As Men Age, Sperm Quality Declines

Washington -- A new research has found that as men age, the quality of their sperm deteriorates, making it more likely they will have trouble becoming fathers and increasing the possibility of having a child with dwarfism.

The study was led by Andrew Wyrobek of Lawrence Livermore National Laboratory and Brenda Eskenazi of the University of California, Berkeley, School of Public Health.

Women's biological time clock has long been known, with older women having an increased risk of miscarriage and of producing children with genetic defects such as Down Syndrome.

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

They disqualified current cigarette smokers and men with current fertility or reproductive problems or who had undergone chemotherapy or radiation treatment for cancer.

The 97 men that took part in the study were healthy, non- smoking, lab employees or retirees ranging in age from 22 to 80 years old.

Men usually started to have an abnormal DNA fragmentation index at the age of 56, the researchers found.

Unlike older women, the changes in sperm did not increase the chance of producing a child with Down Syndrome, they found. But some older fathers did have an increased risk of having children with dwarfism and "a small fraction of men are at increased risks for transmitting multiple genetic and chromosomal defects."
The current study, which will be featured this week in an online edition of proceedings of the National Academy of Sciences, focused on genetic damage or mutations in semen from men of varying ages.

The study was primarily funded by several grants from the National Institute of Environmental Health Sciences, part of the National Institutes of Health, and the U.S. Environmental Protection Agency.