In which the count fell
results of a study published by National Institutes of Health, Bethesda, Maryland, the most prestigious research agency of the us federal government, have confirmed that sperm counts have dropped enormously in the last 60 years in the us and Europe. This is much higher than the findings of any previous studies. The report discloses that sperm counts have fallen at the rate of 1.5 per cent per year in the us since the 1930s. The drop in Europe is twice as steep.
"I hope this study will change the question of concern from 'if there is a decline', to 'why there is a decline'," said Shanna Swan, chief of the reproductive epidemiology section at the California department of health, who is the principal author of the report. "Is the sky falling in? I don't think so.Even though sperm counts have declined, even gone down to about 60 million sperm per millilitre, it's still 60 million. You only need one to make a baby," she said. "But it is a red flag for increasing problems we see in other areas."
Falling sperm counts in the last half century have been associated with higher rates of certain types of cancers of the male reproductive system and a growing number of unusual birth defects. Despite the fall in fertility counts, fertility rates in the us have not been associated with lower sperm counts. As for what is causing the decline, nobody knows for sure. But studies on laboratory animals have linked low sperm counts and reproductive problems to prenatal exposure to certain chemicals. The fall in sperm count could play a role in making people with low sperm counts infertile, Swan said.
The controversy Swan attempts to put to rest started in 1992, when a group of European scientists looked at 61 studies and asserted that from 1938 to 1990, sperm counts around the world dropped from 113 million sperm per millilitre to 66 million sperm per millilitre, a decline of about 1 per cent per year.
But critics of the study attacked it as soon as it was published, blasting the way the study was conducted and asserting that sperm counts had not declined. Other studies with contradictory conclusions were cited. For example, researchers found no drops in sperm count in Seattle. In New York, they found slight increases over the years. In Paris and Denmark, sharp declines were noted. The argument about what was really happening raged on.
"The main problem that has got in the way of really focusing on how to deal with this decline is arguments about methodology and how you analyse the data," said C Alvin Paulsen, author of the Seattle report. "That has sort of blinded people's vision."
So Swan went back to the 1992 study and, taking the criticism into account, reanalysed it. "When I first looked at it, I was sceptical. It had been so widely criticised. I thought it was probably too simple," Swan said. "If the criticism was valid, the decline would have flatten out. So I was extremely surprised that rather than going away, the decline got stronger in the us and Europe."
While the report deals with averages and global trends, Swan is the first to admit that geography may play a far more important role. Sperm counts may fall in one area or in one country and remain constant or even rise in another. The important thing now, she said, is to find out where and why.
"There is definitive evidence that sperm counts are falling in certain areas of the world, but it is not uniform," he said. "But something is going on. The most compelling data resides in fish that and are constantly exposed to contaminants in water." Several studies on wildlife found that in waters contaminated with hormone-disrupting plastics, polychlorinated biphenyls ( pcbs) or other chemicals, some male fish do not develop normal genitalia.
Sperm counts, studies show, are falling in Denmark, but holding constant in Finland. Denmark, too, is showing higher incidence of testicular cancer and certain hormone-related birth defects. Similarly, the Centers for Disease Control, Atlanta, report that testicular cancers, prostate and breast cancers are on the rise in the us. Studies in London have also revealed alarming results.