Testosterone Drops in Dads Sharing Beds With Kids

By Rita Rubin WebMD Health News

Sept. 5, 2012 -- Dads who sleep in the same bed as their children may see a drop in their testosterone levels, a study shows.

"This is the first study that's ever been done on this," says researcher Lee Gettler, PhD, an assistant research professor at Notre Dame. "No one before had ever asked the question as to whether co-sleeping affects men's physiology."

The study is published in the journal PLoS One. It follows an earlier study that shows men's testosterone levels drop when they become fathers.

Evidence from studies in animals suggests that high testosterone levels, which help males attract a mate, might interfere with fathers' investment in their children.

Research also shows that men with higher testosterone levels aren't as responsive to a crying infant, while those with lower levels tend to be more hands-on dads.

The study was conducted with 362 young Filipino men. About 92% of those men said they slept next to their children.

Gettler first assessed the Filipino men's testosterone levels in 2005, before they became fathers. He checked testosterone levels again in 2009, when the men had at least one child.

Men with lower testosterone in 2005 were no more likely to sleep with their children after becoming dads than men with elevated testosterone. In 2009, though, the bed-sharing fathers had lower testosterone than the other men in the evening but not in the morning.

"I was surprised that there was no difference in the morning," Gettler says. After all, he says, research has shown that a lack of sleep, which might be expected in men who sleep with their young children, can lower testosterone levels. His study did not collect information about sleep quality or duration.

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Testosterone Drops in Dads Sharing Beds With Kids

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