Stuck counting sheep while your hubby sleeps soundly? A new study suggests you're not alone. McGill University researchers explain that while men and women tend to go to bed and rise at roughly the same times, women have more trouble staying asleep—because their internal body clocks are dfferent, reports HealthDay News.

"Women’s body clock causes them to fall asleep and wake up earlier than men," says study author Diane Boivin of McGill University in a release.

More From Newser

"The reason is simple: their body clock is shifted to a more easterly time zone.” Researchers came to that conclusion after measuring levels of sleep and alertness in 15 men and 11 women monitored over 36 hours. Female participants appeared more tired and therefore less alert at night than men, meaning they may be "less biologically suited for night work" and more likely to suffer work-related injuries, writes Boivin. The female sleep signal was also weaker than the male signal at the end of a night, meaning women may have "a difficult time staying asleep later in the night," says a UCLA professor. "Perhaps women are predisposed to having insomnia based on their circadian phase." The study could also help explain why women tend to be more likely to feel drowsy during the day and more likely to suffer from sleep problems, researchers say.

This article originally appeared on Newser: Women's Internal Clocks May Explain Sleep Trouble