He says the latest research shows that the proportion of men with high sperm counts is declining, while the number of men with low counts is rising. And it's not just sperm counts, he says, but testosterone levels too – that hallmark hormone of manhood.
“It's declined, independent of age, on both sides of the Atlantic,” Dr. Sharpe says. This could be due to the increase in obesity, he says, since abdominal fat can lower testosterone levels, or to conditions when a male fetus develops in the womb – one of the few areas of consensus in sperm studies today.
A woman's diet, lifestyle and environmental exposures, particularly in the early months of her pregnancy as male sex organs are forming, can have a major impact on the man her baby boy will grow up to be.
This is good news, Dr. Sharpe says. “It suggests the low-sperm-count trend is preventable.” And in his opinion the need is urgent. “Men who have low sperm counts also tend to have more abnormal sperm,” and if they make few sperm to begin with, and they delay having children and fertility declines with age, “there's not a lot of room to manoeuvre,” he says.
But Dr. Lamb doesn't see the urgency. “If it was something terribly dramatic already, you should see evidence of it in infertility rates – and the incidence of that has not increased,” she says. “In most Western countries, it hovers around 15 to 17 per cent of couples of reproductive age.”
The number of people seeking infertility treatments has risen, she adds, but that's a reflection of the fact that it has become more socially acceptable to do so, and that more treatments are available.
“It's still an important hypothesis that sperm counts are falling,” she says. “But there's no strong data, rigorously controlled, to suggest that men are at huge risk right now of becoming sterile.”
Meanwhile, one of the more rigorous studies under way has crashed into controversy. A few years after the Danish study appeared, Dr. Skakkebaek and his team began an ambitious project to track sperm counts not by looking back at dubious data, but by looking forward. They began following 5,000 18-year-olds bound for the military, taking detailed histories and sperm samples year after year.
This spring, they sent a confidential interim report to the National Board of Health, showing they had found no decline in sperm counts over the past 15 years. Without the researchers' prior knowledge or permission, the board posted the report on its public website and refused to take it down. Another research team then analyzed the data in the journal Epidemiology.
It was billed as optimistic news, though it still carried a note of caution, warning that “it may be too early for society to dismiss the concerns” depicted in Children of Men.
Dr. Skakkebaek and his team faulted the other researchers for drawing misleading conclusions from the raw and incomplete data, which they said should have run at least 20 years to be remotely comparable with the older study's 50-year range.
Yet Peter Saugmann-Jensen, an official with the Danish health board, said the agency felt compelled to publicize the interim finding, given the widespread anxiety, especially in Denmark, over sperm.
He told the journal Science in June that the board “had concerns about a negative stamp being put on a whole generation of men,” pointing out a Slate.com article that dubbed Danish men “Little Princes of Denmark.”
Before the board released the research, an official visited the sperm bank in Aarhus. He wanted to know if Mr. Schou, who has operated Cryos since 1987, had noticed any decline in semen.
“We told him we hadn't seen any decline, and he was glad to hear it,” Mr. Schou says. “We're not about to be a dying species here. We're doing quite well.”
Carolyn Abraham is The Globe and Mail's medical reporter.