Evidence for decreasing quality of semen during past 50 years

In a 1981 study, 80% of the DES-exposed males qualified as infertile

1992 Study Abstract

OBJECTIVE
To investigate whether semen quality has changed during the past 50 years.

DESIGN
Review of publications on semen quality in men without a history of infertility selected by means of Cumulated Index Medicus and Current List (1930-1965) and MEDLINE Silver Platter database (1966-August 1991).

SUBJECTS
14,947 men included in a total of 61 papers published between 1938 and 1991.

MAIN OUTCOME MEASURES
Mean sperm density and mean seminal volume.

RESULTS
Linear regression of data weighted by number of men in each study showed a significant decrease in mean sperm count from 113 x 10(6)/ml in 1940 to 66 x 10(6)/ml in 1990 (p < 0.0001) and in seminal volume from 3.40 ml to 2.75 ml (p = 0.027), indicating an even more pronounced decrease in sperm production than expressed by the decline in sperm density.

CONCLUSIONS
There has been a genuine decline in semen quality over the past 50 years. As male fertility is to some extent correlated with sperm count the results may reflect an overall reduction in male fertility. The biological significance of these changes is emphasised by a concomitant increase in the incidence of genitourinary abnormalities such as testicular cancer and possibly also cryptorchidism and hypospadias, suggesting a growing impact of factors with serious effects on male gonadal function.

Such remarkable changes in semen quality and the occurrence of genitourinary abnormalities over a relatively short period is more probably due to environmental rather than genetic factors. Some common prenatal influences could be responsible both for the decline in sperm density and for the increase in cancer of the testis, hypospadias, and cryptorchidism. Whether oestrogens or compounds with oestrogen-like activity or other environmental or endogenous factors damage testicular function remains to be determined.

Sources:

  • Full text (free access) : Evidence for decreasing quality of semen during past 50 years, The International journal of risk & safety in medicine, The BMJ, bmj00091-0019, PMCID: PMC1883354, 1992 Sep 12.
  • Featured image credit freemalaysiatoday.
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