Skip to main content
Open access
Research Article
1 October 2000

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

Publication: Environmental Health Perspectives
Volume 108, Issue 10
Pages 961 - 966


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.

Formats available

You can view the full content in the following formats:

Information & Authors


Published In

Environmental Health Perspectives
Volume 108Issue 10October 2000
Pages: 961 - 966
PubMed: 11049816


Published online: 1 October 2000



S H Swan
Family and Community Medicine, University of Missouri, Columbia, Missouri 65212, USA. [email protected]
E P Elkin
Family and Community Medicine, University of Missouri, Columbia, Missouri 65212, USA. [email protected]
L Fenster
Family and Community Medicine, University of Missouri, Columbia, Missouri 65212, USA. [email protected]

Metrics & Citations


About Article Metrics


Download citation

If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click DOWNLOAD.

Cited by

  • Implications of Exposure to Air Pollution on Male Reproduction: The Role of Oxidative Stress, Antioxidants, 10.3390/antiox13010064, 13, 1, (64), (2024).
  • Camel milk or silymarin could improve the negative effects that experimentally produced by aflatoxin B1 on rat’s male reproductive system, BMC Veterinary Research, 10.1186/s12917-024-03965-5, 20, 1, (2024).
  • Occurrence, spatial distribution, risk assessment, and management of environmental estrogens in surface waters of the Taihu basin, Environmental Chemistry, 10.1071/EN23112, 20, 8, (339-353), (2024).
  • Deteriorating Semen Quality: The Role of the Environment, Seminars in Reproductive Medicine, 10.1055/s-0044-1782151, 41, 06, (226-240), (2024).
  • Signatures of metabolic diseases on spermatogenesis and testicular metabolism, Nature Reviews Urology, 10.1038/s41585-024-00866-y, (2024).
  • Adverse effects of exposure to petrol-generator exhaust fumes on the reproductive hormones, testis and spermatozoa in male dogs, Reproductive Toxicology, 10.1016/j.reprotox.2023.108516, 123, (108516), (2024).
  • The Protective Role of Camel Milk against Reprotoxicity, Hepatotoxicity, and Nephrotoxicity in Aflatoxic-Induced Male Rats, Research Journal of Pharmacy and Technology, 10.52711/0974-360X.2023.00179, (1072-1078), (2023).
  • A review of different deep learning techniques for sperm fertility prediction, AIMS Mathematics, 10.3934/math.2023838, 8, 7, (16360-16416), (2023).
  • PUFAs and Their Derivatives as Emerging Players in Diagnostics and Treatment of Male Fertility Disorders, Pharmaceuticals, 10.3390/ph16050723, 16, 5, (723), (2023).
  • Novel Lines of Research on the Environmental and Human Health Impacts of Nut Consumption, Nutrients, 10.3390/nu15040955, 15, 4, (955), (2023).
  • See more

View Options

View options


View PDF

Get Access

Restore your content access

Enter your email address to restore your content access:

Note: This functionality works only for purchases done as a guest. If you already have an account, log in to access the content to which you are entitled.







Copy the content Link

Share on social media