title: Semen quality improves marginally during young adulthood: a longitudinal follow-up study.
abstract: OBJECTIVE
  Does semen quality improve during early adulthood?
  
  
  CONCLUSIONS
  Semen variables change little during the third decade of life, however some improvement in sperm morphology and motility may occur.
  
  
  BACKGROUND
  A suspicion of deteriorating semen quality has been raised in several studies. The longitudinal development of semen quality in early adulthood is insufficiently understood.
  
  
  METHODS
  A longitudinal follow-up of two cohorts of volunteer young adult Finnish men representing the general population was carried out. Cohorts A (discovery cohort, born 1979-1981, n = 336) and B (validation cohort, born 1983, n = 197) were followed up from the age of 19 years onward for 10 years.
  
  
  METHODS
  Inclusion criteria included that both the men and their mothers were born in Finland. Semen analysis was performed in cohorts A and B at 2-4 year intervals over a period of 10 years. Semen volume, sperm concentration, total sperm count, motility, total motile count and morphology were the variables assessed in the analysis. A physical examination was carried out at each visit to detect any significant andrological abnormalities. The overall participation rate was 13.4%.
  
  
  RESULTS
  During the follow-up, the percentage of sperm with normal morphology and the percentage of motile sperm increased significantly both in the discovery (A) (P < 0.001 at 19 versus 29 years for both) and validation (B) (P < 0.001 and P = 0.03 at 19 versus 29 years, respectively) cohort. Sperm concentration and total sperm count showed a significant increase with age only in cohort B (P = 0.03 at 21 versus 29 years, P = 0.009 at 19 versus 29 years, respectively).
  
  
  CONCLUSIONS
  A limited number of men participated both in the first round and in the final fourth round (cohort A, n = 111 and cohort B, n = 90 men) and in all four rounds (cohort A, n = 61 and cohort B, n = 52).
  
  
  CONCLUSIONS
  Almost full spermatogenic capacity is reached by the age of 19 years. However, the improvement in sperm motility and morphology during early adulthood may slightly improve male fecundity.
  
  
  BACKGROUND
  This study was supported by the European Commission (QLK4-CT-1999-01422, QLK4-CT-2001-00269, QLK4-2002-0063, FP7/2008-2012: DEER 212844), The Danish Medical Research Council (9700833, 9700909), Danish Agency for Science (Technology and Innovation 09-067180), the Svend Andersen's Foundation, Velux Foundation, and Novo Nordisk Foundation, the Turku University Hospital, Sigrid Jusélius Foundation and the Academy of Finland. There are no conflicts of interest.
authors.affiliation: Department of Physiology, University of Turku, Turku, Finland Department of Obstetrics and Gynaecology, University of Turku and Turku University Hospital, Turku, Finland antti.perheentupa@utu.fi.
authors.forename: Antti
authors.initials: A
authors.lastname: Perheentupa
authors.affiliation: Department of Physiology, University of Turku, Turku, Finland.
authors.forename: Sergey
authors.initials: S
authors.lastname: Sadov
authors.affiliation: Department of Physiology, University of Turku, Turku, Finland.
authors.forename: Riitta
authors.initials: R
authors.lastname: Rönkä
authors.affiliation: Department of Physiology, University of Turku, Turku, Finland.
authors.forename: Helena E
authors.initials: HE
authors.lastname: Virtanen
authors.affiliation: Department of Physiology, University of Turku, Turku, Finland.
authors.forename: Wiwat
authors.initials: W
authors.lastname: Rodprasert
authors.affiliation: Department of Physiology, University of Turku, Turku, Finland.
authors.forename: Matti
authors.initials: M
authors.lastname: Vierula
authors.affiliation: University Department of Growth and Reproduction, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Jørgensen
authors.affiliation: University Department of Growth and Reproduction, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Niels E
authors.initials: NE
authors.lastname: Skakkebæk
authors.affiliation: Department of Physiology, University of Turku, Turku, Finland Department of Paediatrics, University of Turku and Turku University Hospital, Turku, Finland.
authors.forename: Jorma
authors.initials: J
authors.lastname: Toppari
mesh_terms: D000328:Adult; D000367:Age Factors; D005387:Finland; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D015999:Multivariate Analysis; D060728:Reproductive Health; D055101:Semen Analysis; D013076:Sperm Count; D013081:Sperm Motility; D013091:Spermatogenesis
keywords: cohort; fertility; germ cell; maturation; morphology; motility; reproductive health; sperm; spermatogenesis; testis