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The quality of New Zealand men's sperm has halved in two decades - the most dramatic drop of any Western country.
New research presented to a gathering of international fertility researchers in Brisbane yesterday was told that the sperm volume carried by the average New Zealand man decreased from about 110 million to 50 million per millilitre between 1987 and 2007.
"It's rather dramatic indeed, and one of the largest seen in studies in other parts of the world," said lead researcher Dr John Peek, of Fertility Associates, Auckland.
He said the fall represented a drop from very good to good sperm quality. But if the downward trend continued towards the 20 million "danger mark, we would definitely be running into trouble".
The findings, to be published in the New Zealand Medical Journal, are based on sperm quality data from men volunteering as mystery sperm donors. The biggest drop was seen in the first decade, with a slower decline in recent years.
This contrasts with Australia and the United States, where no decline has been seen. Studies from Scotland and France show marginal declines.
Dr Peek said there were two broad theories on sperm quality decline, one being that semen was affected by environmental toxins, diet and modern changes in lifestyle. "The other is that it is a consequence of what happened when the guy was a baby in the womb."
Professor Rob McLachlan of Melbourne, director of Andrology Australia, which provides education about male reproductive health disorders, said any trend was likely to be global.
"Global trends are differing so we don't have a clear picture on this yet.
"New Zealand is unlikely to have a different situation unless," he joked, "you consider all the fertile New Zealand men may be heading over here."
- AAP
