men's sperm count declined in the past several decades?

overhead this on a health conversation.

Posted Answers


A:

Sperm Count Decline Confirmed
Monday November 24 1997 4:58 PM EST

Expert: Sperm Counts Falling Around the World

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - Modern living is hitting men right where it hurts the most, with sperm counts falling more quickly than anyone thought, U.S. researchers said Monday.

Experts who set out to dispel fears of falling sperm counts found they were even lower than had been reported. "I think this study will change the debate about sperm decline from 'if' to 'why'," said Shanna Swan, chief of the reproductive epidemiology section at the California Department of Health Services, who led the study.

The debate has been bubbling since 1992, when Niels Skakkebaek, Elisabeth Carlsen and colleagues at Copenhagen University reported sperm counts were falling around the world, based on an analysis of 61 different studies. Their announcement caused a flurry of debate, and studies published since have shown conflicting results. British research found that men born in the 1970s had 25 percent fewer sperm than those born in the 1950s, while Harry Fisch of New York's Columbia-Presbyterian Medical Center found men there had high sperm counts, with no evidence of a decline.

Swan's group re-analyzed the 61 studies. "Overall, in Europe and the United States there is a strong and significant decline," she told Reuters. There could be regional variations, which would account for the New York findings and similar findings in Seattle and Finland, she added in an interview.

The National Institutes of Health agreed. "Their analysis of data collected from 1938 to 1990 indicates that sperm densities in the United States have exhibited an average annual decrease of 1.5 million sperm per milliliter of collected sample, or about 1.5 percent per year," the NIH said in a statement. "Those in European countries have declined at about twice that rate (3.1 percent per year)."

Sperm counts seemed to be going up slightly in developing countries, but Swan said the data from these areas was sketchy and did not go back as far as the U.S. and European results. Swan, whose findings will be published in the journal of the National Institute of Environmental Health Services, one of the NIH agencies, said she approached the task expecting to disprove the theory. "When I first read Carlsen I was at first, frankly, suspicious because of its simplicity," she said.

But after careful analysis, she changed her mind. What is the cause? "Once we rule out differences such as smoking, temperature, age and ethnicity, what we will have left are environmental factors," Swan said. She, and many other experts, blame persistent organic pollutants (POPs), which range from pesticides such as DDT to industrial chemicals like PCBs. All have been shown to act like hormones such as estrogens, which can either bring out feminine characteristics or work to counteract male hormones.

Swan is part of a National Academy of Sciences committee writing a report on such chemicals. The Academy has not reviewed her sperm research. Swan said fertility was not the big issue, as babies were still being born. "However, sperm count is a marker, a red flag ... for testicular cancer." she said.

In November 1996 the U.S. Congress passed legislation requiring the Environmental Protections Agency (EPA) to develop ways to test substances to see if they disrupt human or animal hormones. In May, the European Environment Agency, European Commission, World Health Organization and other organizations agreed there was an apparent decline in sperm count in some countries, and evidence that rates of testicular cancer were increasing.

Declining sperm count
Semen quality has declined among men born in France since 1950
EDITOR,--Several recent papers have reported a possible decrease in sperm counts.1 2 3 4 5 Three of them were based on data collected in single laboratories, from a relatively low number of fertile men (between 302 and 1351).1 2 3 Their conclusions were in favour of a decline related to the year of birth1 or to the year of the measurement3 or of no change.2 The two other papers were reviews of the same published papers, the first concluding that sperm counts had decreased and the second that they had increased during the past 20 years.4 5 The existence of the French national register on in vitro fertilisation enabled us to analyse this phenomenon by using a large database.6 This register, which contains details of 90% of all cycles of in vitro fertilisation in France on an individual basis, has recorded sperm counts since 1989.

To avoid any bias due to the increasing proportion of in vitro fertilisation that is performed for infertility of male origin, we selected only couples with pure tubal infertility and in which the husband's semen was normal at the examination before in vitro fertilisation was attempted (sperm count >20 million/ml, total motility at 1 hour >40%, and normal morphology >40%). Thus we analysed 19 848 sperm counts (in 7714 men) measured on the day of in vitro fertilisation. Data were analysed with the generalised linear model (SAS Software, SAS Institute, Cary, NC, USA), with both the actual sperm count and the value after logarithmic transformation being analysed.

The most impressive variations were noted for the year of birth (table 1), since the sperm counts were fairly stable for men born before 1950 and decreased regularly for men born from 1950 to 1975. The decrease was observed whatever the year of collection. When the data were analysed by year of collection a decrease was observed only between 1991 and 1992, the figures being stable before and after these dates. The results were similar when analysis was restricted to the first ejaculates. The period of abstinence was not recorded in the register; for in vitro fertilisation, however, couples are requested to observe two to four days' abstinence before the semen collection.


 Answer by email

Share this with your friends