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    Sperm Density Virtually Unchanged in 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 precursors."

    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 accordingly."

    "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.

    Vital Information:

    • 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 yet.
    • Anatomical defects and hormonal deficiencies are the most common known causes of male infertility, but half of all cases have an unknown cause.
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