A new study shows a steady decline in French male sperm count and quality from 1989 to 2005, reflecting evidence that suggests this is a global phenomenon. The researchers call for health authorities to reinforce their action on endocrine disruptors, which have been cited as a possible environmental cause. Reporting their findings in a paper published online first in the journal Human Reproduction on 4 December, the researchers note that as far as they know, this is the first study to find a “severe and general decrease in sperm concentration and morphology at the scale of a whole country over a substantial period”, urging that: “This constitutes a serious public health warning.” They suggest further studies should look for possible environmental causes.

32.2% Drop in Semen Concentration For their research, co-author Joëlle Le Moal, an environmental health epidemiologist at the Institut de Veille Sanitaire, Saint Maurice, and colleagues, used semen analysis data from over 26,600 men attending 126 centers belonging to the French assisted reproduction technology (ART) database Fivnat. Although the semen data came from ART centers, the men themselves were not having treatment: it was their female partners who received treatment, mostly for blocked or missing Fallopian tubes. The researchers found that over the 17 years up to and including 2005, there has been a significant and continuous 32.2% drop in semen concentration, at a steady rate of 1.9% a year. In men of average age 35 years, the semen concentration (or sperm count, the amount of sperm in a volume of semen) fell from an average of 73.6 million per ml in 1989 to 49.9 million per ml in 2005. There was also a significant 33.4% drop in normally-formed sperm over the same period. The authors note that while there have been changes in the way sperm shape (morphology) is measured, they are not enough to explain all of this figure. Nevertheless, they can’t be sure this is representative of the general population. The researchers found there was a slight increase in sperm motility (how well they move). The proportion of motile sperm went up from 49.5% in 1989 to 53.6% in 2005.

Below Threshold that Influences Time to Conceive Le Moal tells the press in a statement that although the the 2005 sperm count level is still within the range the World Health Organization defines as “fertile”, it is “just an average, and there were men in the study who fell beneath the WHO values”. And she points out: “The 2005 values are lower than the 55 million per ml threshold, below which sperm concentration is expected to influence the time it takes to conceive.”

The Figures Could Be Even Worse for the General Population Although the researchers took into account as many variables that could affect the results that they could find, not all of the possible factors were available. For instance, while they were able to adjust for age, time of year, and the center where the sperm sample was given, plus the fertilization technique, they could not adjust for socio-economic factors such as lifestyle, weight, and smoking, which can affect sperm count and quality. But, in their discussion about this, the authors suggest even though ART is available to all in France, it tends to be people with more years of education who use it, and they are less likely to smoke and be overweight. So they argue: “… 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.”