Have human sperm counts really decreased in the past 50 years?
Comment, November 25 2008
Reports are currently appearing in the media alleging that sperm
counts have decreased in the past half century by as much as 50%.
This speculation has largely originated from a research study
carried out in 1992[1].
There has also been speculation that exposure to phthalate
plasticisers may have contributed to such a decline.
However, the 1992 study has subsequently been criticised by a
number of other scientists. Whilst all agree that further research
needs to be conducted, they question whether the findings are
true.
The European Council for Plasticisers and Intermediates (ECPI)
therefore believes that speculation about falling sperm counts, and
particularly about alleged connections with phthalates, should be
treated with great caution.
In 2005, the scientific journal Epidemiology reported that contrary
to previous reports, everyday exposure to phthalates may not have
harmful effects on fertility in young men. In fact, the study
conducted by Dr. Bosse A. G. Jonsson from Lund University Hospital,
Sweden, even showed that exposure to phthalic acid seemed to be
associated with improved reproductive function.
Two other studies, Adverse trends in male reproductive health: we
may have reached a crucial 'tipping point'[2], and Semen quality and male reproductive
health: the controversy about human sperm concentration
decline[3], both question whether the data used for
the 1992 research should be relied upon because it came from
various different studies, all conducted in different ways and
using different methods. They also point out that the results could
have been influenced by a number of factors which were not
recorded.
One of the observations in the report published on the 2008 trends
study was that sperm concentration can be “drastically
reduced” without affecting either time-to-pregnancy or
fertility rates.
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