As men get older, the genetic quality of sperm deteriorates thereby increasing a man's risk of being infertile, fathering unsuccessful pregnancies and passing along possible genetic diseases like dwarfism to his offspring.

These were the indications of a new research led by scientists at Lawrence Livermore National Laboratory (LLNL) and the University of California, Berkeley which found a steady increase in sperm DNA fragmentation with increasing age of the study participants, along with increases in a gene mutation that causes achondroplasia, or dwarfism.

"This study shows that men who wait until they're older to have children are not only risking difficulties conceiving, they could also be increasing the risk of having children with genetic problems," said co-lead author Andrew Wyrobek of LLNL.

"We know that women have a biological time clock," said co-lead author Brenda Eskenazi of UC Berkeley's School of Public Health, "with an increase in risk of miscarriage and producing children with trisomy (an extra chromosome, such as in Downs syndrome) as women age, and with a seemingly abrupt end of fertility around perimenopause.

Our research suggests that men, too, have a biological time clock--only it is different. Men seem to have a gradual rather than an abrupt change in fertility and in the potential ability to produce viable healthy offspring."

This only means that in order to have "genetically superior" offsprings, men should think about having a child (or children) not too late in their reproductive years.

This study entitled "Advancing age has differential effects on DNA damage, chromatin integrity, gene mutations, and aneuploidies (chromosome abnormalities) in sperm," appeared first week of June in the online edition of the Proceedings of the National Academy of Sciences.

Read more at Lawrence Livermore National Laboratory.