Abstract
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 language | English (US) |
---|---|
Pages (from-to) | 1103-1108 |
Number of pages | 6 |
Journal | Fertility and sterility |
Volume | 67 |
Issue number | 6 |
DOIs | |
State | Published - Jun 1997 |
Keywords
- Mean sperm counts
- Meta-analysis
- Statistical modeling
ASJC Scopus subject areas
- Reproductive Medicine
- Obstetrics and Gynecology