title: Semen quality of 1559 young men from four cities in Japan: a cross-sectional population-based study.
abstract: OBJECTIVE
  To provide information of semen quality among normal young Japanese men and indicate the frequency of reduced semen quality.
  
  
  METHODS
  Cross-sectional, coordinated studies of Japanese young men included from university areas. The men had to be 18-24 years, and both the man and his mother had to be born in Japan. Background information was obtained from questionnaires. Standardised and quality-controlled semen analyses were performed, reproductive hormones analysed centrally and results adjusted for confounding factors.
  
  
  METHODS
  Four study centres in Japan (Kawasaki, Osaka, Kanazawa and Nagasaki).
  
  
  METHODS
  1559 men, median age 21.1 years, included during 1999-2003.
  
  
  METHODS
  Semen volume, sperm concentration, total sperm count, sperm motility, sperm morphology and reproductive hormone levels.
  
  
  RESULTS
  Median sperm concentration was 59 (95% CI 52 to 68) million/ml, and 9% and 31.9% had less than 15 and 40 million/ml, respectively. Median percentage of morphologically normal spermatozoa was 9.6 (8.8 to 10.3)%. Small, but statistically significant, differences were detected for both semen and reproductive hormone variables between men from the four cities. Overall, the semen values were lower than those of a reference population of 792 fertile Japanese men.
  
  
  CONCLUSIONS
  Assuming that the investigated men were representative for young Japanese men, a significant proportion of the population had suboptimal semen quality with reduced fertility potential, and as a group they had lower semen quality than fertile men. However, the definitive role-if any-of low semen quality for subfertility and low fertility rates remain to be investigated.
authors: Division of Male Infertility, Centre for Infertility and IVF, International University of Health and WelfareHospital, Nasushiobara, Japan.
authors: Teruaki
authors: T
authors: Iwamoto
authors: Shiari
authors: S
authors: Nozawa
authors: Makiko Naka
authors: MN
authors: Mieno
authors: Katsunori
authors: K
authors: Yamakawa
authors: Katsuyuki
authors: K
authors: Baba
authors: Miki
authors: M
authors: Yoshiike
authors: Mikio
authors: M
authors: Namiki
authors: Eitetsu
authors: E
authors: Koh
authors: Jiro
authors: J
authors: Kanaya
authors: Akihiko
authors: A
authors: Okuyama
authors: Kiyomi
authors: K
authors: Matsumiya
authors: Akira
authors: A
authors: Tsujimura
authors: Hiroshi
authors: H
authors: Kanetake
authors: Jiro
authors: J
authors: Eguchi
authors: Niels E
authors: NE
authors: Skakkebaek
authors: Matti
authors: M
authors: Vierula
authors: Jorma
authors: J
authors: Toppari
authors: Niels
authors: N
authors: Jørgensen
references: Hum Reprod. 2001 May;16(5):1012-9
references: 11331653
references: Int J Androl. 2008 Sep;31(5):499-507
references: 17651398
references: Int J Cancer. 1994 Oct 1;59(1):33-8
references: 7927900
references: Hum Reprod. 2001 Dec;16(12):2697-704
references: 11726598
references: Int J Androl. 2002 Aug;25(4):243-52
references: 12121574
references: Environ Health Perspect. 2003 Apr;111(4):414-20
references: 12676592
references: Epidemiology. 2003 May;14(3):278-86
references: 12859027
references: Hum Reprod. 2004 Dec;19(12):2831-7
references: 15459173
references: Int J Androl. 2005 Aug;28(4):208-14
references: 16048632
references: Int J Androl. 1996 Feb;19(1):11-7
references: 8698532
references: Hum Reprod. 2011 May;26(5):1012-6
references: 21382832
references: Int J Androl. 2011 Aug;34(4 Pt 2):e37-48
references: 21366607
references: J Clin Endocrinol Metab. 1999 Oct;84(10):3666-72
references: 10523012
references: Hum Reprod. 2002 Feb;17(2):503-15
references: 11821304
references: Hum Reprod. 2009 Feb;24(2):459-69
references: 19049989
references: N Engl J Med. 2001 Nov 8;345(19):1388-93
references: 11794171
references: Fertil Steril. 1996 May;65(5):1009-14
references: 8612826
references: J Androl. 2001 Jan-Feb;22(1):40-4
references: 11191086
references: Hum Reprod. 2011 May;26(5):1000-11
references: 21335416
references: Am J Epidemiol. 2004 Jan 1;159(1):49-58
references: 14693659
references: Hum Reprod. 2007 Feb;22(2):477-84
references: 17023488
references: J Androl. 2007 Jan-Feb;28(1):1-4
references: 16957135
references: Fertil Steril. 2010 Nov;94(6):2128-34
references: 20149358
references: Int J Androl. 2008 Apr;31(2):93-102
references: 18315714
references: Int J Androl. 2012 Feb;35(1):1-10
references: 21332503
references: Hum Reprod. 2002 Aug;17(8):2199-208
references: 12151459
references: Hum Reprod. 2004 Dec;19(12):2838-44
references: 15388680
references: Hum Reprod. 1990 Jul;5(5):586-92
references: 2394790
references: Int J Androl. 1997 Aug;20(4):201-8
references: 9401822
references: Int J Androl. 2006 Feb;29(1):54-61; discussion 105-8
references: 16466524
references: Contraception. 2002 May;65(5):365-8
references: 12057790
references: BMJ Open. 2013 Jan 25;3(1):
references: 23355656
references: Lancet. 1998 Oct 10;352(9135):1172-7
references: 9777833