Sperm Density Virtually Unchanged in 50 Years
Shanti tells WebMD that medication can also affect sperm counts. "Blood
pressure medication and steroids, including some dietary supplements used by
athletes, can affect sperm counts. And there's evidence that alcohol and
tobacco use may have adverse effects as well.
"The cause for half of all male infertility is not yet known, so we
should continue to look closely at environmental toxins," says Shanti.
"Additionally, the WHO criteria for sperm concentration has changed in
recent years. So comparisons with previous studies should be adjusted
"The most common abnormality we observed was borderline low motility [or
problems with swimming movement]," says Sokol. "And time delays between
collection and analysis may help explain this finding." Sokol tells WebMD
that follow-up studies of geographic toxins and drug-induced effects are
already under way.
- New research shows that sperm density among American men has not
significantly changed since 1950.
- The finding provides evidence against the theory that environmental toxins
are causing sperm counts to decline, but it cannot be completely ruled out
- Anatomical defects and hormonal deficiencies are the most common known
causes of male infertility, but half of all cases have an unknown cause.