Reports of falling sperm counts and testosterone levels have fuelled fears over chemicals, pollution and modern lifestyles. But how much do
... But how much do scientists agree on what is affecting male fertility? The world is unwittingly walking into a male reproductive crisis, scientists warned this week as they presented data that revealed an apparent halving of average male testosterone levels over the past 50 years. āIt is mind-blowing that testosterone has declined by 50%,ā Prof Hagai Levine, who led the work, told the Guardian. āThis is a lot. Wake up people. Wake up.ā The finding is the latest in a series of recent results that suggest male fertility is in crisis. Levineās team has previously documented an apparent drastic decline in global sperm counts, in what has come to be known as the āspermageddonā paper. The issue has become a preoccupation across the political spectrum. The US health secretary, Robert F Kennedy Jr, has called declining sperm counts an āexistential crisisā and Levineās work has been seized on in the āmanosphereā as proof modern society is emasculating men. The findings have also galvanised concerns about the hazardous impact of endocrine-disrupting chemicals, air pollution and global heating on human health. Among scientists, though, the trend is disputed. While Levine and colleagues have embraced the doomsday narrative ā his American co-author, Prof Shanna Swan, has suggested that sperm counts could hit zero by 2045 ā others are highly sceptical. Prof Allan Pacey, a professor of andrology at the University of Manchester, is among them. āThereās a tendency to pick the data that supports our viewpoint,ā said Pacey. āFor those who think the world is going to hell in a handcart and weāre all doomed, testosterone and sperm count decline make sense.ā In a more recent analysis of sperm count trajectories, using arguably more consistent measurement techniques, Paceyās group found no evidence of a substantial decline (sperm quality, however, did appear to be deteriorating). Other attempts to replicate the findings have produced mixed results. āDo I think thereās an issue with male infertility? Yes,ā said Pacey. āBut sperm count decline isnāt one that I worry about.ā
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