Fertility problems in men are as likely to be caused by a range of factors including stress as by excessive mobile phone use, according to scientist from the University of Sheffield.

Responding to research released this week, Dr Allan Pacey BSc PhD, a senior lecturer in andrology, said that a link between mobile phone usage and male infertility was "an indirect measure of fertility, not a direct measure".

The study from the Cleveland Clinic Lerner College of Medicine at Case Western Reserve University in Ohio found that those men utilising a cell phone for more than four hours daily experienced a 30 per cent drop in fertility.

Samples taken from attendees of a fertility clinic revealed that the number, quality and ability to swim of sperm decreased in proportion to an increase in mobile phone usage.

However, Dr Pacey said that men should consider the effect of other aspects of their environment on their sperm count, including their stress and exercise levels.

"It's not just mobile phones, its how long they sit down for, whether they wear tight pants, how much they smoke, exercise, obesity. It's a whole suite of things of which mobile phones are probably a part but not the whole story," he commented.

However, Dr Pacey added that it should be remembered that the sperm count of European men does seem to be in decline and that men that are concerned should be aware of risks to their fertility.

He advised not putting off having a baby until later in life. "If you have a dodgy sperm count and your partner's fertility is not great then you're just making things doubly worse for yourself," Dr Pacey said.

A recent study from Reproductive Biology Associates, based in Atlanta in the US, found that women who leave having babies until their late 30s and 40s may be harming the fertility of future daughters, as female eggs are believed to decline in quality the older the woman becomes.

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