Between 1989 and 2005 the sperm count of French men dropped
by a third, according to research.
Compiling data from over 26,000 men, the study is thought to be
the most extensive ever performed. It draws on data collected from French IVF
clinics with researchers testing semen samples provided by men who were partners
of women with diagnosed fertility problems.
In a paper published in the journal Human Reproduction, researchers
note a continuous 32.2 percent decrease in total sperm count with an overall
33.4 percent decrease in healthy sperm.
The researchers say that their results 'constitute a
serious public health warning'. The research will be added to other
evidence that points toward declining male fertility in the industrialised
In the study, for men with average age of 35, semen
concentrations declined from an average of 73.6 million per millilitre in 1989
to 49.9 million per millilitre in 2005.
Co-author Dr JoÃ«lle Le Moal, an environmental health
epidemiologist at the Institut de Veille Sanitaire, Saint Maurice, France, says
that the values for 2005 'fall within the "fertile" range for men
according the definition of the World Health Organisation'.
However, Dr Le Moal continues, 'the 2005 values are lower than the
55 million per millilitre threshold, below which sperm concentration is
expected to influence the time it takes to conceive'.
The findings have been greeted with scepticism by some scientists
who question the study's methodology. The researchers controlled their results
for the effect that age has on semen concentration but not other variables.
Dr Allan Pacey, a senior lecturer in andrology at Sheffield
University and chairman of the British Fertility Society, told the Guardian: 'I
would urge much caution in its interpretation as there remain too many
unknowns. In my view, the paper certainly does not resolve the issue of whether
or not sperm counts have declined or not'.
In particular, Dr Pacey said that the paper claimed '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'.
Accordingly, Dr Pacey suggested, the decrease noted in the paper
might just be 'a function of alterations to laboratory method'.
Professor Richard Sharpe, at the Medical Research Council Centre for Reproductive Health at Edinburgh University, who was not involved in the study,
said he did 'not accept that the basic methods for counting sperm have changed down
the years, so there's no reason why sperm counts should go down unless it is
Professor Sharpe added that the study meant it was 'time for action' and that research should be
undertaken to determine the reasons for the supposed decline in male fertility.
'We still do not know which are the most important
factors', he said, 'but perhaps the most likely is that it is a combination, a
"double whammy", of changes such as a high-fat diet combined with
increased environmental chemical exposures'.