The question of declining sperm density revisited: an analysis of 101 studies published 1934-1996.

By S. Swan, E. Elkin, L. Fenster. Environmental Health Perspectives, 2000

764 citations recorded by the source corpus.

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.

Subfields: Public Health, Environmental and Occupational Health, Reproductive Medicine

View Paper: https://www.semanticscholar.org/paper/f883058234735403d8ff595165abf6bf01be70df

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Citations in the corpus

Interactions between Exposure to Environmental Polycyclic Aromatic Hydrocarbons and DNA Repair Gene Polymorphisms on Bulky DNA Adducts in Human Sperm (2010, neutral): “Over the last two decades, there has been a growing concern regarding the progressive decline in male fertility [1,2].”
Fertility and infertility: Definition and epidemiology. (2018, background): “[89] found significant declines in sperm density in North America and Europe after controlling for abstinence time, age, percent of men with proven fertility, and specimen collection method.”
Men at risk: occupation and male infertility. (2004, background): “This is not seen in men from non-Western countries (3).”
Trends of male factor infertility, an important cause of infertility: A review of literature (2015, background): “[44] In 2000, an updated comprehensive meta‐analysis was done, which also confirmed the falling trend in sperm count.[58] Also, an another meta‐analysis reported that sperm density has decreased globally by about 50% over the past 50– 60 years.”
The pros and cons of phytoestrogens (2010, neutral): “Among men, sperm counts in the United States and Europe appear to have declined by roughly half over the past 50 years [270].”
Temporal trends in sperm count: a systematic review and meta-regression analysis (2017, methodology): “This controversy has continued unabated both because of the importance of the question and limitations in studies that have attempted to address it (Swan et al., 2000; Safe, 2013; Te Velde and Bonde, 2013).”