The question of declining sperm density revisited: an analysis of 101 studies published 1934-1996.
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The average decline in sperm count was virtually unchanged from that reported previously by Carlsen et al. and that the observed trends previously reported for 1938-1990 are also seen in data from 1934-1996.Abstract:
In 1992 Carlsen et al. reported a significant global decline in sperm density between 1938 and 1990 [Evidence for Decreasing Quality of Semen during Last 50 Years. Br Med J 305:609-613 (1992)]. We subsequently published a reanalysis of the studies included by Carlsen et al. [Swan et al. Have Sperm Densities Declined? A Reanalysis of Global Trend Data. Environ Health Perspect 105:1228-1232 (1997)]. In that analysis we found significant declines in sperm density in the United States and Europe/Australia after controlling for abstinence time, age, percent of men with proven fertility, and specimen collection method. The declines in sperm density in the United States (approximately 1.5%/year) and Europe/Australia (approximately 3%/year) were somewhat greater than the average decline reported by Carlsen et al. (approximately 1%/year). However, we found no decline in sperm density in non-Western countries, for which data were very limited. In the current study, we used similar methods to analyze an expanded set of studies. We added 47 English language studies published in 1934-1996 to those we had analyzed previously. The average decline in sperm count was virtually unchanged from that reported previously by Carlsen et al. (slope = -0.94 vs. -0.93). The slopes in the three geographic groupings were also similar to those we reported earlier. In North America, the slope was somewhat less than the slope we had found for the United States (slope = -0.80; 95% confidence interval (CI), -1.37--0.24). Similarly, the decline in Europe (slope = -2.35; CI, -3.66--1.05) was somewhat less than reported previously. As before, studies from other countries showed no trend (slope = -0.21; CI, -2.30-1.88). These results are consistent with those of Carlsen et al. and our previous results, suggesting that the reported trends are not dependent on the particular studies included by Carlsen et al. and that the observed trends previously reported for 1938-1990 are also seen in data from 1934-1996.read more
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References
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Evidence for decreasing quality of semen during past 50 years.
TL;DR: There has been a genuine decline in semen quality over the past 50 years, and as male fertility is to some extent correlated with sperm count the results may reflect an overall reduction in male fertility.
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TL;DR: This laboratory manual consists of 2 sections which describe methods of examination of human semen and semen-cervical mucus interaction in order to standardize procedures and facilitate evaluation and comparison of research reports.
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Are oestrogens involved in falling sperm counts and disorders of the male reproductive tract
TL;DR: It is argued that the increasing incidence of reproductive abnormalities in the human male may be related to increased oestrogen exposure in utero, and mechanisms by which this exposure could occur are identified.
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Male reproductive health and environmental xenoestrogens
Jorma Toppari,John Chr. Larsen,Peter Christiansen,Aleksander Giwercman,Philippe Grandjean,Louis J. Guillette,Bernard Jégou,Tina Kold Jensen,Pierre Jouannet,Niels Keiding,Henrik Leffers,John A. McLachlan,Otto A. Meyer,Jørn Müller,E. Rajpert-De Meyts,Thomas H. Scheike,Richard M. Sharpe,John P. Sumpter,Niels E. Skakkebæk +18 more
TL;DR: The growing number of reports demonstrating that common environmental contaminants and natural factors possess estrogenic activity presents the working hypothesis that the adverse trends in male reproductive health may be, at least in part, associated with exposure to estrogenic or other hormonally active environmental chemicals during fetal and childhood development.
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Decline in Semen Quality among Fertile Men in Paris during the Past 20 Years
TL;DR: The volume of seminal fluid, the sperm concentration, and the percentages of motile and morphologically normal spermatozoa in 1351 healthy fertile men from 1973 through 1992 were measured.
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