title: Effects of male age on semen quality and fertility: a review of the literature.
abstract: OBJECTIVE
  To review the literature on the association between male age and semen quality (semen volume, concentration, motility, and morphology) and fertility status (pregnancy rate and time to pregnancy/subfecundity).
  
  
  METHODS
  Review of English language-published research over the last 20 years from January 1, 1980, through December 31, 1999, using MEDLINE and Biosis databases. Studies with insufficient numbers of subjects, case reports, case series, or anecdotal data were excluded.
  
  
  RESULTS
  Among the methodologically stronger studies, decreases in semen volume of 3%-22%, decreases in sperm motility of 3%-37%, and decreases in percent normal sperm of 4%-18% were likely when comparing 30-year-old men to 50-year-old men. Most studies examining fertility status suggest a relationship between male age and fertility, but the results are most likely confounded by female partner age. Among studies that did control for female age, comparisons between men under 30 and men over 50 found relative decreases in pregnancy rates between 23% and 38%. A comparison of the various age categories showed that the increased risks for subfecundity ranged from 11% to 250%.
  
  
  CONCLUSIONS
  The weight of the evidence suggests that increased male age is associated with a decline in semen volume, sperm motility, and sperm morphology but not with sperm concentration.
authors.affiliation: School of Public Health, University of California, Berkeley, California, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Kidd
authors.forename: B
authors.initials: B
authors.lastname: Eskenazi
authors.forename: A J
authors.initials: AJ
authors.lastname: Wyrobek
mesh_terms: D000328:Adult; D000375:Aging; D005260:Female; D005298:Fertility; D006801:Humans; D016239:MEDLINE; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D012661:Semen / Q000502:physiology*; D013076:Sperm Count; D013081:Sperm Motility; D013094:Spermatozoa / Q000002:abnormalities / Q000502:physiology; D013997:Time Factors