Advancing paternal age is an independent predictor of live birth success rates with stimulated intrauterine inseminations, according to data released at the 2014 Annual Meeting of the American Urological Association (AUA).
Dr. Natan Bar-Chama, of Mount Sinai School of Medicine in New York, NY, and colleagues examined the impact of paternal age on stimulated intrauterine inseminations (IUI) cycle success using data from 18,806 stimulated IUI cycles conducted at their institution over a recent 8-year period. Success was defined as live birth.
The study is the largest to date to track outcomes from stimulated IUIs.
After adjusting for standard predictors of live birth including maternal age, maternal body mass index (BMI), follicle-stimulating hormone levels and antral follicle count, a 20% decline per decade of advanced paternal age (P < 0.0001) was observed in stimulated IUI success rates.
The decline appears to start when men are in their 20s.
The impact of paternal age on the decrease in the live birth rate was seen irrespective of the stimulation protocol.
"Historically we have looked at female age as a limiting factor in fertility, and our take-home message is that paternal age is also a contributor," says Dr. Bar-Chama, who is also the director of male reproductive medicine and surgery at Reproductive Medicine Associates of New York.
The mean maternal age in the cohort was 36.4 years, and the mean paternal age was 38.4 years.
'Effect of age on fertility is both maternal and paternal'
"Some earlier studies have shown a decline in semen quality with age as well as the ability of sperm from older men to fertilize eggs and achieve pregnancy with advanced reproductive technologies, such as in vitro fertilization [IVF]," Dr. Bar-Chama says, and adds:
"In addition, advanced paternal age has been found to be associated with a variety of disorders including schizophrenia, autism, and attention-deficit disorder. Our new data convincingly demonstrate that advancing paternal age also leads to a decline in successful stimulated IUIs."
Stimulated IUI is one of the most widely used techniques to assist couples with infertility and is actually more popular than the more "high-tech" approach involving in vitro fertilization, he notes.
Dr. Bar-Chama recommends that when counseling couples, physicians need to emphasize that the effect of age on fertility is both maternal and paternal.
Finally, he called for future research aimed at identifying causes for the age-associated decline in male fertility. "In particular, we need to examine possible risk factors that might play a role in this decline," he says. "In fact, if we can identify modifiable risk factors, we may provide therapies that will be able to counterbalance this observed negative effect of paternal aging on fertility."
Jill Stein is a Paris-based freelance medical writer.