title: Semen quality of 324 fertile Japanese men.
abstract: BACKGROUND
  A number of studies have indicated regional differences in semen quality. To examine the current status in Japan, we undertook a cross-sectional study on the semen quality of fertile Japanese men for comparison with recent European results.
  
  
  METHODS
  Semen parameters of 324 fertile men from the Kawasaki/Yokohama area were investigated. The semen parameters were compared with those published for fertile men from four European cities, Copenhagen, Paris, Edinburgh and Turku.
  
  
  RESULTS
  When adjusting for confounders such as ejaculation abstinence period and age, the lowest sperm concentrations were detected in men from Kawasaki/Yokohama followed by men from Copenhagen, Paris, Edinburgh and Turku, but only the differences between men from Kawasaki/Yokohama and men from Edinburgh and Turku were significant (P=0.0008 and P<0.0001, respectively). Total sperm count, percentage of motile sperm and percentage of normal sperm observed in Kawasaki/Yokohama were significantly lower than those from all European centres except for motile sperm in men from Paris.
  
  
  CONCLUSIONS
  Japanese fertile men had a semen quality at the level of Danish men, who have been reported to have the lowest among investigated men in Europe. The low level of semen quality of the fertile Japanese men may be due to lifestyle or other environmental factors; however, ethnic differences caused by different genetic variation or combinations cannot be ruled out by this study.
authors.affiliation: Department of Urology, St Marianna University School of Medicine, 216-8511 Kawasaki, Japan. t4iwa@marianna-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Iwamoto
authors.forename: S
authors.initials: S
authors.lastname: Nozawa
authors.forename: M
authors.initials: M
authors.lastname: Yoshiike
authors.forename: T
authors.initials: T
authors.lastname: Hoshino
authors.forename: K
authors.initials: K
authors.lastname: Baba
authors.forename: T
authors.initials: T
authors.lastname: Matsushita
authors.forename: S N
authors.initials: SN
authors.lastname: Tanaka
authors.forename: M
authors.initials: M
authors.lastname: Naka
authors.forename: N E
authors.initials: NE
authors.lastname: Skakkebaek
authors.forename: N
authors.initials: N
authors.lastname: Jørgensen
mesh_terms: D004542:Ejaculation; D005060:Europe; D005260:Female; D005298:Fertility / Q000502:physiology*; D006801:Humans; D007564:Japan; D008297:Male; D010298:Parity; D010808:Physical Examination; D011247:Pregnancy; D015203:Reproducibility of Results; D012661:Semen / Q000502:physiology*; D012725:Sexual Behavior; D013076:Sperm Count; D011795:Surveys and Questionnaires