P-726 Age of natural menopause and its associated factors among ethnic Han and Tibetan Chinese women: findings from a China Multi-Ethnic Cohort (CMEC) study

Abstract Study question Is there a disparity in the age of natural menopause (ANM) between ethnic Han and Tibetan Chinese women? Summary answer The present study has discovered a significant difference in the ANM between ethnic Han and Tibetan Chinese women. What is known already The ANM indicates the termination of ovarian function and the reproductive lifespan of the ovary. Factors influencing ANM include genetic, ovarian diseases or surgery, environment, and unhealthy lifestyles. Some studies reported that ANM was different among different ethnics, such as lower in African, Latin American, Asian, whereas higher in Europe, Australia and America. Ethnic Tibetan Chinese mainly resides in an environment with high altitude, low oxygen level, and intense ultraviolet radiation. They also have unique dietary and lifestyle habits, which might result in different ANM compared to ethnic Han Chinese. However, there are few studies on ANM between the two. Study design, size, duration We performed a cross-section study involving 11174 ethnic Han and 1049 ethnic Tibetan Chinese postmenopausal women from Chengdu city and Aba Prefecture in Sichuan province. The participants were recruited by the China Multi-Ethnic Cohort (CMEC) study from May 2018 to September 2019. Participants/materials, setting, methods Information of the postmenopausal women was derived from CMEC baseline questionnaire. Ethnicity was used as the primary exposure variable. Regression models incorporating linear, quadratic and quadratic with interaction terms on age were used to assess the association of ANM with the ethnicity. Main results and the role of chance The mean ANM of ethnic Han Chinese women was later than that of ethnic Tibetan Chinese women (48.50 ± 4.20 years vs. 47.80 ± 4.92 years, P < 0.05). Multivariate linear regression analysis showed a significant disparity in the ANM between the two groups, and sexual life, higher education, no smoking, never experienced severe food shortage, later age of menarche and more times of pregnancy were associated with later ANM (P < 0.05). Furthermore, the quadratic and interaction models demonstrated a significant non-linear association between the ANM and the age at the time of survey. In both groups, the ANM showed a trend of first rising and then declining with the increase of the age at the time of survey Notably, among women younger than 68, the ANM of ethnic Han Chinese was significantly later than that of ethnic Tibetan Chinese. Limitations, reasons for caution The information regarding menopausal women, including ANM and potential influencing factors were obtained from self-reports. Additionally, the duration of exposure to these potential influencing factors remained uncertain. Wider implications of the findings This is the first study with a large sample size comparing ANM between ethnic Han and Tibetan Chinese women. Notably, the age at the time of survey and ethnicity have independently contributed to variation in ANM, and significant interaction effects on ANM are found between age of survey and ethnicity. Trial registration number not applicable