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Daily News Blog

18
Nov

Sperm Count Documented To Be in Substantial and Persistent Decline

(Beyond Pesticides, November 18, 2022) A new meta-analysis, from researchers at Mount Sinai Medical Center, Hebrew University of Jerusalem, and the University of Copenhagen, among others, finds that the drop in global sperm count is accelerating and the problem has become global. The study shows that sperm count (until this study measured largely in North America, Europe, and Australia) has dropped by 51.6% from 1973 through 2018, and that the rate of decline is gaining speed worldwide. 

A primary culprit, among a plexus of factors, is widespread exposure to toxic chemicals, including pesticides, in the environment. Beyond the implications for individuals and families, this global decline in sperm counts has the potential for population-level impacts and, according to Dr. Shanna Swan, an expert environmental–reproductive epidemiologist, could mean that “in the coming decades, large swaths of the global population of men could be subfertile or infertile.” Beyond Pesticides has long highlighted the relationship between reproductive anomalies and toxic pesticides, particularly the role of endocrine-disrupting (ED) compounds. Most recently, we covered a meta-study on pesticides and fertility that “finds exposure associated with lower semen quality, DNA fragmentation, and chromosomal abnormalities.” The new study is covered in Environmental Health News (EHN).

From 1972 to the present, the count dropped by approximately 1% per year; since 2000, that rate has accelerated to more than 2.6% annually. A 2017 study by the same team showed a decline, between 1973 and 2011, of 28.5% across North America, Europe, Australia, and parts of Asia. This 2022 analysis added data, from another 38 studies, that provide further evidence that the rate of decline has picked up substantially in the past decade.

Average global sperm concentration, the research team found, was 49 million per milliliter of semen in 2018. Dr. Swan pointed out that when sperm count drops below roughly 45 million per milliliter, the ability to cause a pregnancy begins to plummet dramatically. She warned that the future of reproduction could change markedly, with many, many men potentially requiring assisted reproduction techniques, such as IVF (in vitro fertilization), hormone treatment, or intracytoplasmic sperm injection (a technique in which sperm are injected directly into an egg). It is worth noting that the burden of male infertility will, and may already, almost certainly fall most heavily on low-income populations, who may have less access to high-quality healthcare, and less financial ability to pursue assisted reproduction.

The comments of Dr. Swan, one of the paper’s coauthors and a reproductive epidemiologist at Mt. Sinai Medical Center, and of Dr. Hagai Levine, paper co-author and epidemiologist at Hebrew University of Jerusalem, complement one another. Dr. Levine’s: “We have clear evidence that there is a crisis in male reproduction,” is followed by Dr. Swan’s: “It’s really alarming.”

The study did not directly address causes of this phenomenon, per se, but science has recognized for years the significant role that pesticides exposures (especially to endocrine-disrupting ingredients, such as those in diazinon, alachlor, atrazine) likely play in degraded sperm quantity and quality. Other toxic chemicals, such as phthalates, PCBs (polychlorinated biphenyls), and bisphenol A (BPA), can also impair reproductive functions. ED chemicals are ubiquitous — they are found in many industrial products, as well as in consumer products, such as plastics, furniture, clothing, canned food, water bottles, toys, cosmetics, electronics, food packaging, and fertilizers and pesticides. People are exposed through these products, as well as vocationally and dietarily.

Central to many of these chemicals’ impacts on male sperm production (and on reproduction broadly) is endocrine disruption — the disturbance of endocrine function by exposures to an exogenous chemical — that may happen in several ways. Those include mimicking a natural hormone and fooling the body into over-responding to a stimulus, responding at inappropriate times, or blocking the effects of a hormone from certain receptors, and/or directly stimulating or inhibiting the endocrine system, cause over- or under-production of hormones. The National Institutes of Health explainer says that exposures to ED chemicals can cause “deleterious effects on human reproductive health by interfering with the synthesis and mechanism of action of sex hormones. Any change during the synthesis or action of the sex hormones may result in abnormal reproductive functions which includes developmental anomalies in the reproductive tract and decline in semen quality.”

Additional factors influencing sperm quality and quantity include obesity, activity level, diet, stress, smoking, and even climate change (via heat waves, which can reduce sperm quality). Some factors — such as diet and pesticide exposures — are hard to tease apart, given the extent of pesticide residues in the food supply.

To make the epidemiology even more complex, ED chemical exposures during the prenatal “window” during which reproductive organs and traits develop may have a big impact on adult sperm quality. Dr. Swan cited to EHN examples of the magnitude and scope of some ED exposures by noting that “[W]hen a man smokes — a known endocrine-disrupting activity — he lowers his sperm count by about 20%. When a male is born to a woman who smokes, his sperm count is reduced by about 50%. Those effects may last for generations before subsequent children and grandchildren return to normal sperm counts.”

Beyond the reproductive impacts of declining sperm counts, the authors chronicle other aspects of a network of concerns. They note the strong and evidenced association between sperm concentration and increased mortality and morbidity from all causes, and the parallel (to decreasing sperm count) between decline in testosterone and increase in testicular cancer and male genital anomalies.

Commenting on publication of the subject research, Professor Richard Sharpe, of the MRC Centre for Reproductive Health at the University of Edinburgh, noted, “[T]his is desperately bad news for couple fertility, because in our modern world (across the globe) couples are delaying putting their fertility to the test until the female partner is in her 30s–40s, when her fertility . . . is already reduced by 30–60% compared with in her 20s and will continue to decline with her age. . . . [and] recourse to assisted reproduction is unlikely to be of much use as its effectiveness also reduces progressively with age.”

Dr. Channa Jayasena, Reader* in Reproductive Endocrinology at London’s Imperial College, commented, “The [study’s] conclusions fit with a growing narrative that the [health of] average . . . men is declining from reasons such as obesity, reduced exercise, pollution, and environmental chemical exposure.” [*In the United Kingdom and some Commonwealth nations, the title of “Reader” connotes a senior academic with a distinguished international reputation in research or scholarship.]

Dr. Sarah Martins da Silva, Reader in Reproductive Medicine at the University of Dundee, warned, “The conclusion is that sperm counts are falling. The human race is not at immediate risk of extinction, but we really need research to understand why sperm counts are falling and to prevent other unintended implications for male health.” Professor Sharpe added, “Aging societies, such as those across Europe/UK, means that these issues are not just a problem for couples trying to have kids, they are also a HUGE problem for society in the next 50 odd years as less and less young people will be around to work and support the increasing bulge of elderly folk.”

The study authors conclude, “This substantial and persistent decline is now recognized as a significant public health concern. In 2018, a group of leading clinicians and scientists called for governments to acknowledge decreased male fertility as a major public health problem and to recognize the importance of male reproductive health for the survival of the human (and other) species. Research on the causes of this continuing decline and an immediate focused response to prevent further disruption of male reproductive health are needed.”

Nearly every research paper concludes with some version of “more study is needed.” True enough, but Beyond Pesticides notes that “time’s a wasting,” and that action is critical. It is clear that toxic, ED chemicals play a big part in this huge male fertility problem, and that reducing exposures to such compounds is imperative and urgent. Around the world, and here in the U.S., a transition away from chemically intensive agriculture and land management — to organic regenerative practices — would be an enormous and concrete step in addressing the problem. Failing to do so will continue to exacerbate (at least male) infertility, with potentially extreme consequences.

View Dr. Swan’s talk, Modern Life and the Threat to the Future, at Beyond Pesticides 2021 National Pesticides Forum, Cultivating Healthy Communities. Click here.

Learn more about the relationship between pesticide (and other chemical) exposures and the impacts on reproductive health and function; see Beyond Pesticides’ factsheet on pesticides and endocrine disruption, and our Daily News archives on Endocrine Disruption, Infertility, and Reproductive Health.

Sources: https://www.ehn.org/sperm-count-decline-chemicals-2658635273.html and https://academic.oup.com/humupd/advance-article/doi/10.1093/humupd/dmac035/6824414

All unattributed positions and opinions in this piece are those of Beyond Pesticides.

 

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