|
A
critique of Acacio et al. Two main concerns:
First,
the measurement technique used by Acacio et al., employing
a Makler chamber, is well known to produce high measures
of sperm count compared to the method most commonly used
(and recommended by WHO). This may explain why the counts
reported in this paper are inconsistent with other recent
sperm count estimates from Los Angeles, which reported much
lower numbers.
For
example, Fisch et
al. reported an average sperm density of 72.7 x
106 /ml among men in Los Angeles who provided prevasectomy
samples, a population with a high proportion of proven fertility.
Paulsen et al.
found a mean sperm density for normal young men in Seattle
in 1990-93 to be 60.2 106 x /ml.
Second,
men coming to a fertility clinic for treatment are not a
representative sample of the population. To gain any insight
into what is happening to normal men, it would be necessary
to find an unbiased sample.
More
generally, even were sperm count data to show that in Los
Angeles there had been no change, this would not invalidate
results from many other areas where sperm counts have been
shown to have declined. The overall picture remains that
on average sperm counts are decreasing globally even if
in some places they are holding steady (or are no longer
declining).
All
that can be concluded from this study is that sperm counts
measured in this highly non-representative group of men
in one clinic, during a recent three-year period, were unaccountably
higher than expected. Studies of national or international
trends in semen quality require a careful examination of
a large number of studies utilizing comparable methods and
populations.
Consider this letter submitted by Dr. Shanna Swan to the
New York Times:
| |
To
the Editor:
The
March 28 Science Times brief, "American Sperm, as
Hardy as Ever," reports that sperm counts don't appear
to be declining in American men and that there may
be no grounds for worry. If only it were that clear-cut.
A
recent study at the University of Southern California
found that the sperm count of men seeking treatment
at fertility clinics was similar to that of men studied
in 1951 and had not decreased, as several other studies
have found. The USC study, contrary to some press
coverage, does not dispute other site-specific studies
that have reported very different results. Nor does
it refute the possibility of a broad average decline
in sperm count. Fertility clinic studies are unreliable
for this sort of study.
Moreover,
sperm counts from the USC study were inconsistent
with the results of several recent studies of sperm
density. And why should the public be concerned one
way or the other? Because reduced sperm counts are
related to decreased fertility, a problem that the
public is clearly concerned about and because these
declines may be caused by significant changes in these
men's environment. For example, recent research finds
that everyday products contain hormone-disrupting
chemicals that may interfere with the reproductive
systems of men and women. This area clearly needs
more research - research that furthers our understanding
rather than confusing the issue.
Shanna
H. Swann, Ph.D.
Research Professor
Family and Community Medicine Medical Sciences Building
University of Missouri
|
|
|
