Scientists say one gender sleeps less and wakes more often than the other

Females sleep less, wake up more often and get less restorative sleep than males, according to a new study. The findings, published in the journal Scientific Reports, shed new light on what causes sleep differences in men and women and could have broad implications for biomedical research, which for decades has focused on males.

“In humans, men and women exhibit distinct sleep patterns, often attributed to lifestyle factors and caregiving roles,” said senior author Rachel Rowe, assistant professor of integrative physiology at University of Colorado Boulder “Our results suggest that biological factors may play a more substantial role in driving these sleep differences than previously recognised.”

Sleep research has exploded in recent years, with thousands of animal studies exploring how insufficient sleep impacts risk of diseases like diabetes, obesity, Alzheimer’s and immune disorders—and how such diseases impact sleep. Meanwhile, mice have often been the first to be tested to see whether new drugs, including medications for sleep, work and what the side effects are.

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But many of those results may have been skewed due to a lack of female representation, the study suggests. “Essentially, we found that the most commonly used mouse strain in biomedical research has sex-specific sleep behaviour and that a failure to properly account for these sex differences can easily lead to flawed interpretations of data,” said first author Grant Mannino, who graduated with degrees in psychology and neuroscience.

For the non-invasive study, the authors used cages lined with ultrasensitive movement sensors to assess the sleep patterns of 267 mice.

Males slept about 670 minutes total per 24-hour period, about an hour more than female mice. That extra sleep was non-Rapid Eye Movement (NREM) sleep—the restorative sleep when the body works to repair itself.

Mice are nocturnal and are “polyphasic sleepers”—napping for a few minutes before arousing briefly to survey their environment and then resuming their slumber. Females, the study found, have even shorter bouts of sleep..

Similar sex differences have been seen in other animals, including fruit flies, rats, zebrafish and birds. Evolutionarily, it makes sense.

“From a biological standpoint, it could be that females are designed to be more sensitive to their environment and be aroused when they need to be because they are typically the one who is caring for the young,” Rowe said. “If we slept as hard as males sleep, we would not move forward as a species, right?”