Background: The global decline of human sperm quality remains a matter of debate. Although many prior studies were flawed (more), numerous studies from the international literature describe a global decrease in sperm concentration among men. A recent study from France looked at 26,000 normal men (ages 18 to 70, with infertile female partners) and identified a significant and continuous decrease in sperm concentration and in normal-shaped sperm between 1989 and 2005.
Details: Specifically, there was a 32% reduction in sperm concentration over time. For example, in a 35 year old male the sperm concentration decreased from 74 million to 50 million per milliliter (ml). The percentage of normal-shaped sperm was also significantly decreased by 33%. The results were the same when looking only at men under 50 years. Comorbidities such as obesity and smoking were not accounted, and abstinence time prior to semen analysis could not be accounted for.
Bottom line: The most recent sperm concentration values in French men are above the 15-20 million/ml threshold that is expected to affect fertility. Sperm concentration less than 55 million/ml, however, could increase the amount of time needed to achieve a pregnancy. These changes in French men’s sperm parameters could be linked to an unknown environmental cause (for example, pesticides or components of plastic). Additional studies will be needed to determine if this decline is occurring in all nations, the causes, and whether the decline will continue.