Dec. 19, 2003 -- As a man ages, his sperm become damaged -- the result of damaged DNA, a new study shows. This new finding could lead to better sperm selection processes in infertility treatment, researchers say.
It is well known that female fertility declines with age as a result of impaired egg quality. Researchers are finding that men's fertility is similarly affected, writes lead researcher Narendra P. Singh, MBBS, MS, with the University of Washington in Seattle.
Especially once he gets past age 35, it often takes 12 months or more for a man to impregnate his female partner, explains Singh. If he's over age 40, the risk of miscarriage is great -- especially if his partner is over age 35. It's why so many older couples seek expensive infertility treatment.
DNA damage in both developing and mature sperm are likely the cause of many fertility problems, writes Singh. While healthier sperm ideally should fertilize an egg, sperm with damaged DNA can also fertilize -- which may result in problems for the fertilized, developing egg.
In Singh's study, the sperm of 66 men between ages 20 and 57 were analyzed for both DNA damage and apoptosis (programmed cell death).
Researchers found that, as men got older, the percentage of DNA-damaged sperm was higher.
Men between 36 and 57 had the most DNA damage; men between 20 and 35 had much less DNA damage.
At the same time, in the older men, the programmed cell death of damaged sperm became much less efficient -- contributing to the increase of damaged sperm, reports Singh.
DNA damage was found in men of all ages, so it's not the only factor influencing sperm damage, he adds. In fact, some younger men had more DNA damage than older men. Also, some men had a wider range of damaged DNA -- possibly indicating varying sensitivities of individual sperm to damage.
It's all good information for frustrated couples seeking infertility treatment. An improved sperm-selection method might help couples that want a child, adds Singh.
SOURCE: Singh, N. Fertility and Sterility, December 2003; vol 80: pp 1420-1430.