title: Canadian semen quality: an analysis of sperm density among eleven academic fertility centers.
abstract: OBJECTIVE
  To determine whether sperm quality has declined among Canadian men during the past 13 years and whether there are regional differences in sperm quality.
  
  
  METHODS
  Retrospective temporal series of cross-sectional studies.
  
  
  METHODS
  University fertility centers across Canada.
  
  
  METHODS
  Men being investigated as part of the normal infertility work-up.
  
  
  METHODS
  Sperm concentrations among all the samples were compared on an annual basis to assess any changes over 13 years from 1984 through 1996.
  
  
  RESULTS
  There were regional differences and trends in both up and down directions. Linear regression analysis of the means of each center for each year showed no significant trend. However, when all the samples were analyzed by regression analysis there was a significant downward trend.
  
  
  CONCLUSIONS
  Linear regression analysis showed a significant downward trend in sperm concentration among 48,968 samples from Canadian men obtained from 1984 through 1996. A significant difference was seen in the mean concentrations between centers, ranging from 48.6 to 104.5 X 10(6)/mL. Secular trends in sperm density are dependent on the statistical method used for analysis.
authors.affiliation: Department of Obstetrics and Gynecology, McMaster University, Health Sciences Centre, Hamilton, Ontario, Canada. younglai@fhs.csu.mcmaster.ca
authors.forename: E V
authors.initials: EV
authors.lastname: Younglai
authors.forename: J A
authors.initials: JA
authors.lastname: Collins
authors.forename: W G
authors.initials: WG
authors.lastname: Foster
mesh_terms: D002170:Canada / Q000453:epidemiology; D006801:Humans; D007248:Infertility, Male / Q000453:epidemiology / Q000503:physiopathology*; D008297:Male; D012044:Regression Analysis; D012661:Semen / Q000502:physiology*; D013076:Sperm Count