Declining sperm counts in the United States? A critical review

Purpose: Recent reports suggest declining sperm counts in the United States . These reports did not include all available data and did not account for geographic variations noted in prior studies, We examined all available dat a on U.S. sperm counts and evaluated whether geographic variations account for the decline suggested. Materials and Methods: We reviewed all 29 U.S. studies from 1938 to 1996 re porting manually counted semen analyses of 9,612 fertile or presumably fert ile men. We determined mean sperm concentrations by geographic location wit h weighted analysis of variance, and assessed any changes with time by line ar regression analysis. Results: Mean sperm concentrations from New York were significantly higher than from all other U.S. cities (98.6 versus 71.6 x 10(6) sperm per cc, res pectively, p = 0.006),There has been no statistically significant change wi th time for mean sperm concentrations reported from New York (p = 0.49) or from U.S. cities other than New York (p = 0.62). Analysis without separatin g by location revealed a decline (p = 0.047). Conclusions: Sperm concentrations are highest in New York compared to other U.S. cities. When accounting for this geographic difference and examining all available data, there appears to be no significant change in sperm coun ts in the U.S. during the last 60 years. Further studies addressing the cau ses of geographic variations are needed.