Sperm counts in Japanese men are decreasing and chemicals that disrupt human hormones may be to blame, a medical school professor says.
An analysis of semen samples from 6,000 Japanese men found a 12 percent decrease in the number of sperm over the past three decades, according to an interim report by Yasunori Yoshimura, a professor of obstetrics and gynecology at Keio University.
Samples taken from medical students in the 1970s contained an average of about 65 million sperm per milliliter of semen.
The figures decreased to about 63 million in the 1980s and further dropped to about 57 million in the 1990s, Yoshimura said. But there was no significant change in the ratio of sperm with a normal rate of activity, Yoshimura said. The rate ranged from 75 percent to 78 percent.
According to the World Health Organization criteria, normal semen should contain a minimum of 20 million sperm per milliliter and the activity ratio should be 50 percent or more.
Yoshimura's survey is the first of its kind in the country to be conducted in large scale and the professor is scheduled to report the results to an academic society meeting starting on Thursday in Osaka. Environmental chemicals that mimic human hormones could have a role in the decline in sperm counts, Yoshimura said.
Other factors like changes in Japanese dietary habits and lifestyle could also play a role, he said. Scientists need to analyze the semen samples for amounts of environmental hormones, he said.
Determining the amounts of the chemicals suspected of affecting humans, which include dioxin, is necessary to prove the link, he said.
Keio University has semen samples from 25,000 donors, many from Keio medical school students aged 18 to 25. The samples are used for artificial insemination in cases where the man has infertility problems.
Keio University hospital was the first in the country to use artificial insemination, in 1949. Since then, about 11,000 babies have been born in the hospital using the technique. Yoshimura said he has access to the additional samples and is continuing his study.
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