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Study: Men have biological clocks, too

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New research suggests that men who choose to delay fatherhood may be reducing their chance of successful conception. CNN's Christy Feig reports (February 6)
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(CNN) -- Women aren't the only ones with a ticking biological clock. A new study adds to the evidence that men's fertility declines with age, too.

"If men are choosing to delay fatherhood, they may want to reconsider," said Dr. Brenda Eskenazi, a professor at the University of California at Berkeley and one of the lead researchers of the study. "There may be an impact on the probability that they will be able to father a child."

The findings, appearing in this week's British journal Human Reproduction, appears at a time when men are waiting later than ever to start a family. Since 1980, there has been an almost 25 percent increase in men aged 35 to 54 fathering children in the United States, according to the National Center for Health Statistics.

Eskenazi and her team looked at 97 men, aged 22 to 80, and found that, as men age, the quality of their sperm declines.

"We're finding that there is a smaller volume, which would mean there would be fewer numbers of sperm," she said. "And also that the sperm get slower and less aimed at the goal -- they're not swimming directly to the egg."

This action by the sperm, called progressive motility, started to decrease in men in their 20s. By age 30, the probability of progressive motility being abnormal is about 50 percent, increasing to 82 percent by age 80.

This all means that it could take longer to conceive a baby or it may never happen.

But unlike women, men's biological clock appears to tick more slowly.

"It seems to be about a decade-and-a-half to two decades later than in the female," said Dr. Robert Stillman of the Shady Grove Fertility Clinic in Maryland. "And if we put that in the mid-30s towards 40 in the female, it's going to be the 50s and certainly into the 60s in the men."

The researchers didn't look at reasons for the decline, but previous studies have found that genetic damage in sperm starting as early as age 35, might play a role.

For now, some experts recommend avoiding environmental toxins like smoking and alcohol if men want to increase their chances of being a father.

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