The reason women tend to wake up earlier and be more prone to insomnia than men may be rooted in biology. Research conducted by the Sleep Medicine department of Brigham and Women’s Hospital in Boston has revealed that the body’s internal clock, called circadian rhythm, ticks faster for women than it does for men. Published in the Proceedings of the National Academies of Science in March, the sleep study found that, without external time cues, women’s brains cycled through a typical “day” six minutes more quickly than men.
Research subjects – 52 women and 105 men ranging in age from 17 to 74 — were placed in an environment devoid of normal day/night time cues, forcing them to rely on the natural circadian rhythm of their brain to determine when it was time to wake up and go to sleep. In both sexes, the natural circadian cycle was slightly longer than 24 hours, ranging from 23-1/2 to 24-1/2 hours in length. However, the circadian cycle exhibited by women was consistently shorter than that of men by an average of 6 minutes. Women also proved to be 2-1/2 times more likely than men to have a circadian cycle that was shorter than the standard 24 hours.