Oct. 17, 2002 -- The biological clock may not tick as loudly for men as women, but a new study shows that the hand of time is also unkind to men when it comes to the quality of their sperm.
For the first time, researchers have found that older men's immune systems do not get rid of defective sperm as effectively as younger men. And they also found a link between increasing age and the number of defective sperm a man has.
Study researcher Narendra P. Singh, MD, of the University of Washington in Seattle, and colleagues presented their findings this week at the 58th Annual Meeting of the American Society for Reproductive Medicine (ASRM).
It's already known that the quality and quantity of women's eggs declines with age, but now researchers say a similar process may be at work in men. Although women are born with all the eggs she will ever have at birth, men's supply of sperm is renewed throughout his life.
This sperm renewal process is complex. For example, older sperm cells are pre-programmed to die off once they become damaged in order to make way for fresh sperm.
But the study, which compared semen samples from 60 men between the ages of 22 and 60, found that this dying off decreases with age, and the defective sperm weren't eliminated as efficiently as they were in younger men.
Researchers also found that men over 35 had more abnormalities in sperm movement and more damaged sperm with more seriously damaged DNA than the younger men.
The study researchers say that continued exposure to environmental hazards may be responsible for the lower sperm quality and consequent fertility problems found in older men.
"Avoiding damaging environmental exposures is important to maintaining optimal fertility for both men and women. While there's nothing anyone can do about getting older, men who want to retain their own best capacity to father a child should try to minimize contact with toxic agents and maintain a healthy lifestyle," says William Keye Jr., MD, president of the ASRM, in a news release.