Sperm Density Virtually Unchanged in 50 Years
March 17, 2000 (Atlanta) -- Sperm density has not changed significantly
since 1950, according to a report in the March issue of Fertility and
Sterility. Researchers say the findings refute the notion that exposure to
environmental toxins has caused sperm quality to decline.
Because there's been considerable concern that sperm quality is declining in
the U.S. and other industrialized countries, researchers collected semen
specimens from 1,400 men over 36 months. The men were partners of women who
were being evaluated for problems with fertility, but it was not known whether
any of the infertility was due to problems with sperm. Semen, the fluid that
carries the sperm, was analyzed using criteria accepted by the World Health
Approximately half the samples had at least one sperm abnormality. Flaws
included problems with the sperm's swimming movement, their shape, or not
having any sperm at all. The lead author says the findings are consistent with
"Our findings are very similar to a landmark study conducted in
1950," says Rebecca Sokol, MD, a professor of medicine, obstetrics and
gynecology at the University of Southern California School of Medicine.
"And similarity over time refutes the hypothesis that sperm quality is
declining in the United States."
Previous reports about sperm quality have presented conflicting results.
Some researchers have concluded that today's men are just as fertile as their
grandfathers were. Others proposed that the opposite seemed to be true, while
still other scientists have reported a dead heat between the generations.
Observers note the discrepancy shows that larger studies are needed, using
standardized methods to count the squirming little subjects.
"It's very difficult to compare sperm counts from one laboratory to the
other," says Harry Fisch, MD, a urology professor at Columbia-Presbyterian
Medical Center in New York. "That's why the emphasis now and in the future
will be to standardize how we do semen analysis so we can have a long-ranging
understanding of what's going on."
Sokol tells WebMD that her findings show there may be regional differences
in sperm quality. Her results were similar to what others found with Chinese
men, but differ significantly from a French study. "This suggests that
there may indeed be geographic differences in sperm concentrations," says
Sokol. "But overall, research shows that sperm density has changed very
little in the last 50 years."
Physicians say anatomical defects and hormonal deficiencies are common
causes of male infertility.
"Anatomical defects are caused by birth anomalies [defects], surgery,
trauma, and infection," says Aida Shanti, MD, medical director of in vitro
fertilization at the Emory Clinic and assistant professor of obstetrics and
gynecology at Emory University School of Medicine in Atlanta. "And hormonal
deficiencies refer to a lack of testosterone or its chemical