Explain "Menarche" and "Menopause" with the help of a diagram.
Answers
Answer:
Background
Studies conducted in Western countries suggest that early age at menarche and early age at menopause are both associated with increased total mortality, but limited data are available for Asian populations. We examined associations of age at menarche and natural menopause and duration of the reproductive span with mortality in a population-based cohort study of Chinese women.
Methods
We evaluated the effects of age at menarche, age at natural menopause, and number of reproductive years on total and cause-specific mortality among 31,955 naturally menopausal Chinese women who participated in the Shanghai Women's Health Study, a population-based, prospective cohort study.
Results
A total of 3,158 deaths occurred during a median follow-up of 11.2 years. Results from Cox proportional hazards models showed that younger age at menopause (<46.64 years) was associated with higher risk of total mortality (Ptrend = 0.02). Younger age at menarche (<14 years) was associated with higher risk of mortality from stroke (Ptrend = 0.03) and diabetes (Ptrend = 0.02) but lower risk of mortality from respiratory system cancer (Ptrend = 0.01). Women with a shorter reproductive span had lower risk of mortality from gynecological cancers (Ptrend = 0.03).
Conclusions
Our study found that menstrual characteristics are important predictors of mortality, suggesting an important role of sex hormones in biological aging.
Citation: Wu X, Cai H, Kallianpur A, Gao Y-T, Yang G, Chow W-H, et al. (2014) Age at Menarche and Natural Menopause and Number of Reproductive Years in Association with Mortality: Results from a Median Follow-Up of 11.2 Years among 31,955 Naturally Menopausal Chinese Women. PLoS ONE 9(8): e103673. doi:10.1371/journal.pone.0103673
Editor: Olga Y. Gorlova, Geisel School of Medicine at Dartmouth College, United States of America
Received: January 24, 2014; Accepted: July 1, 2014; Published: August 4, 2014
Copyright: © 2014 Wu et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work was supported by a grant from the United States National Cancer Institute at the US National Institutes of Health [grant number R37 CA070867, PI: W. Zheng]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Answer:
Menarche (/mɪˈnɑːrkiː/ mi-NAR-kee; Greek: μήν mēn "month" + ἀρχή arkhē "beginning") is the first menstrual cycle, or first menstrual bleeding, in female humans. From both social and medical perspectives, it is often considered the central event of female puberty, as it signals the possibility of fertility.
Girls experience menarche at different ages. The timing of menarche is influenced by female biology, as well as genetic and environmental factors, especially nutritional factors. The mean age of menarche has declined over the last century, but the magnitude of the decline and the factors responsible remain subjects of contention. The worldwide average age of menarche is very difficult to estimate accurately, and it varies significantly by geographical region, race, ethnicity and other characteristics. Various estimates have placed it at 13.[1] There is a later age of onset in Asian populations compared to the West.[2] The average age of menarche is about 12.5 years in the United States,[3] 12.7 in Canada,[4] and 12.9 in the UK.[5] A study of girls in Istanbul, Turkey, found the median age at menarche to be 12.7 years.[6]