Counting Sperm

"I tried counting mine once, but I went blind with exhaustion," tweeted one reader of the BBC website after it reported that sperm counts were down by half in the past 40 years all over the developed world. And it's true: they are hard to count. The little buggers just won't stay still.

The report, published by Human Reproduction Update on Tuesday, is the work of Israeli, American, Danish, Spanish and Brazilian researchers who reviewed almost 200 studies done in different places and times since 1973. It's called "Temporal trends in sperm count: a systematic review and meta-regression analysis", and the authors are working very hard to get the world's attention.

Dr. Hagai Levine, the lead researcher, told the BBC that if the trend continued humans would become extinct. "If we will not change the ways that we are living and the environment and the chemicals that we are exposed to, I am very worried about what will happen in the future," he said. "Eventually we may have a problem with reproduction in general, and it may be the extinction of the human species."

I think I've seen this movie a few times already. There was "Children of Men", and then "The Handmaid's Tale", and I was even in a sperm-count movie myself thirty years ago. (It was a would-be comedy called ""The Last Straw", but happily it isn't available online.)

Among the many varieties of end-of-the-world stories we like to tell ourselves, the infertility apocalypse is the least violent, and therefore (in good hands) the most interesting in human terms. But the sperm crisis really isn't here yet, or even looming on the horizon.

What the scientists did in the meta-regression analysis was very useful from a general public health point of view. There have been many estimates of what is happening to sperm counts, but they are conducted under different circumstances, usually with fairly small groups of people, and often in clinics that are treating couples with infertility problems.

This big review of the existing research did no new work, but it did extract rather more reliable data from the many studies that have been conducted by other groups, and there definitely is something going on. Compared to 1970s, sperm counts now in the predominantly white developed countries (North America, Europe, Australia and New Zealand) are between 50% and 60% down now.

It has been a fairly steady decline in those places, and and it is continuing in the present, but no such fall has been found in the sperm counts in South America, Africa and Asia. So maybe it's just whites going extinct.

Probably not, though. Most people in South America are white, but there has been no fall in sperm counts there. And there's no separate data in the survey about what's happening in the heavily industrialised Asian consumer societies like Japan, Korea, China and Taiwan, but one suspects that there have been declines in sperm counts there. It's almost certainly an environmental, dietary or lifestyle effect, and therefore probably reversible.

As to which of these possible causes it might be, the jury is still out, but a 2012 study by researchers at the Universities of Sheffield and Manchester concluded that smoking, drinking alcohol, recreational drug use and obesity had little or no effect on sperm counts. Other reports, however, have suggested that eating saturated fats, riding bicycles, watching too much television and wearing tight underpants do adversely effect sperm counts.

In any case, there's no immediate cause for panic, because all of the studies showed that sperm counts, though lower than in the 1970s in some parts of the world, are not "sub-fertile" anywhere. They are still well within the normal range, just lower on average than they used to be. There's no shortage of human beings at present, and there's lots of time to sort this out.

It will almost certainly turn out, when more research has been done, that the main cause of reduced sperm counts is the presence of various man-made chemicals in the environment. Not just one or two chemicals, but more likely a cocktail of different ones that collectively impose a burden on the normal functioning of human metabolism.

We are breathing and ingesting a lot of toxins, and have been since shortly after the rise of civilisation (lead-lined water pipes, etc.). The sheer volume of visible pollutants (particulate matter, etc.) has probably peaked and begun to decline in the most developed countries, but the variety of new chemicals in the environment continues to rise. Further nasty surprises probably lie in wait for us.

Unfortunately, that's the way human beings work: ignore the problem or put up with it until it becomes unbearable, and only then do something about it. It's a strategy that has served us well enough in the past, but will do us increasing damage as the problems become more complex. It's very unlikely, however, that falling sperm counts will be the one that finally gets us.