An event history analysis of age at last menstrual period: correlates of natural and surgical menopause among midlife Wisconsin women

Population aging coupled with heightened consumerism among those using the health care system have increased public and research interest in menopause. Despite these trends, we know little about the process of menstrual cessation. This paper reviews previous claims regarding secular trends in menopausal age by considering how menstrual cessations differ by type: (1) that due to surgical intervention such as hysterectomy, and (2) that due to "natural" (non-surgical) menopause. Analyses of menopause that exclude hysterectomized women are flawed, because such women constitute a high proportion of American women at midlife. Competing risk survival analysis techniques are applied to model the shape of the underlying hazards for reproductive organ surgery versus "natural" menopause among 3506 midlife women from the Wisconsin Longitudinal Study. Weibull models are used to evaluate effects of a variety of possible correlates (including education, mental ability, occupation, family background, fertility experience, smoking behavior and hormone therapy). While socioeconomic parameters do contribute to observed differences in age at menstrual cessation, these factors operate through more proximate health-related behaviors (such as smoking in the case of natural menopause and fertility for surgical menopause).