Why do women sleep worse than men?

“The quality of sleep is much more important than its quantity. We conducted a study of 4,000 people and found that interrupted sleep is much more problematic than the number of hours a person sleeps. The main thing is to sleep soundly. “I sleep 4 to 5 hours, but very deeply,” Valentin Fuster, CEO of I Mount Sinai Fuster Heart Hospital, reflected in an interview.

Quality sleep is essential for physical, mental and emotional well-being. For this reason, the biomedical sciences are making “considerable efforts to study the relationships between sex and the mechanisms underlying various disease states and behaviors, including sleep,” explain researchers from the University of Colorado Boulds, who have just published a new animal study. study. This shows that women sleep less, wake up more often and sleep less restfully than men.

The findings, published in the journal Scientific Reports, shed light on what may underlie sleep differences between men and women. They also indicate that they could have broad implications for biomedical research, which for decades has focused primarily on men.

“In humans, men and women have different sleep patterns, which are often explained by lifestyle and caregiving factors,” said lead author Rachel Rowe, assistant professor of integrative physiology. “Our results suggest that biological factors may play a larger role in these sleep differences than previously thought.”

Over the past 20 years, the importance of sleep to public health has become increasingly recognized and research has increased dramatically. Thousands of animal studies have examined how lack of sleep affects the risk of diseases such as diabetes, obesity, Alzheimer’s disease and immune disorders, and how these diseases affect sleep. Mice were often the first to test whether sleeping pills worked and what their side effects were.

No female representation

The study suggests that many of the findings may have been skewed by a lack of female representation. “We found that in the strain of mice most commonly used in biomedical research, sleep behavior varies by sex, and that failing to account for these sex differences can easily lead to misinterpretation of the data,” said Grant Mannino, Ph.D., in psychology. and neurology.

For this non-invasive study, the authors used specialized cages equipped with ultra-sensitive motion sensors to assess the sleep patterns of 267 mice. Males slept a total of about 670 minutes per day, about an hour more than females. This extra sleep was non-rapid eye movement (non-REM) sleep, restorative sleep during which the body works to repair itself.

The study found that women had even shorter periods of sleep; his sleep is more fragmented. “The hypothesis that sex differences in the distribution of sleep-wake behavior may be adaptive is supported by observations in Drosophila, a model commonly used to study the molecular and circuit basis of sleep regulation, where almost all lines of female flies (9000 lines with tested mutations) sleep less than men,” the authors explain. They add that after mating, female flies sleep less than males, likely to meet nutritional needs. Among mammals, female black-eared marmosets with young sleep significantly less than females without young.

“From a biological perspective, it may be that females are designed to be more sensitive to their environment and to be agitated when appropriate because they are typically the ones caring for the young,” Rowe said. “If we slept as deeply as men sleep, we wouldn’t have evolved as a species, would we?”

Cortisol

Stress hormones such as cortisol (which promotes wakefulness) and sex hormones likely play a key role here. For example, women tend to report worse sleep during the period of their menstrual cycle when estrogen and progesterone levels are at their lowest.

Some suggest that women naturally need less sleep. “For me, the question is: Are we putting ourselves under too much stress because we are not getting as much sleep as our husband or male partner and we think our sleep is poor when in fact it is our normal sleep profile? » – said Rowe. n