BBC News, Anna-Marie
Lever, Health reporter, 5 December 2012
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Chemicals, diet and lifestyle may lower sperm count |
The sperm
count of French men fell by a third between 1989 and 2005, a study suggests.
The semen
of more than 26,600 French men was tested in the study, reported in the journal
Human Reproduction.
The number
of millions of spermatozoa per millilitre fell by 32.3%, a rate of about 1.9% a
year. And the percentage of normally shaped sperm fell by 33.4%.
The average
sperm count remained within the fertile range, but experts want to see more
research into possible causes.
One of the
paper's authors, Dr Joelle Le Moal, an environmental health epidemiologist,
said: "To our knowledge, this is the first study concluding a severe and
general decrease in sperm concentration and morphology at the scale of a whole
country over a substantial period.
"This
constitutes a serious public health warning."
But Dr
Allan Pacey, senior lecturer in andrology at the University of Sheffield, said:
"The change in sperm concentration described, 73.6 to 49.9 million per
millilitre [on average for a 35-year-old], is still well within the normal
range and above the lower threshold of concern used by doctors which is
suggestive of male infertility, 15 million per millilitre."
There has
much been much debate in the past 20 years over whether sperm quality has
decreased, with research supporting both sides of the controversy. This latest
research adds weight to the numerous European studies that suggest one in five
young men has a sperm count low enough to impair fertility.
Prof
Richard Sharpe, from the University of Edinburgh, said: "Something in our
modern lifestyle, diet or environment like chemical exposure, is causing this.
"We
still do not know which are the most important factors, but perhaps the most
likely is a combination, a double whammy of changes, such as a high-fat diet
combined with increased environmental chemical exposures."
The study
analysed data from the French database Fivnat, which logs information from 126
assisted reproduction centres. Researchers examined semen samples provided by
men aged between 18-70 whose partner's were undergoing fertility treatment
because of blocked or missing fallopian tubes.
'Jury out'
As the
study took place over a period of years, it is important that methods remained
the same for comparison- but critics have questioned this.
Dr Pacey
said: "In the paper, the authors claim that the methods for measurement of
sperm concentration and motility 'have not changed noticeably during the study
period', yet to me this is an odd thing to say as in my experience they have
changed remarkably everywhere else in the world.
"I
would argue that the 'jury is still out' on this issue."
While the
study took into account factors that can affect sperm quality, such as age,
researchers were unable to control for socio-economic factors, smoking or
weight, which have been shown to have a major impact.
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