The drop off in fertility for women after the age of 35 is well known. Now Australian researchers have found that men face a similar decline at the same age.

Sydney IVF researchers took sperm samples from more than 3,000 men and their DNA or genetic make-up was examined.

Mark Bowman from Sydney IVF says they found older men had less chance of fathering a child.

"They cannot take fertility absolutely for granted, there is also an impact of male age on fertility," he said.

Dr Kylie de Boer says the samples showed that as men age their sperm starts to fragment or break down, which makes the sperm less viable for fertilising the egg.

The older the man, the more damage, researchers found.

"The rate of DNA fragmentation of sperm increased with age and there was a significant DNA damage to sperm when the man was above the age of 35," Mr Bowman said.

And while the Rupert Murdochs of this world have fathered children later in life, the new research suggests they are the exception, not the rule.

One in six Australian couples end up seeking medical treatment because they cannot conceive and in almost half of those cases it is due to male infertility.

Mr Bowman says a healthy lifestyle is one way of holding back the years.

"The messages would be limit alcohol, don't smoke, eat a healthy diet, take anti-oxidants and probably spend more time with your partner," he said.