The reproductive health of the average male is in sharp decline, the world’s largest study of the quality and concentration of sperm has found.
Between 1989 and 2005, average sperm counts fell by a third in the study of 26,000 men, increasing their risk of infertility. The amount of healthy sperm was also reduced, by a similar proportion.
The findings confirm research over the past 20 years that has shown sperm counts declining in many countries across the world. The decline occurred progressively throughout the 17-year period, suggesting that it could be continuing.
The results, reported in the journal Human Reproduction, showed the concentration of sperm per millilitre of semen declined progressively by 1.9% a year throughout the 17 years – from 73.6 million sperm per millilitre in 1989 to 49.9 million/ml in 2005. The proportion of normally formed sperm also decreased by 33.4% over the same period.
The scientists said the results constituted a “serious public health warning” and that the link with the environment “particularly needs to be determined”.
The worldwide fall in sperm counts has been accompanied by a rise in testicular cancer – rates have doubled in the last 30 years – and in other male sexual disorders such as undescended testes, which are indicative of a “worrying pattern”, scientists say.
Richard Sharpe, professor of reproductive health at Edinburgh Uni and an international expert on toxins in the environment, said the study was “hugely impressive” and answered sceptics who doubted whether the global decline was real.
“Something in our modern lifestyle, diet or environment is causing this and it is getting progressively worse. We still do not know which are the most important factors but the most likely are … a high-fat diet and environmental chemical exposures.”
Suggestions include reducing exposure to industrial chemicals such as those used in making plastics – they can mimic the female hormone oestrogen countering male hormones.