had children from their late 30s to early 50s - had longer telomeres.

"In most cells, telomeres shorten with age. But in sperm, telomeres lengthen with age," lead researcher Dan Eisenberg, from Northwestern University's Department of Anthropology, said.

"Men who reproduce at an older age father children with longer telomeres compared with men who reproduce at a younger age.

"An individual's telomere length increased not only with their father's age at their birth, but also further increased with their paternal grandfather's age at their father's birth.

"This suggests delayed paternal reproduction can lead to cumulative, multi-generational increases in telomere length in descendants, which could promote longevity."

The study said the telomeres lengthened whether the father and children were rich or poor, overweight or fit.

Australian men are becoming fathers later in life, with themedian age of fathers increasing from 31 to 34 between 1990 and 2010, and more men are becoming fathers in their late 50s and early 60s.

In 2010, 777 men aged 55 to 59 fathered a child, up from 674 in 2004 and 516 in 2000. The number of men in their 60s having babies has also increased from 226 in 2000 to 408 in 2010.

Previous studies have linked older fathers with increased chances of having children with health problems, with a recent US study of 132,000 men finding children of those over 45 were nearly six times more likely to have an autism spectrum disorder.

Another US study showed men over 50 had a 15 per cent higher chance of having a baby with birth defects.