studying the menopausal transition: methodological considerations.

OBJECTIVE

To document prospectively the menopausal status of a population-based cohort of women.

METHODS

A 11-year community-based study with annual interviews of 438 Australian-born women who at baseline were aged 45-55 years, had menstruated in the previous 3 months and were not using hormone therapy or the oral contraceptive pill. Women were interviewed annually in their own homes. Each woman's menstrual history during her transition to menopause was documented prospectively using menstrual calendars.

RESULTS

After 11 years of follow-up, the retention rate was 83%. The percentages of the cohort who had experienced a natural menopause at the 3rd, 6th, 9th and 11th years of follow-up were 13%, 36%, 51% and 52%, respectively. After 11 years of follow-up, 3% of the cohort had menstruated in the previous 12 months and 18% had used hormone therapy prior to their final menstrual period.

CONCLUSION

In studying the normal transition to menopause, the baseline age of the cohort, the length of time available for follow-up, the intervention rate (hormone therapy and hysterectomy) and the number of participants all need to be considered to ensure there is sufficient power for analyses.