title: Age at spermarche: 15-year trend and its association with body mass index in Chinese school-aged boys.
abstract: Little is known about the secular trends in age at spermarche among boys, and the association between body mass index (BMI) and male puberty is controversial.
  
  
  
  This study aimed to estimate the trend in age at spermarche in China and explore the association of spermarche with BMI.
  
  
  
  We used four cross-sectional Chinese National Surveys on Students' Constitution and Health (CNSSCH; 1995, 2000, 2005 and 2010). Median age at spermarche was determined using probit analysis. Logistic regression was used to assess the association of spermarche with BMI.
  
  
  
  Age at spermarche among Chinese boys dropped from 14.57 to 14.03 years from 1995 to 2010 with a decrease of 4.3 months per decade. Boys with BMI-for-age z-score lower than -2 had the latest age at spermarche. A higher BMI or BMI-for-age z-score was associated with an increased likelihood of having reached spermarche, and this association was consistently observed at all survey points.
  
  
  
  This study provides important evidence of a secular trend of earlier age at spermarche over the past 15 years in China, and this decrease was accompanied by a simultaneous increase in BMI. Strategies and interventions focusing on thinness may promote both their nutritional status and puberty development among Chinese boys.
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, China.|Social Medicine and Global Health, Department of Clinical Sciences, Lund University, Malmö, Sweden.
authors.forename: Y
authors.initials: Y
authors.lastname: Song
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, China. majunt@bjmu.edu.cn.
authors.forename: J
authors.initials: J
authors.lastname: Ma
authors.affiliation: Institute of Child and Adolescent Health, School of Public Health, Peking University, Beijing, China. whjun1@bjmu.edu.cn.
authors.forename: H-J
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, Health Sciences Building, Royal Brisbane and Women's Hospital, Herston, Australia.
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Physical Education, Hong Kong Baptist University, Hong Kong, China.
authors.forename: P W C
authors.initials: PW
authors.lastname: Lau
authors.affiliation: Social Medicine and Global Health, Department of Clinical Sciences, Lund University, Malmö, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Agardh
mesh_terms: D000293:Adolescent; D044466:Asian People; D015992:Body Mass Index; D002648:Child; D002681:China; D003430:Cross-Sectional Studies; D006801:Humans; D016015:Logistic Models; D008297:Male; D009752:Nutritional Status; D011627:Puberty / Q000208:ethnology* / Q000502:physiology; D012741:Sexual Maturation; D013851:Thinness / Q000208:ethnology* / Q000503:physiopathology
keywords: body mass index; puberty; spermarche