Is menopause still evolving? Evidence from a longitudinal study of multiethnic populations and its relevance to women's health.

BACKGROUND: To reflect on the impact of changing patterns of delayed marriage and reproduction and to seek evidence as to whether menopause is still evolving, characteristics of the menopause transition were investigated within and between ethnic populations in this study. METHODS: A cross-sectional analysis was conducted using data on 747 middle-aged women obtained from the Study of Women's Health Across the Nation (SWAN) from 1996 to 2008. The ethnic groups included: Afro-American, Chinese, Japanese, Caucasian, and Hispanic. Perimenopause age and duration, menopause age, and hormonal indicators of menopause were examined across five ethnicities. RESULTS: We found a similar window of menopause age within populations, but no significant difference in perimenopause and menopause age between populations. The rate of increase of follicle-stimulating hormone and testosterone differed significantly in Hispanics and African-Americans during the menopause transition period. CONCLUSIONS: The broad window of variation in age at menopause within the population and the absence of significant differences between populations, in combination with population variation in menopause symptoms, suggest that menopause is a relatively recently evolved and still evolving trait. Under the mate choice theory of menopause, menopause is the result of the accumulation of infertility mutations in older women due to men's preference for younger mates. We propose a shifting mate choice-shifting menopause model which posits that, as the age of mate choice/marriage shifts to older ages, so will the age at menopause, and that menopause is a transient phase of female fertility; it can de-evolve, be delayed, if not disappear completely. Integrated longitudinal menopausal studies linked with genomics and hormonal studies on diverse ethnic populations can provide valuable information bearing on women's health and personalized medicine.