French men’s sperm quality is dwindling.

A study of 26,609 men whose semen samples were tracked over 17 years, published recently in the journal Human Reproduction, found declines in both sperm concentration and in the number of normally formed sperm. Concentration alone dipped by about a third during the study period.  

The study sample is probably one of the largest in the world on the topic and raises concern that modern lifestyles may harm fertility and health, the researchers wrote. Possible causes include environmental factors such as endocrine disruptors -- chemicals found in plastics or food that interfere with the body’s hormones -- or changes in body mass index and levels of stress, they said.  

“These results indicate a severe and generalized decrease in semen quality in France, possibly since the 1970s, which constitutes a serious public health warning,” wrote the authors, led by Joelle Le Moal of the Institute for Public Health Surveillance in Saint Maurice, France. “This issue could be a growing cause of concern for the next generation’s health.”  

The men studied were partners of women who were infertile and sought assisted reproductive procedures. Their sperm concentration fell about 1.9 percent a year, or 32 percent over the 17 years. The percentage of normally formed sperm declined 33 percent in the study period, which ran from 1989 to 2005. The concentration values reached at the end of the study were low enough to affect the time it takes to conceive, according to the authors.  

Le Moal and her colleagues plan to delve back into the data to see whether men born at certain times were more affected than others and whether they can find geographic patterns. They will also be working with data collected after 2005 to see if the decline continued in subsequent year. Beyond the fertility concern, the state of male sperm can be viewed as a gauge of public health, Le Moal said. 

The drop in sperm count coincides with a rise in cancers in France. Is there also a coincidence that France has 20 nuclear power plants spread around the country?