Infertility: Men account for at least half of cases. So why have women shouldered the blame? – The Irish Times

Male scientists have long waxed poetic on the contents of their testes. Sperm is a drop of brain, wrote the ancient Greek writer Diogenes Laertius. Leonardo da Vinci drew the penis with a sperm duct that connected directly to the spinal cord. The 17th-century microscopist Antonie van Leeuwenhoek claimed that each sperm cell contained within it a folded-up human being waiting patiently to unfurl.

For nearly as long, scientists have fretted about sperms seemingly inevitable decline. Most recently, a series of alarming headlines as well as a new book by a public health researcher at Mount Sinai Medical Center in New York warned that falling sperm counts might threaten the future of the human race. Its a global existential crisis, saysShanna H Swan, author of the book Count Down.

Most of these headlines can be traced to an influential 2017 meta-analysis by Swan and others, which found that sperm counts in Europe, North America, Australia and New Zealand had plummeted by nearly 60 per cent since 1973. The authors screened 7,500 sperm-count studies from around the world, weeded out most of them and ultimately analysed 185 studies on 43,000 men worldwide.

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

Now a group of interdisciplinary researchers from Harvard and Massachusetts Institute of Technology contend that fears of an impending Spermageddon have been vastly overstated. In a study published in May in the journal Human Fertility, they re-evaluated the 2017 review and found that it relied on flawed assumptions and failed to consider alternate explanations for the apparent decline of sperm.

Sarah Richardson, a Harvard scholar on gender and science and the senior author ofthe new study, calls the conclusion of the 2017 review an astonishing and terrifying claim that, were it to be true, would justify the apocalyptic tenor of some of the writing. Fortunately, she and her coauthors 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, Richardson and her colleagues write. But even the data that passed muster was geographically sparse and uneven and often lacked basic criteria such as the age of the men. Moreover, its authors took for granted that a single metric sperm count was an accurate predictor of male fertility and overall health.

No one knows what an optimal sperm count is. The World Health Organisation sets a range of normal sperm count as from 15 million to 250 million sperm per millilitre. (Men produce about 2ml to 5ml per ejaculation.) But it isnt clear that more is better. Above a certain threshold 40 million per millilitre, according to the WHO a higher count does not mean a man is more fertile.

Doubling your sperm count from 25 million to 50 million doesnt double your chances, says Allan Pacey, an andrologist at the University of Sheffield, in England, and the editor of Human Fertility. Doubling it from 100 million to 200 million doesnt double your chances in fact it flattens off, if anything.

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 dont see it predicting much of anything, especially in the context of a partner with a healthy female pelvis, says Buck Louis, who was not involved in the sperm-count studies.

The authors of the 2017 study inferred that lower sperm counts equated to lower fertility even though the sperm-count declines they documented all took place within the normal range, Richardson notes. Its similar to the whole conversation around testosterone more is better, and more is manlier, she says. Thats really a point we make, that there is no known normal or baseline for average population sperm counts.

Sperm count has other limitations as a metric. It takes about two months for stem cells in the testes to develop into new sperm, meaning that any single count is merely a snapshot of an evolving landscape.

Something thats going on in a mans body one month may be totally different from whats happening the next month, and the effects on sperm count might be changing also, says Meredith Reiches, an author ofthe 2021 paper and a biological anthropologist at the University of Massachusetts,Boston.

It also overlooks a vital piece of the infertility puzzle: women. Focusing only on the male metric leaves out key interactions between sperm, the female reproductive tract and the egg. Its very important, actually, to look at the couple, says Dr Bradley D Anawalt, a reproductive endocrinologist at the University of Washington school of medicine.

In her book, Swan suggests that sperm counts have plummeted largely because of the rise of endocrine disrupters, a class of hormone-mimicking chemicals found in everything from shampoo to TV-dinner packaging. (She also cites lifestyle factors such as obesity, alcoholand smoking.)

Richardson and her coauthors suggested an alternative: perhaps sperm levels naturally rise and fall over time and within populations. The question has not been explored by reproductive researchers and cannot be answered easily, as global sperm counts before 1970 are largely unknown.

There are other possible explanations, as well. Sperm-counting is a tricky business and notoriously prone to human error, Pacey says. (I say it from the point of view of someone who spent 30 years counting sperm and knows how difficult it is, he adds.) In a 2013 review article, he notes that as methodologies for counting had improved and been standardised since the 1980s, sperm counts had appeared to fall. In other words, it may simply be that earlier scientists were overcounting sperm.

Swan and Levine agree that exploring these alternative hypotheses was important, so that threats to reproductive health could be prevented. We showed evidence for decline, and raised alarm, Levine writes in an email. We need to study the causes, including the unlikely possibility of non-pathological decline.

There is one point that every author agrees on: mens reproductive health matters. And until nowit has been surprisingly neglected.

Male infertility contributes to at least half of all cases of infertility worldwide. Yet, historically, women have shouldered most of the blame for the inability to conceive. And with the rise of reproductive technologies such as in-vitro fertilisation, womens bodies are the ones that have been meticulously measured and tracked by reproductive medicine.

As a result, science still lacks basic knowledge when it comes to sperm, says Rene Almeling, a sociologist of medicine and author of GUYnecology: The Missing Science of Mens Reproductive Health.

We have built up such a medical infrastructure around the fertility and reproductivity of womens bodies that we havent asked some of the basic questions about mens reproductive health, Almeling says. There is just so, so much basic research still to be done about sperm.

The main qualities of sperm that infertility specialists look at nowadays how many, what shape and how they swim have not changed in the past 40 years, says Dr Abraham Morgentaler, a urologist and founder of Mens Health Boston.

Morgentaler, who worked at a semen-analysis lab at Beth Israel Deaconess Medical Center, in Boston, in the 1980s, attributes this stagnation to the rise of IVF and other technologies, which have become frontline treatments for almost any male-factor fertility problem. It almost doesnt even matter whats wrong with the sperm, he says.

These knowledge gaps radiate out 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.

Its invisible, she says. People dont talk about it. You talk about, Oh, Ive got a high cholesterol measure, or My blood pressures up. But you never would say, My egg count is down, or My sperm count is down.

Richardson agrees that the effect of reproductive toxins on fertility deserved further investigation. To say that we think these are alarmist and apocalyptic claims, and theyre not well founded, is not to say that we think it isnt an important research agenda, she says. There is a need to centre on mens reproductive health and understand their bodies as reproductive and as porous to the environment as anyones bodies. New York Times

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Infertility: Men account for at least half of cases. So why have women shouldered the blame? - The Irish Times