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