Study shows sperm decline
Scientists believe stress, lifestyles contributing to 59% drop since 1973
Are men’s sperm counts in a slump — for the past 40 or so years?
A new study finds that men in North America, Australia and Europe produced less than half as many sperm in 2011 compared with 1973. Equally alarming: The quality was worse.
The research raises concerns about fertility as well as male health. Studies show that men with lower sperm counts are more vulnerable to certain cancers, heart disease, diabetes and early death.
“I was really scared when I saw this paper,” said Tina Kold Jensen, an epidemiologist and professor at the University of Southern Denmark, who did not participate in the study.
Jensen said she was involved in research 20 years ago that came to the same conclusion but assumed that sperm counts would have stabilized or bounced back since. “I was actually surprised by the findings. I didn’t think it would go on like that.”
The research, published Tuesday in the journal Human Reproduction Update, compiled data from 185 different studies that included nearly 43,000 men in North America, Europe, Australia and New Zealand.
Shanna Swan, the paper’s senior author and a reproductive endocrinologist and professor at the Icahn School of Medicine at Mount Sinai in New York, said she began researching semen counts and quality more than 20 years ago and not believing them.
“I’ve done my best to make those declines go away,” she said, describing the statistical analyses she conducted to try to undercut that research. When she couldn’t, she became convinced that the decline was real.
Sperm counts fell an average of 1.6% a year for an overall decline of 59.3% since 1973, according to the new study. Sperm concentration, ameasure of quality, also declined dramatically over the same period, particularly among fertile men. The trend did not improve or worsen in more recent decades.
The idea of falling sperm counts has been controversial since it was first suggested 25 years ago. Delores Lamb, director of the Center for Reproductive Medicine at Baylor College of Medicine in Houston, still doesn’t buy it. Many factors might affect why a man’s count could be off one day, including stress and time of year.
While she believes studying semen count is crucial, she says much more research is needed to confirm any trend.
Michael Eisenberg, a urologist and assistant professor at Stanford University, agrees that the data have some flaws but says it’s enough to justify further investigation.
“As a species, we should be concerned if there’s a trend toward declining fertility,” he said. “There’s an urgent need to track this a little more rigorously.”
Sperm counts fell an average of 1.6% a year for an overall decline of 59.3% since 1973