Global Sperm Count Shows Steady Decline

Researchers at the Institut de Veille Sanitaire (Saint Maurice, France) used semen analysis data from 26,609 men attending 126 centers registered in the French assisted reproduction technology (ART) database Fivnat. Although the semen data came from ART centers, the men themselves were not having treatment, but their female partners, mostly for blocked or missing Fallopian tubes. The temporal trends of semen quality were modeled using a generalized additive model that allowed for nonlinear relationships between variables, and were adjusted for season and age.

The researchers found that over the 17 years up to and including 2005, there was 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 average sperm count fell from 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 researchers also found there was a slight increase in sperm motility, with the proportion of motile sperm rising from 49.5% in 1989 to 53.6% in 2005. The study was published early online on December 4, 2012, in Human Reproduction.

“This is the most important study carried out in France and probably in the world considering that you have a sample that's close to the general population,” said study coauthor Joëlle Le Moal, PhD. “Although 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.”

The results are consistent with a 20-year-old British Medical Journal review that found sperm counts dropped by half between 1938 and 1990 in developed countries. A global decrease in human sperm quality is still debated as geographical differences have been shown, and many criticisms have risen concerning studies with small and biased study populations or inappropriate statistical methodology. However, growing biological, toxicological, experimental, and human exposure data support a hypothesis that fetal exposure to endocrine disruptors could impair reproductive outcomes.

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