Uh… About That Sperm Study

Does that new study really show that sperm counts are declining and chemicals are to blame?

Here is the study.

Here is the hysteria as reported in the Washington Post:

Here’s why this study is junk:

• Meta-analysis.. This study is nothing but a meta-anaysis — i.e., a statistical pooling of studies, a “technique” most notoriously used in EPA’s 1992 secondhand smoke railroad. In theory, meta-analysis is a method for combining multiple statistically weak studies into a single statistically stronger study. But the theory only works if the studies are similarly and systematically conducted, as in clinical trials. That is not the case here. This meta-analysis is like combining apples with oranges.
• Component studies are small. The total number of men in the 185 studies making up the meta-anbalysis was 42,935 — i.e., and average study population of 232 men. No study is large enough to stand on its own as signifying anything. These 42,935 men are suppoed to represent billions of men over the past 40 years.
• Selection bias. None of the studies are statistically representative of anything. Study subjects tend to be sperm donors (i.e., self-selected) without any control over health and/or sexual activity.
• No link with chemicals. None of the 185 studies scientifically link chemicals with changes in sperm count.
• Author bias. Study author Shanna Swan is a long-time anti-chemical activist-researcher. Below are couple columns I wrote for FOXNews.com in 2003 debunking her sperm count studies.

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Pesticide-Sperm Count Link Is Impotent
By Steven Milloy
Published June 20, 2003 FOXNews.com

“Scientists for the first time have shown a link between levels of widely used agricultural pesticides in men’s bodies and the number and quality of their sperm,” shrieked USA Today this week.

Steady, USA Today. Underwear, rather than pesticides, is a more probable explanation.

McNews had the wool pulled over its eyes by University of Missouri-Columbia eco-activist researcher Shanna Swan, who has been crusading since the mid-1990s to link pesticides with supposed reduced sperm counts.

The latest chapter in Swan’s crusade began in April when she reported that a small sample of men from Boone County, Mo., had lower sperm quality than similarly small samples of men from Los Angeles, Minneapolis and New York City.

Based on further “analysis,” Swan now reports in a study published in the June 18 Environmental Health Perspectives (search), the 50 Missouri men had higher levels of metabolites of widely used pesticides (alachlor, diazinon, atrazine and others) in their urine than the 50 Minneapolis men.

Swan concluded: “This is the first population-study to demonstrate links between specific biomarkers of environmental exposures and biomarkers of male reproduction in humans. Given the current widespread use of these pesticides, if further study confirms these findings, the implications for public health and agricultural practice could be considerable.”

Doubtful.

In the first place, I’m not quite sure what the dreaded “implications” of Swan’s data are since all men in the study were fertile. They were, in fact, the partners of pregnant women recruited at prenatal clinics.

Secondly, there’s no known biological support for Swan’s idea that pesticides affect sperm quality. Tests do not indicate that alachlor, diazinon and atrazine, for example, produce toxic effects in the reproductive systems of laboratory animals.

A reproductive biologist from the Environmental Protection Agency told USA Today that rodent studies suggest that even the highest pesticide levels found in Swan’s subjects would have been too low to affect sperm quality.

And just because the Missouri men had lower sperm counts and higher pesticide exposure than the Minneapolis men doesn’t automatically mean that pesticides have anything to do with sperm production.

A University of Virginia fertility expert told The Associated Press that he was skeptical of the findings because of the lack of historical documentation of the effect of toxins on sperm.

Sperm counts are known to vary geographically. There is no certain explanation for the phenomenon, although some studies indicate that men in colder regions seem to have higher sperm counts than men in warmer areas.

And it’s really not surprising that men from the agricultural Boone County, Mo., would have more pesticide exposure than an urban area such as Minneapolis.

Swan’s data simply aren’t unexpected and her tenuous conclusions aren’t surprising given her track record of eco-activist, anti-pesticide “research.”

Though anti-pesticide activists have tried for years to link pesticides with declining sperm counts, one key fact stands in their way — there’s no evidence that sperm counts are even declining, much less that pesticides are involved.

In 1999, researchers published in the Journal of Urology a review of all 29 studies from 1938 to 1996 reporting semen analyses of fertile men. They concluded, “there appears to be no significant change in sperm counts in the U.S. during the last 60 years.”

Sperm counts and quality depend on many factors. One that Swan overlooked in her study was the effect of tight-fitting underwear.

In 1996, Dutch researchers reported in the British medical journal The Lancet the results of their study of the effect of underwear on sperm quality and quantity.

They reported that men who wore tight-fitting underwear produced 50 percent less sperm than men who wore loose-fitting underwear. Sperm motility was reduced by two-thirds among the men who wore tight-fitting underwear.

Maybe the Missouri men in Swan’s study wore tighter underwear than their Minneapolis counterparts. I don’t know. Neither does Swan — she didn’t check.

I do know that Swan has absolutely no evidence that implicates pesticides and exculpates all other potential factors. Regardless of the explanation for Swan’s reported observations, sperm quality differences apparently did not affect anyone’s fertility.

Perhaps it’s time for Swan to spend time reconsidering the quality of her crusade.

Steven Milloy is the publisher of JunkScience.com, an adjunct scholar at the Cato Institute and the author ofJunk Science Judo: Self-defense Against Health Scares and Scams (Cato Institute, 2001).

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Sperm Count Beef?
By Steven Milloy
Published April 01, 2007 FOXNews.com

Consumers were frightened this week by media reports about a new study claiming to link mothers’ consumption of beef with reduced sperm counts in their sons ( “Sperm Count Low if Mom Ate Beef, Study Finds” ). But the study amounts to nothing more than a transparent effort to resurrect an already debunked 1990s-era health scare with appalling science and sensational headlines.

From “Mom’s beef puts son’s sperm count at stake” (Los Angeles Times) to “Meaty momma’s boys lose” (Edmonton Sun, Canada) to “Sunday roasts could have hit male fertility” (Daily Mail, U.K.), gullible media around the world once again fell for science-by-press-release committed by longtime environmental activist-researchers.

The supposed findings of the study were that “men whose mothers had eaten more than seven beef meals a week had a sperm concentration that was over 24 percent lower than in men whose mothers ate less beef “and that three times more sons of high-beef consumers had a sperm concentration that would be classified as sub-fertile, according to World Health Organization standards, in comparison to men whose mothers ate less beef.”

But for anyone who makes the effort to look past the press releases touting these findings and to examine the study that supposedly backs them up, these findings fall apart as easily as slow-cooked pot roast.

First, the researchers approached the question of what caused the reduced sperm counts exactly backwards. Rather than investigating all possible causes and eliminating those for which there are no supporting evidence, the researchers, according to their own admission, set out to link maternal beef consumption with fertility problems while ignoring other possible causes.

There are myriad causes of infertility. Focusing on a novel one that might make for good headlines — while overlooking established, but less newsworthy, causes — simply does not constitute bona fide scientific investigation.

Then, of course, none of the men studied seemed to have fertility problems in the first place. In fact, the men had all fathered children. But they were nonetheless targeted by the researchers because “[their] rate of consulting a doctor in the past for possible infertility was significantly higher.”

Simply consulting a fertility specialist, however, does not necessarily indicate that a man has fertility problems.

The researchers’ hypothesis is not that beef itself causes infertility, but rather that the hormone-like medicines and chemicals to which cattle may be exposed are at fault. But even if it were true, for the sake of argument, that hormone-like chemicals were linked with male infertility, the researchers would still be obligated to rule out other potential exposures to these chemicals, such as through other foods or occupational exposures in both the mothers and sons, before blaming beef consumption by mothers.

Although the researchers tout a study size of 387 subjects, only 51 of the sons had mothers who allegedly ate beef more than seven times per week when they were pregnant. So the researchers drew an awfully sweeping conclusion from a minuscule study population.

Moreover, the data on mothers’ beef consumption during 1949 to 1983 were collected by surveying the mothers during 1999 to 2005, as long as 50 years after they were pregnant.

Such self-reported dietary data were not verified by the researchers and are subject to phenomena known in scientific circles as “recall bias” (memory-impaired responses) or “response bias” (intentionally incorrect responses to, say, avoid embarrassing answers). No one really knows what or how much these women actually ate.

It’s also not necessarily true that more frequent beef consumption is greater beef consumption. Someone who consumes four 8-ounce portions of meat per week consumes 14 percent more beef than someone who consumes a 4-ounce portion every day — yet, in this study, the everyday-meat eater is assumed to be the greater consumer of beef.

Although the researchers say in their media release, “We don’t have enough information yet to make any recommendations, and this is not what this study was designed to do,” they then proceed to make dietary recommendations including eating only organic beef and generally reducing beef consumption. This study is about causing alarm, not about sound scientific research.

So just who are these researchers and what’s their real beef?

The University of Rochester’s Shanna Swan and Danish researcher Niels Skakkebaek are well-known to followers of the now-defunct 1990s controversy over hormone-like chemicals in the environment, so-called “endocrine disrupters” or “environmental estrogens.”

Swan, Skakkebaek and others have been trying to scare people that man-made chemicals in the environment and food are reducing fertility, particularly sperm counts. Swan has published 15 related studies since 1997 and Skakkebaek has more than 80 related citations in the scientific literature dating back to 1992.

Despite tremendous media attention, the science of Swan and Skakkebaek has never been particularly persuasive. A National Academy of Sciences committee concluded in 1999 that, “Given the evidence to date, increases in the incidence of male reproductive disorders in humans … cannot be linked to exposures to [hormonally-active agents] found in the environment.”

And since there do not appear to be any sort of worldwide fertility problems that cannot be explained by other causes, it’s no wonder that the endocrine disrupter scare never gained traction.

In addition to the news media’s predilection for scary health stories, who, after all, could pass up a story about hamburgers as intergenerational contraceptives? It unfortunately suffers from an abysmal institutional memory, particularly when it comes to science.

So Swan and Skakkebaek can always count on gullible reporters parroting their “findings” as if they were novel, credible and important, rather than what they really are: stale, unbelievable and meaningless.

Steven Milloy publishes JunkScience.com and CSRWatch.com. He is a junk science expert, an advocate of free enterprise and an adjunct scholar at the Competitive Enterprise Institute.