By Jim Hotaling, M.D.
Gawker recently reported on an article in the scientific journal Human Reproduction that found sperm numbers and shape to worsen in France during a 16 year period. Studies that claim sperm are declining worldwide have been published for at least the last 20 years. If the trend is true, one guess for its cause was suggested by the Danish scientist Niels Skakkebaek, who argues that chemicals in materials such as plastics act as synthetic hormones that interrupt a man’s own internal natural hormones.
The Human Reproduction article is well designed, studying a very large group of 26,609 men from infertility clinics in France from 1989 to 2005. Each man had two semen analyses, which adds to the strength of the paper as sperm counts change much even from day to day. The scientists concluded that sperm count decreased 1.9% per year in France during the time period of the study.
Before jumping to the conclusion that the fertility of French men is dipping, there are some important limitations of the study. To their credit, the scientists state most of them clearly in their paper. The first is that the scientists studied men showing up in fertility clinics. These men as a group are probably different that the average guy in France. Second, the men got older during the study. While the age increase was small, 34.2 to 35.9 years, and may not mean much, the deCODE study suggests that changes in sperm may start early in a man’s life. Third, giving a sample in an fertility lab may not be the same as when it’s delivered naturally.
This study probably isn’t great cause for concern that sperm are on a steep decline in France. Even if the numbers are going down a bit, there’s still plenty of sperm in these men to do the job.