(RxWiki News) As the world around us continues changing, what's going on inside us can change too. Changes in the environment may play a part in long-term decline in French men's sperm quality.
A recent study found sperm count and sperm quality have steadily decreased in French men over the past 17 years.
During this time, there has been a 32 percent drop in their sperm count. There was also a 33 percent drop in the percentage of normally formed sperm.
"Eat a balanced diet."
The study, led by M. Rolland, of the Environmental Health Department at the Institut de Veille Sanitaire in France, aimed to uncover trends of sperm count and sperm quality in French men over 17 years.
The researchers included 26,609 French men in the study who all had infertile female partners. The men, aged 18 to 70, and their partners were undergoing assisted reproduction at 126 centers across France.
The researchers used samples of the men's semen from the centers and assessed the concentration of sperm in the semen, the number of sperm showing movement and the number of sperm that were complete and normal in each sample over time.
They accounted for the men's age, the time of year and differences in sample collection and storage at the assisted reproduction facilities. The researchers found that both the quality and the number of sperm in men is decreasing over time. The men were losing about 1.9 percent of their sperm each year.
The researchers also saw a decrease over those 17 years in the percentage of sperm that were complete and normal, by about 33 percent.
Across the full time span of the study, the researchers did not see any trends related to the percentage of sperm showing movement, but there was a tiny increase in how many of the sperm moved between 1994 and 1998.
The study was not able to control for men's socioeconomic status, and couples undergoing assisted reproductive technology are likely to have greater income and a higher education than the general population.
This means the study participants may also be less likely to smoke or be overweight, since these are more strongly associated with lower education and income. Smoking and being overweight are also known to negatively affect sperm quality.
In addition, the data on the decrease in the sperm's normal shape might be skewed slightly by changes in how their shape has been measured over the years.
The study was not designed to discover what might be causing the drop in sperm count and quality. The researchers suggested that poor diet and/or exposure to chemicals in the environment that disrupt hormones might play a part.
There also may be environmental influences on genes that are then inherited by the next generation. Any of these possibilities, however, requires more research.
The authors did say that this study presents a "serious public health warning." They suggest public monitoring systems that make it easier to track trends in human reproductive health. The study was published December 5 in the journal Human Reproduction. The research was not externally funded, and the authors declared no conflicts of interest.