A meta-analysis of 61 sperm count studies revisited

Stan Becker, Kiros Berhane

Research output: Contribution to journalArticlepeer-review


Objective: To re-examine data on sperm counts over time from 61 studies from around the world. Design: Parametric analyses and flexible nonlinear models of the relation between sperm counts and time. Main Outcome Measure(s): Mean sperm concentrations per milliliter and regression coefficients for possible trends of concentrations over time. Result(s): A significant decline was found only in U.S. studies. Conclusion(s): Studies from specific sites have found declines in sperm counts, but a world-wide decline has not been demonstrated. Rigorous assessment of statistical models should be done before conclusions are drawn. Flexible smoothing models are a useful addition to currently available analytic methods.

Original languageEnglish (US)
Pages (from-to)1103-1108
Number of pages6
JournalFertility and sterility
Issue number6
StatePublished - Jun 1997


  • Mean sperm counts
  • Meta-analysis
  • Statistical modeling

ASJC Scopus subject areas

  • Reproductive Medicine
  • Obstetrics and Gynecology


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