October 17, 2011
Colorado Researchers Confirm Men, like Women, have a Ticking Biological Clock that Impacts Fertility
DENVER, Colo. – October 17, 2011 – A new study conducted by the Colorado Center for Reproductive Medicine (CCRM) in conjunction with the National Foundation for Fertility Research (NFFR) concludes that sperm from middle-aged and older male mice is less likely to lead to a successful pregnancy. The study, the first-of-its-kind, found that sperm quality began to decrease in males at mid-life, 12 months and older (equivalent to forty and older for human males).
“This is not a study observing male factor infertility. Rather, this is a study about once fertile males becoming infertile because of age,” said Mandy Katz-Jaffe, PhD, Scientific Director of NFFR. “We were able to document when sperm from older males begins to suffer quality problems, and to understand the impact of older sperm on reproductive outcome.”
This is the first longitudinal study following males over a lifetime to directly correlate sperm aging with reproductive success. Ten young male mice with proven fertility were mated every month during their lifetimes as they naturally aged with fertile young females. “This study is unique because we were able to remove infertility related to the female aging from the equation and focus solely on the male,” said Katz-Jaffe. “This is something that is impossible to accomplish with human studies.”
This study found that when proven fertile male mice reached mid-life (12 months = forties):
- Eggs were less likely to be fertilized by aged sperm.
- Embryos were less likely to develop in vitro.
- Embryos were less likely to implant in the uterus.
- Natural conceptions were far fewer. Only 50 percent achieved pregnancy naturally at 12 months (forties) and 10 percent naturally at 15 months (fifties).
- Assisted reproductive technologies (ART) improved the chance of clinical pregnancy.
- The few successful natural conceptions with aged sperm resulted in significantly smaller fetuses and placental weight.
“There is much focus in society on the ‘maternal biological clock.’ This study shows us that we also need to be concerned about the ‘paternal clock,’” said William Schoolcraft, M.D., Founder and Medical Director of CCRM. “Men in their thirties should consider freezing sperm if they plan to wait to have children. Men in their forties and fifties should consult a reproductive endocrinologist if their partner is unable to conceive after six months of active trying.”