Male Biological Clock is Ticking, Too

June 26, 2003 - It takes two to tango, and when it comes to making a baby, the age of both dancers may play an equally important role. A new study shows that the age of the male partner can have just as big an impact on fertility and the time it takes to successfully conceive a child as the age of the mother.

Researchers found it takes up to five times as long for a man over 45 to get a woman pregnant than if he was under 25. Although the impact of age on a woman's fertility has been well-studied, experts say this is the first time such a strong association has been found between age and male fertility in the time it takes to conceive a child.

"It's always been said that men make sperm every day, and women are born with all eggs they're going to have, so the effect of male age on fertility hasn't been perceived as a major issue until now," says researcher Stephen Killick, MD, professor of reproductive medicine at the University of Hull, U.K. "But in this particular case, there was just as strong an association with male age and infertility, and, statistically, it was even stronger than the woman's age."

Fertility Declines With Male Age

The study, published in the June issue of Fertility and Sterility, compared the time to conception among a group of 2,112 pregnant women. Each of the women filled out a questionnaire about the time it took to achieve pregnancy, the age of both partners, and individual lifestyle characteristics of both partners.

Overall, researchers found that age was the most significant factor that affected the time it took to conceive, but there were small relationships with other factors already known to increase the risk of female and male infertility, such as caffeine or alcohol use and smoking.

Killick says the average time to conception for a woman with a male partner under 20 was 4.5 months but that time rose to 26 months for a 50-year-old man. Compared to men who were under 25, men over 45 were nearly five times as likely to have a time to pregnancy of more than one year and more than 12 times as like to have a time to pregnancy of more than two years.

The study also showed that male age remained a strong contributing factor to infertility even after accounting for other factors such as frequency of intercourse and the age of the female partner.

Sexual Function Isn't Everything

Peter Schlegel, MD, acting chairman of the department of urology at Weill Cornell Medical Center in New York City, says there have been a lot of bits and pieces of information on male age and fertility, but "this is the most definitive study to look at the issue and sort out the effects."