title: Trends of age at menarche and association with body mass index in Chinese school-aged girls, 1985-2010.
abstract: OBJECTIVE
  To estimate the shifts in age at menarche from 1985 to 2010, compare the differences of average age at menarche between urban and rural groups, and determine the association of menarche with body mass index (BMI).
  
  
  METHODS
  The data were obtained from 4 cross-sectional Chinese National Surveys on Students' Constitution and Health (1985, 1995, 2005, and 2010). In this representative sample of Chinese school-aged girls, the average age at menarche was determined using probit analysis and compared between urban and rural areas. Logistic regression was used to assess the association of BMI with the likelihood of having reached menarche.
  
  
  RESULTS
  The age at menarche in Chinese girls dropped from 13.41 years to 12.47 years from 1985 to 2010. There was a significant difference in age at menarche between urban and rural girls over time, with urban girls having their menarche earlier than rural girls. Logistic regression showed that a higher BMI was strongly associated with an increased likelihood of having reached menarche, even after controlling for age, urban or rural residence, province, social economic status, and school.
  
  
  CONCLUSIONS
  The analysis suggests a drop of about 4.5 months per decade in the average age at menarche over the past 25 years, and a significant inverse association between BMI and having reached menarche. Considering that both early menarche and higher BMI are significant risk factors for chronic diseases, and may act together in later years to the detriment of a woman's health, greater attention should be paid to the health of girls with earlier menarche and higher BMI.
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, China; Division of Social Medicine and Global Health, Department of Clinical Sciences, Lund University, Malmö, Sweden.
authors.forename: Yi
authors.initials: Y
authors.lastname: Song
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Ma
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, China. Electronic address: whjun1@bjmu.edu.cn.
authors.forename: Hai-Jun
authors.initials: HJ
authors.lastname: Wang
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, China; Centre for Chronic Disease, School of Medicine, University of Queensland, Royal Brisbane and Women's Hospital, Herston, Australia.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, China.
authors.forename: Peijin
authors.initials: P
authors.lastname: Hu
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Division of Social Medicine and Global Health, Department of Clinical Sciences, Lund University, Malmö, Sweden.
authors.forename: Anette
authors.initials: A
authors.lastname: Agardh
mesh_terms: D000293:Adolescent; D044466:Asian People; D015992:Body Mass Index; D002648:Child; D002681:China; D005260:Female; D006801:Humans; D016015:Logistic Models; D008572:Menarche / Q000502:physiology*; D012016:Reference Values; D012923:Social Class