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Friday, 17 March, 2000, 11:22 GMT
Modern man still virile
Sperm
Sperm counts are holding steady
Despite grim warnings to the contrary, modern men in the US are just as virile as their forefathers, according to research.

Scientists have suggested that many aspects of modern living - including pollution and tight underwear - have led to reduced sperm counts.

But new research from the University of Southern California's Keck School of Medicine has found that sperm densities are no different now than they were in major studies done in the 1950s.


Everything in our study indicates that the average man's sperm count is not changing

Dr Rebecca Sokol, University of Southern California
Researcher Dr Rebecca Sokol said: "Everything in our study indicates that the average man's sperm count is not changing."

The research is published in the journal Fertility and Sterility.

The researchers examined semen samples collected from 1,385 men, whose wives were seeking infertility treatment, at the Los Angeles County Medical Centre from 1994 to 1997.

It was found that about half (52%) of the samples showed some abnormality - mostly slow sperm.

One in five (18%) samples had below-normal sperm concentration and 14% had abnormally shaped sperm.

The results of average sperm counts were identical to those reported in classic studies from 1950s, the researchers said.

Previous studies, looking to substantiate claims that men's sperm counts in the Western world have been dropping since the 1950s, have cited environmental pollution, sedentary lifestyles, tight underwear and iodised salt, as possible causes.

Dr Sokol noted that the pool of men who provided semen samples for the Keck study primarily worked in blue-collar jobs that would have exposed them to significant environmental toxins.

Therefore, if pollutants caused a drop in sperm count, that would have shown up in the study findings.

Much speculation

Spem samples
Samples must contain sperm that can swim effectively
A controversial paper published in The Lancet medical journal in the early 1990s suggested sperm counts had fallen by 50%.

However, Dr Gulam Bahadur, of the fertility unit at The Middlesex Hospital, London, failed to replicate The Lancet findings.

His team found that sperm counts had fallen during the 1970s - but only in some geographical areas.

He said there were also indications that sperm counts had stabilised since then.

Dr Bahadur said: "All the reasons put forward so far for why sperm counts may have fallen are entirely speculative.

"But it is possible that it may be linked to oestrogen-mimicking compounds as pollutants in the water supply or diet, or perhaps due to things in the air that we breathe."

Sperm count is an important factor in fertility, but not the only one - sperm must be able to swim properly if they are ever to fertilise an egg.

Dr Bahadur said his lab had found that samples containing less than 4million motile sperm per millilitre of semen were half as likely to successfully fertilise an egg.

The average man is thought to produce about 20million sperm per millilitre of semen.

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See also:

02 Mar 00 | Health
Sperm count fall blamed on salt
05 Oct 99 | Health
UK may import sperm
13 May 99 | Health
Sperm analysis 'varies wildly'
13 Sep 99 | Health
Ignorance over male infertility
28 Feb 00 | Health
Sperm boost may aid fertility
02 Jan 00 | Health
Hope for infertile men
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