Is humankind really facing “Spermageddon,” a decline in sperm count that could spell the end of the species? Maybe, maybe not. A new paper by researchers from Harvard University, MIT and other top-notch institutions provides an alternative interpretation of the facts cited in a 2017 meta-study, which warned of a drastic 60 percent drop in sperm count in the West during the last 50 years.
The original paper, by Hagai Levine of the Hebrew University-Hadassah School of Public Health and Community Medicine, Shanna Swan and colleagues, said that sperm concentration (the number of sperm per milliliter) had plunged by 52.4 percent in the West.
Sperm count – sperm concentration multiplied by the volume of the sample – had dropped by 59.3 percent from 1973 to date, they found.
The 2017 study inspired apocalyptic headlines the world wide, such as Newsweek’s “Who’s Killing America’s Sperm?” Haaretz went with “Western Men’s Free-falling Sperm Count Is a ‘Titanic Moment for the Human Species.’” We are, many agreed, all but doomed.
To recap, the 2017 meta-study, which the Harvard team itself agrees was the largest and most methodologically rigorous one to date, screened 7,500 sperm-count studies and, after weeding out unsuitable ones, wound up with 185 studies done between 1973 and 2011 on 43,000 men worldwide. Even so, Marion Boulicault of Harvard, Sarah S. Richardson and colleagues, publishing in the journal Human Fertility, suggest weaknesses in the data, such as men’s ages only being known in two-thirds of the cases and other missing crucial information.
And where the original authors see a steep decline in sperm counts in the “West” (consisting of North America, Europe, Australia and New Zealand), Harvard sees natural variability. Though praising the original paper at length for its methodology and impact, they query the definition of "decline," given that there is no definition for optimal sperm count. They also keenly question the grouping of West and non-West, or “other.”
Go non-West, young man
Let’s get the West/other groups out of the way so we can concentrate on male seed.
- Sperm in space: Unlike astronauts, it can survive if frozen
- Moderate marijuana use can raise sperm count, surprising study shows
- Western men's free-falling sperm count is a 'Titanic moment for the human species'
Speaking with Haaretz, Hagai Levine takes the opportunity to correct a popular misconception about the 2017 paper and its grouping of West (sperm in decline) and non-West (sperm ostensibly not in decline), which inspired not a few racists to frantically bang their gongs.
“These groups have used Levine and Swan’s research to argue that the fertility and health of men in whiter nations are in imminent danger, often linking the danger to the perceived increase in ethnic and racial diversity,” the Harvard team points out.
No, Levine explains, he didn’t find decline in the West and no decline or lesser decline in the non-West.
It’s true that the distinction of West and non-West is artificial, but it’s because there have been a lot of studies on sperm counts/concentrations in the “West” but not a lot of studies elsewhere, he explains.
“We have enough data to say there is something significant for Western men, unfortunately. But the amount of studies in the ‘other’ areas, Asia and Africa, was too small to reach clear conclusions. We didn’t reach a conclusion that there is no decline in the non-West – we couldn’t tell! That remains the case,” he says. “But the facts show that in North America and Europe, there is a downtrend.”
The Harvard paper doesn’t contradict the facts, he adds. Indeed, the Harvard team explicitly points out that it’s reinterpreting the data, not arguing them.
“We agree that today there are couples needing infertility treatment – the most basic reproductive act has become dependent on external intervention,” Levine adds.
There is no global statistic for sperm count 50 years ago, 10 years ago or today. So what remains is: what those facts and data indicate.
Stand and be counted
A key argument in the reinterpretation by Boulicault et al is that the studies on which Levine’s paper is based all follow some basic assumptions, implicit and explicit, about how to measure and interpret sperm counts.
These assumptions (to generalize) are problematic scientifically and ethically too, they claim. Moreover, the 2017 paper understandably had an upshot: the “Sperm Count Decline hypothesis, “ which has become all but dogma in the popular press. Shanna Swan even co-authored a book, “Count Down,” with Stacey Colino, warning that the future of the human race is imperiled by the escalating sperm count crisis.
But Boulicault and her colleagues think that what’s being observed could be natural variability. Sperm count varies within a wide range, much of which can be considered non-pathological and species-typical, they argue. Specific studies on sperm count should therefore factor in the relationship between individual and population sperm counts, and historical and ecological factors.
In the stead of the Sperm Count Decline hypothesis, they offer the Sperm Count Biovariability hypothesis.
Also, who says a lower sperm count compared with the ’70s spells greater infertility and poorer overall male health, as Levine and the Israeli-international team contended? Who says the sperm count observed in the ’70s in the “West” was the species’ optimum? Sperm count above a critical threshold “is not necessarily an indicator of better health or higher probability of fertility relative to less,” the Harvard team writes. “The assumption that male fertility scales proportionately with sperm count is unsupported by any available evidence,” they spell out.
OK. A host of separate research has indicated sperm count problems, and other problems such as males with a micropenis, due to endocrine disruptors – chemicals that mimic female hormones, and other pollutants. But the Harvard team doesn’t accept the link between the hormone disruptors in pollution and sperm count as a given cause of the supposed disappearance of Western sperm.
“Sperm count varies across bodies, ecologies, and time periods,” they write, urging that sperm count studies factor in “life-historical” as well as ecological elements.
If anything, Levine applauds the critique. “I welcome that my scientific work is so interesting to the world, and that in this case the critics clearly noted the scientific power of the work I did. There is no argument over the facts,” he told Haaretz. “That’s what meta-analysis does: we presented the facts, and I’m glad they agree with them. Now there’s a matter of interpretation. I’m the first to say that different interpretations are possible, and we noted that there could be different interpretations.”
As an epidemiologist studying disease processes, research is always constrained by the data, Levine explains: “What we always see is like shadows in a cave. We only see the shadows; we don’t do experiments where we could control the circumstances.”
Bottom line, the Harvard group urges that their variability argument, rather than “sperm decline,” is a more suitable basis for pursuing research – and it has the advantage that it would be less likely to trigger the alt-right.
Levine himself points out that people tend to impose metaphors on scientific results. The fact that it made waves all around the world, and various elements took the research and interpreted it as they found it convenient to do so, doesn’t mean he goes there. But, he urges, “We can’t ignore male infertility. Clearly the issue is, often, a tendency to ignore it.”