title: [Changes of semen parameters in Chinese fertile men in the past 25 years].
abstract: OBJECTIVE
  To analyze the changes of seminal parameters in Chinese fertile men during the past 25 years.
  
  
  METHODS
  We collected semen samples from 5,834 fertile men in 14 different provinces (including Beijing) between 1980 and 2005 and retrospectively studied their seminal parameters, abstinence durations and total testis volumes by meta-analysis.
  
  
  RESULTS
  Compared with the first 15 years, a significant decrease was observed in both sperm density and total number of sperm per ejaculate in the semen samples collected between 1996-2000 (P < 0.0001 and P < 0.05), but not obvious in those between 1996-2000 and after 2005 (P > 0.05). As for sperm motility, no time-related changes were noted (P > 0.05) except a reduction with the increase of age.
  
  
  CONCLUSIONS
  There was a decline in sperm density and total number of sperm per ejaculate in Chinese fertile men over the past 25 years, although not significant in the latter 10 years since 1996, but with no time-related changes in sperm motility.
authors.affiliation: Research Institute of Science and Technology, National Population and Family Planning Commission of China WHO Collaborating Center for Research in Human Reproduction, Beijing 100081, China. lxwbj@yahoo.com.cn
authors.forename: Xiao-Wei
authors.initials: XW
authors.lastname: Liang
authors.forename: Wen-Hong
authors.initials: WH
authors.lastname: Lu
authors.forename: Zhen-Wen
authors.initials: ZW
authors.lastname: Chen
authors.forename: Xing-Hai
authors.initials: XH
authors.lastname: Wang
authors.forename: Heng
authors.initials: H
authors.lastname: Zhao
authors.forename: Gui-Yuan
authors.initials: GY
authors.lastname: Zhang
authors.forename: Yi-Qun
authors.initials: YQ
authors.lastname: Gu
mesh_terms: D000328:Adult; D002681:China; D005298:Fertility; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D012661:Semen; D013076:Sperm Count / Q000706:statistics & numerical data*; D013081:Sperm Motility