Quality of French men's semen falling
5 December 2012
The concentration of sperm in French men’s semen has been in
steady decline and there has been a decrease in the number of normally
formed sperm, according to a new study published today the journal
Human Reproduction . The researchers say it constitutes a
serious public health warning.
The study is important because, with over 26,600 men involved, it
is probably the largest studied sample in the world and although the
results cannot be extrapolated to other countries, it does support
other studies from elsewhere that show similar drops in semen
concentration and quality in recent years.
The researchers used the French assisted reproduction technology
(ART) database Fivnat, which collected data from 126 main ART
centres in France. They examined semen samples provided by men who
were the partners of women undergoing fertility treatment because
their Fallopian tubes were blocked or missing — in other words, the
couples’ infertility was due to these problems rather than to any
problems with the men’s sperm.
They found that over the 17-year period between 1989 and 2005
there was a significant and continuous 32.2% decrease in semen
concentration (millions of spermatozoa per millilitre of semen), at
a rate of about 1.9% per year. The researchers calculated that in
men of the average age of 35, semen concentrations declined from an
average of 73.6 million/ml in 1989 to 49.9 million/ml in 2005.
Change in sperm shape
In addition, there was a significant 33.4% decrease in the
percentage of normally formed sperm over the same period. Changes in
the way sperm shape (morphology) was measured during this time may
partly explain this decrease and make it difficult to give an
estimate for the general population. However, the researchers say
that these changes do not account for the total decrease in the
quality of sperm morphology observed over the study period.
In their paper, the researchers write: “To our knowledge, it 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. The link with the environment particularly needs to be
One of the authors, Dr Joëlle Le Moal, an environmental health
epidemiologist at the Institut de Veille Sanitaire, Saint Maurice,
France, said: “The decline in semen concentration shown in our study
means that the average values we have for 2005 fall within the
‘fertile’ range for men according the definition of the World Health
Organisation. However, this is just an average, and there were men
in the study who fell beneath the WHO values. The 2005 values are
lower than the 55 million/ml threshold, below which sperm
concentration is expected to influence the time it takes to
The researchers also looked at how well the sperm moved
(motility) and found that the proportion of motile sperm increased
slightly from 49.5% to 53.6% between 1989 and 2005.
Although they made adjustments for variables that could affect
the results, such as the men’s ages, the season, the centre where
they gave their sperm samples, and the technique (standard in vitro
fertilisation or intra-cytoplasmic sperm injection), they were
unable to control for socioeconomic factors, including smoking and
weight, which can affect semen quality and concentration.
Real values may be lower
However, the authors say that, even though ART is equally
accessible to the whole population, it tends to be the better
educated who undergo it in France and they are less likely to smoke
and to be overweight. “Therefore, the real values for sperm
parameters in the general population could be slightly lower than
those that we present and the decreases could possibly be stronger,”
The authors say that there needs to be more research into the
possible causes for the decline in semen concentration and
percentages of normally formed sperm, but other studies have pointed
to the role played by environmental factors such as endocrine
disruptors (chemicals that disturb the body’s normal hormonal
balance). Furthermore, such factors could induce epigenetic changes
(changes in the way genes and cells behave) that might be passed
down the generations, and which could contribute to a longer process
of decline in men’s fertility.
Dr Le Moal said: “Impairments in the quality of human gametes
(male sperm and female eggs) can be considered as critical
biomarkers of effects for environmental stresses, including
endocrine disrupters. Firstly, this is because gametes are the very
first cells from which human beings are built up during their
lifetimes. According to the theories about the developmental origins
of health and diseases, early (foetal, postnatal, but possibly also
preconceptional) exposures may have an impact on adult health; the
testicular dysgenesis syndrome hypothesis could be regarded as an
“Secondly, it has been shown in humans and animals that
intergenerational effects may occur after foetal exposures,
particularly via epigenetic changes. If such exposures and effects
occur in successive generations, accumulated outcomes are plausible.
So the observed trends could be the result of several generations’
For this reason, the authors say they are concerned that there
could be effects on the next generation’s health.
“Our public health warning may help health authorities to
reinforce their actions on endocrine disruptors, hopefully at the
European level, and to sustain research as well as monitoring
systems,” said Dr Le Moal. “We plan to implement a national
monitoring system with the French competent authority (the
Biomedicine Agency), which now runs the national registry of ART.
Our example could help other countries to implement their own
systems. International monitoring systems could be a good idea to
understand what is happening on human reproductive outcomes around
the world, and evaluate public health actions in future,” she
1. M. Rolland, J. Le Moal, V. Wagner, D. Royère, and J. De Mouzon.
Decline in semen concentration and morphology in a sample of 26 609
men close to general population between 1989 and 2005 in France.
Human Reproduction. doi:10.1093/humrep/des415