According to a recently released meta-analysis, sperm counts are decreasing globally and at an accelerated rate due to a class of chemicals known as endocrine disruptors.
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An international team of researchers updated their ground-breaking 2017 study with this article (pdf below), which was published in the journal Human Reproduction Update in November 2022 after reviewing 2,936 academic abstracts and 868 complete articles and analyzing data from 38 sperm count studies conducted on six continents.
According to a 2017 study, sperm counts had decreased by more than 50% over a fifty-year period across North America, Europe, and Australia. This data was updated in the current study, which also included data from South and Central America, Asia, and Africa.
“The aim of this study was to examine trends in sperm count among men from all continents. The broader implications of a global decline in sperm count, the knowledge gaps left unfilled by our prior analysis, and the controversies surrounding this issue warranted an up-to-date meta-analysis,” said the authors.
According to the data, sperm counts decreased on average by 1.16 percent annually between 1972 and 2000, but since then, they have been declining at a rate of 2.64 percent annually.
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The author of the study Shanna Swan summarised the results in an After Skool YouTube video as follows:
“Now we can conclude that among men who didn’t know what their fertility [rate] was, who are, by the way, most representative of the general population, that there was a significant decline [in sperm counts and sperm concentration] in Asia, Africa, and South America—so now we can say that our finding of a significant decline in sperm concentration and count is worldwide—that was a big change from the 2017 paper.
“The other change from the 2017 paper was the rate at which sperm counts are declining: When we look at recent years—particularly since the turn of the century—the rate is 2.64 per year. That’s more than double 1.16, the prior finding.”
The Role of Plastics in Reproductive Disruption
Why the faster rate of decline, is the obvious question.
Swan rejected genetic theories, arguing that while these changes occur in two generations or fewer, genetic alterations “take many generations to appear.”
“That leaves us with the environment,” Swan said.
Swan and other specialists think that a class of chemicals known as endocrine disruptors, which mess with the body’s hormones, is the cause of the issue.
Numerous items that we use on a daily basis include these endocrine disruptors, such as plastic bottles and containers, metal food can liners, detergents, flame retardants, food, toys, ATM receipts, and pesticides.
One prevalent class of these compounds is phthalates, which are frequently found in children’s toys, plastics, and personal care goods. Consumers find it difficult to avoid them, in part because producers are not required to list these chemical substances.
However, a lot of these disruptors take a while to degrade in the environment, which makes them a long-term danger.
Researchers have specific concerns about reproduction since these disruptors can affect fetal maturation and sexual differentiation in the early stages of pregnancy.
Swan demonstrates in the video how these disruptors can prevent the male fetus from producing testosterone as it progresses through development.
“So, here’s the whole picture. There’s the male fetus developing around the first couple weeks of the first trimester: The genetic signal is for the testicles to develop and start making testosterone and here comes this foreign influence from phthalates telling the body, well, you don’t need to make as much testosterone [because] we got it covered as they occupy the spaces … of the androgen receptors, the testosterone receptors.”
“They sit there and they say: Okay we’re good here—you don’t need to make any more [testosterone]. So the body says: Okay—it won’t make any more … and the boy will be under-masculinized.”
Plastics are a component of a broader picture of poisons affecting reproduction across the biosphere, according to Robin Bernhoft, M.D., former president of the American Academy of Environmental Medicine:
“The proliferation of estrogenic chemicals is a major concern. Research has shown that 80 percent of male trout in Colorado had intersex genitalia, a high percentage of male crocodiles in Florida lack penises, and so forth. This is happening on many levels: Direct toxicity from PCBs, direct estrogenic effects from plastics, pesticides, and mercury among other toxins—but also a secondary effect—the stimulation of aromatase, a hormone which then converts testosterone to estrogen independently of the other factors. Pollution in general … stimulates aromatase which then converts available testosterone to estrogen. It is quite scary.”
Criticism of Sperm Count Analysis
Researchers from Harvard’s GenderSci Lab questioned Swan and coworkers’ 2017 study in a paper that was published in the journal Human Fertility in May 2021. The essay challenged the premises and findings of the initial research but did not carry out its own in-depth meta-analysis of sperm investigations.
According to Harvard University professor and director of the GenderSci Lab Sarah S. Richardson, who also teaches scientific history and studies of women, gender, and sexuality, “The extraordinary biological claims of the meta-analysis of sperm count trends and the public attention it continues to garner, raised questions for the GenderSci Lab, which specializes in analyzing bias and hype in the sciences of sex, gender, and reproduction, and in the intersectional study of race, gender, and science,”
The authors contend that “the Sperm Count Biovariability” (SCB), rather than drawing the conclusion that the results support a “Sperm Count Decline” hypothesis:
“SCB asserts that sperm count varies within a wide range, much of which can be considered non-pathological and species-typical. Knowledge about the relationship between individual and population sperm count and life-historical and ecological [i.e., regional] factors is critical to interpreting trends in average sperm counts and their relationships to health and fertility.”
Swan and her coworkers’ meta-analysis, however, did not dismiss the wide range of variances in individual sperm counts, instead looking at dropping overall averages over a longer period of time. It is unclear how regional variance or individual variation based on life-historical circumstances can account for such a sharp overall average drop across all ethnicities.
The Health Consequences of Low Sperm Count
A study in Italy by endocrinologists found that low sperm count was linked to metabolic changes, cardiovascular risk, and low bone mass, according to the lead author Alberto Ferlin, M.D., associate professor of endocrinology at the University of Brescia. This is in contrast to the GenderSci Lab’s science-as-culture analysis.
“Infertile men are likely to have important co-existing health problems or risk factors that can impair quality of life and shorten their lives,” said Ferlin, who is also president of the Italian Society of Andrology and Sexual Medicine. “Fertility evaluation gives men the unique opportunity for health assessment and disease prevention.”
Ferlin and his colleagues discovered that men with low sperm counts were 1.2 times more likely to have higher body fat (larger waistline, higher body mass index, higher blood pressure (systolic, or top reading), higher “bad” (LDL) cholesterol and triglycerides, and lower “good” (HDL) cholesterol) than men with normal sperm counts. About half of the men had low sperm counts.
Last year, fertility research came under fire for failing to account for older studies’ potentially biased sample techniques and revealing that the average sperm count of men worldwide is decreasing at an alarming rate.
Less than 39 million sperm per ejaculate, a standard also used in the US, was considered to be a low sperm count. All the study participants had sperm analysis as part of a thorough health assessment in the university’s fertility clinic, which included involved monitoring their metabolic and reproductive factors.
The researchers also found that they were more likely to have metabolic syndrome, a grouping of these and other metabolic risk factors that raise the risk of getting diabetes, heart disease, and stroke. Men with poor sperm counts also had higher levels of an indicator for insulin resistance, another condition that might result in diabetes.
Read the study given below: