Men account for at least half of cases. So why have women shouldered the blame?

Male scientists have long written about the contents of their testicles. “Sperm is a drop of brain,” wrote the ancient Greek writer Diogenes Laertius. Leonardo da Vinci drew the penis with a spermatic duct that was directly connected to the spinal cord. 17th-century microscopist Antonie van Leeuwenhoek claimed that every sperm cell contains a folded human, patiently waiting to unfold.

Scientists have been concerned about the seemingly inevitable decline in sperm for almost as long. Most recently, a string of alarming headlines – as well as a new book by a health researcher at Mount Sinai Medical Center in New York – warned that falling sperm counts could threaten the future of humanity. “It’s a global existential crisis,” says Shanna H. Swan, author of Count Down.

Most of these Headlines can be traced back to an influential 2017 meta-analysis by Swan and others that found sperm counts in Europe, North America, Australia, and New Zealand had dropped nearly 60 percent since 1973. The authors reviewed 7,500 sperm count studies from around the world, sorted out most of them, and finally analyzed 185 studies on 43,000 men worldwide.

If you double your sperm count from 100m to 200m, you are not doubling your chances – in fact, it is flattening out, if at all

They called the decline a “canary in a coal mine” for declining male reproductive health around the world. Today the authors would revise this statement. “There is now a clear and present alarm,” says Dr. Hagai Levine, a public health researcher at the Hadassah School of Public Health, Hebrew University and author of the 2017 review. “The canary is in trouble now.” Swan agrees.

Now a group of interdisciplinary researchers from Harvard and the Massachusetts Institute of Technology claim that the fear of an impending Spermageddon has been greatly exaggerated. In one study Published in May in Human Fertility magazine, they reassessed the 2017 review, finding that it was based on flawed assumptions and failed to consider alternative explanations for the apparent decline in sperm.

Sarah Richardson, Harvard Gender and Science Fellow and lead author of the new study, calls the 2017 review’s conclusion “an amazing and terrifying claim that, if true, would justify the apocalyptic tenor of some of the scriptures.” “. Fortunately, she and her co-authors argue, there is little evidence that this is the case.

The 2017 authors were “methodologically rigorous” in screening sperm count studies for quality and consistency, write Richardson and her colleagues. But even the data that passed the pattern were geographically sparse and uneven, and often lacked basic criteria such as the age of the men. In addition, the authors assumed that a single metric – sperm count – was an accurate predictor of male fertility and overall health.

Something that goes on in a man’s body in one month can be completely different from what happens in the next month, and the effects on sperm count could change as well

Nobody knows what an “optimal” sperm count is. The World Health Organization sets a range for the “normal” sperm count of 15 million to 250 million sperm per milliliter. (Men produce around 2 ml to 5 ml per ejaculation.) But it’s not clear whether more is better. Above a certain threshold – according to the WHO 40 million per milliliter – a higher number does not mean that a man is more fertile.

“Doubling your sperm count from 25 million to 50 million doesn’t double your chances,” says Allan Pacey, andrologist at the University of Sheffield in England and editor of Human Fertility. “Doubling from 100 million to 200 million doesn’t double your chances – it flattens out.”

Germaine M. Buck Louis, a reproductive public health researcher at George Mason University in the United States, agrees that sperm count is a poor indicator of fertility. “We don’t see it predict much, especially when it comes to a partner with a healthy female pelvis,” says Buck Louis, who was not involved in the sperm count studies.

The 2017 study authors concluded that lower sperm counts equated to lower fertility – although the declines in sperm count they documented were all in the “normal” range, notes Richardson. “It’s like the whole testosterone discussion – more is better and more is more masculine,” she says. “This is really a point that we stress that there is no known normal or baseline for the average sperm count in the population.”

Sperm count has other limitations than metric. It takes about two months for stem cells in the testes to develop into new sperm, which means each and every count is just a snapshot of a developing landscape.

“Something that goes on in a man’s body in one month can be completely different from what happens in the next month, and the effects on sperm counts could change as well,” says Meredith Reiches, author of the 2021 paper and biological anthropologist at the University of Massachusetts, Boston.

Frozen semen samples: Male infertility accounts for at least half of all infertility cases worldwide. Photo: iStock / Getty

It also overlooks an important piece of the infertility puzzle: women. By focusing only on the male metric, important interactions between sperm, the female reproductive tract, and the egg are omitted. “It’s actually very important to look at the couple,” says Dr. Bradley D. Anawalt, a reproductive endocrinologist with the University of Washington Medical School.

In her book, Swan suggests that sperm counts have decreased primarily due to the rise in endocrine disruptors, a class of hormone-mimicking chemicals found in everything from shampoo to television food packaging. (She also names lifestyle factors like obesity, alcohol, and smoking.)

Richardson and her co-authors suggested an alternative: Perhaps sperm levels rise and fall naturally over time and within populations. The question has not been investigated by reproductive researchers and cannot be easily answered because the world’s sperm counts prior to 1970 are largely unknown.

There are other possible explanations as well. Sperm counting is a tricky business and is known to be prone to human error, says Pacey. (“I’m saying it from the point of view of someone who has spent 30 years counting sperm and knows how difficult it is,” he adds.) In a 2013 review, he noted that counting methods are changing Having improved and standardized since the 1980s, sperm counts seemed to be falling. In other words, it may simply be that previous scientists counted too many sperm.

Swan and Levine agree that research into these alternative hypotheses was important in preventing reproductive health threats. “We showed evidence of a decline and sounded the alarm,” Levine wrote in an email. “We need to investigate the causes, including the unlikely possibility of a non-pathological decline.”

All authors agree on one point: men’s reproductive health is important. And so far it has surprisingly been neglected.

We have built such a medical infrastructure around the fertility and reproductive health of the female body that we missed some of the basic questions about male reproductive health

Male infertility accounts for at least half of all infertility cases worldwide. Historically, however, women have borne most of the blame for the inability to conceive. And with the advent of reproductive technologies like in vitro fertilization, women’s bodies are the ones that are meticulously measured and tracked by reproductive medicine.

As a result, science still lacks a basic understanding of sperm, says Rene Almeling, medical sociologist and author of GUYnecology: The Missing Science of Men’s Reproductive Health.

“We have built such a medical infrastructure around the fertility and reproductive capacity of the female body that we missed some of the fundamental questions about male reproductive health,” says Almeling. “There is just so much basic research on sperm left.”

The key properties of sperm that infertility specialists study today – how many, what shape, and how they swim – haven’t changed in the last 40 years, says Dr. Abraham Morgentaler, urologist and founder of Men’s Health Boston.

Morgentaler, who worked in a semen analysis laboratory at Beth Israel Deaconess Medical Center in Boston in the 1980s, attributes this stagnation to the rise of IVF and other technologies that have become frontline treatments for almost every male fertility problem. “It doesn’t really matter what is wrong with the semen,” he says.

These gaps in knowledge radiate to all bodies. Swan says part of her motivation for writing the book was that she wanted to see men and women become more proactive about their reproductive health.

“It’s invisible,” she says. “People don’t talk about it. They talk about, “Oh, I have high cholesterol” or “My blood pressure is high”. But you would never say, ‘My egg count has gone down’ or ‘My sperm count has gone down’. “

Richardson agrees that the effects of reproductive toxins on fertility deserve further investigation. “To say that we consider these claims to be alarming and apocalyptic claims that are not well founded does not mean that we think this is not an important research agenda,” she says. “There is a need to focus on men’s reproductive health and understand their bodies as reproductive and as environmentally permeable as any other body.” – New York Times

source https://dailyhealthynews.ca/men-account-for-at-least-half-of-cases-so-why-have-women-shouldered-the-blame/