Heterosexual couples who are trying to conceive should pay more attention to their sleep, new research suggests ― particularly how much sleep the man gets.
Researchers found that men who get either too little or too much sleep decreased their chances of getting pregnant with their partner over a 12-month period by as much as 42 percent, according to data recently presented at the annual conference of the American Society for Reproductive Medicine.
Men who got eight hours of sleep per night had the highest rates of pregnancy with their partners, study author Lauren Wise, a professor in the Department of Epidemiology at Boston University’s School of Public Health, told The Huffington Post.
“Our results suggest that perhaps male fertility could be added to the list of positive health outcomes associated with getting a good night’s sleep,” she said.
The study was the first to record men’s sleep duration and then prospectively measure how that affected those men’s ability to get a partner pregnant, Wise said.
Men who slept more conceived quicker
Wise and her colleagues recruited 790 couples who were planning to get pregnant from all 50 states in the U.S. and all 10 provinces in Canada. The couples answered a series of questions about their sleep patterns and lifestyle in an online survey.
The researchers followed up with the couples for a year to see how quickly they conceived. Men who reported sleeping fewer than six hours a night or nine or more hours a night were 42 percent less likely to get their partner pregnant in any given month compared with men who slept eight hours a night.
It’s possible that an underlying health problem or medical condition negatively affects both sleep and fertility, Wise said.
“We cannot rule out the possibility that other unmeasured factors explain our results, but we controlled for a wide range of variables measured in both the female and male partner,” she explained.
The researchers asked individuals about infertility, the women’s sleep habits, smoking history, alcohol use, stress, physical activity, whether or not the man had previously fathered a child and how often the couples had sex, among other factors. They found that even after controlling for all of those variables, the relationship between a man’s sleep habits and his chances of conceiving with his partner remained.
Men need sleep to produce testosterone
Wise and her colleagues suspect the reason why men’s sleep likely plays such an important role in fertility has to do with testosterone levels. Even though this study did not measure men’s testosterone levels, the hormone is known to play critical roles in the reproductive process. It’s also well documented that the majority of the testosterone men produce happens during sleep, Wise explained.
“Sleep duration and quality are associated with testosterone levels, as well as semen quality,” Wise said.
Still, it’s important to note that the research still doesn’t necessarily show that one behavior (the man not getting enough sleep) was the sole cause of another outcome (having lower chances of getting their female partner pregnant), or that testosterone has anything to do with the results of this study.
Another possibility is that a misaligned circadian rhythm ― when the body’s internal clock is off-kilter ― could be to blame for the reduced fertility among the men, Wise said. Other recent research found that a disturbed circadian rhythm lowers semen quality and had no impact on testosterone levels.
Additional studies that measure testosterone levels in individuals who sleep poorly and also measure how those factors affect the individuals’ fertility would be needed in order to prove that is in fact the reason men who sleep poorly have lower chances of getting a partner pregnant.
For now, the bottom line: If you’re trying to get pregnant, getting good sleep ― especially for the man ― could affect your chances of conceiving in a big way. And it’s not bad for a number of other aspects of your health, too.
Sarah DiGiulio is The Huffington Post’s sleep reporter. You can contact her at firstname.lastname@example.org.