Male fertility is plunging. Nearly one in 10 men may be suffering from low fertility, according to a survey published last month. The Male Fertility Study, compiled by Norwich Union Healthcare from a survey of GPs, suggests that 2.5 million British men are affected by low fertility. Many do not know they may be at risk.
The scale of the problem was first recognised back in 1991 when a Danish study found that sperm counts of Western men had fallen by about half in 50 years. Almost 15 years later, scientists are still trying to explain it. But we do know is that male fertility can be far more changeable than in women.
After all, unlike women " who are born with a finite number of eggs " men are continually producing sperm. Indeed, samples from the same men taken as little as a month apart can vary dramatically. 'We've had patients whose sperm has been fine. But on the day of their IVF treatment, the man has had little or no sperm at all because he's had a bad bout of flu,' says Dr Iwan Lewis-Jones, a consultant andrologist at the Liverpool Women's Hospital and an expert in male infertility. Here are some of the other things that scientists believe may have an adverse effect on male fertility...
If you happen to be partial to convenience or fast food " which is often packed full of 'hidden soy' " you may be heading for a host of fertility problems. Scientists believe chemicals in the soya bean mimic oestrogen.
Dr Sheena Lewis, who conducted the latest research, says chemicals found in soya appear to lower sperm count and affect the ability of sperm to swim. 'The results concern us and there need to be further studies,' she says.
A mounting body of evidence reveals that sitting behind the wheel for prolonged periods is bad news for sperm.
Italian researchers found taxi drivers, truckers and other professional drivers all had reduced fertility levels. Another study by French researchers found that even driving for two hours can raise testicle temperature by around 2C. 'Taken together with the data from other studies, the increase in scrotal temperature we measured in drivers could be one of the strongest pieces of evidence yet to explain why the partners of occupational car drivers take longer to conceive,' says Dr Roger Mieusset, the head of the Italian research group. It is possible to minimise the damage by taking hourly breaks from the wheel for 10 minutes.
You don't have to actually drive a car to put your fertility at risk, according to scientists who discovered that traffic pollution can reduce the quality of sperm. They believe nitrogen oxide and lead in exhaust fumes may be to blame. Dr Michele De Rosa and her colleagues at the University of Naples in Italy examined the sperm of 85 men employed at motorway tollgates who, on average, were exposed to traffic fumes six hours a day. They were found to have poorer sperm quality and less active sperm than men of the same age, living in the same area, who were not exposed to traffic pollution.
But Professor Harry Moore of Sheffield University, who is carrying out the biggest study yet to examine the impact of chemicals in the environment on male fertility, is sceptical. 'We know from other studies that there is no relationship between exposure to traffic fumes and reduced fertility of men living in urban areas compared with men living in rural areas,' he says. 'Therefore, if the study suggests anything " and we must remember that a relatively small number of men took part in it " then it's that men would have to be exposed to very high levels before their fertility was affected.'
Years of using a laptop regularly 'may cause irreversible or partially irreversible changes in male reproductive function', according to one study. It is well known that sperm production …