Female rodents appear to be more resilient to sleep deprivation as a result of their hormones, according to two studies being presented at Neuroscience 2023, the annual meeting of the Society for Neuroscience, being held in Washington D.C. from November 11-15.

One of these studies finds that hormonal changes in female mice make them more resilient than males to lack of sleep, while the other study reveals that the effect of estrogen hormones on sleep in rats is moderated by a specific set of cells in the brain called astrocytes.

sleep deprivation

Female sex hormones have been long thought to play a role in sleep and sleep deprivation, as women are twice as likely as men to experience sleep disruptions, especially around puberty, menarche and menopause.

“It is estimated that 35 percent to 50 percent of perimenopausal/menopausal women will report sleep problems, as compared to approximately 15 percent of the general population,” Jessica Mong, co-author of one of the studies and professor of neuropharmacology at the University of Maryland School of Medicine.

Mong and her colleagues found that astrocyte cells, which are non-neuronal cells in the preoptic area of the brain—an area involved in sleep regulation—may mediate how estrogen hormones affect sleep.

“Astrocytes are a type of glial cells (glial comes from the Latin meaning “glue”). It was thought that these glial cells, like the astrocyte were just holding the brain and the neurons together. In the past three decades, research has shown this is not the case. But a role for astrocytes in mediating sleep is a relativity recent finding. Moreover, a role in estrogen action over sleep is completely novel,” Mong said.

The researchers inhibited astrocytes in rats, and found that it prevented the action of estrogen on sleep.

“This suggests that [estrogen] may be stimulating or activating the astrocytes which then signal to the sleep-controlling neurons in the [preoptic area],” Mong said.

“This is a significant finding as it is one of the first demonstrations of how [estrogen] may regulate sleep, [and it] may provide future targets for drugs and sleep-aids that are more effective in women. Understanding the role of estrogenic action in the sleep circuity is a critical first step toward a better understanding of the role of estrogens in sleep pathologies and identification of targets for improved interventions for treating sleep disturbances in menopausal women.”

While this study was in rats, Mong thinks that humans may be very similar in how estrogen affects sleep and sleep deprivation.

“This work is translatable to humans as the sleep-wake circuity and pharmacology across mammals is HIGHLY conserved (as one might expect given the overall importance of sleep to health and survival),” Mong said. “Why estrogen affects sleep in humans is also probably an evolutionarily conserved trait related to reproduction. Mammals tend to be more active during times of reproduction. However, although not part of this study, one advantage we have found is that estrogen tends to consolidate vigilance states. For women—especially menopausal women—this may mean less interrupted and better quality sleep.”

The second study found that female mice were more resilient to sleep deprivation than male mice. The researchers discovered that gene expression in female mice after being deprived of sleep was much less changed in female mice than in males: 99 genes had changes in expression in the females, with over 1,100 genes were impacted in males.

“Following one week of individual housing and pre-handling for three days, mice were sleep deprived using gentle handling (tapping and cage shakes as needed) for five hours and then brain regions were dissected and frozen. Non-sleep deprived mice were dissected at the same time to avoid any confounds in gene expression due to variations in circadian time,” the authors wrote in the paper.

“Using an unbiased RNA sequencing approach, we found that females appeared more resilient to changes in gene expression in the hippocampus after acute sleep than similarly aged male mice. Compared to the more than 1,100 significant changes in hippocampal gene expression seen in male mice following acute sleep deprivation, we found only 99 genes in the hippocampus exhibited significant differential expression from sleep deprived females compared to non-sleep deprived females. Moreover, in the proestrus stage, female mice had no significant differential gene expression in the hippocampus between sleep deprived and non-sleep deprived animals.”

“Why we sleep remains one of the major enigmas of neuroscience,” Robert Greene, professor of psychiatry and neuroscience at University of Texas Southwestern Medical Center and moderator of a November 14 press conference where the studies will be presented at Neuroscience, said in a statement.

“Recent neuroscience research is beginning to uncover some of these secrets, including understanding the price of sleep loss on brain function. Further studies show the surprisingly gender-specific gateway to sleep in females and female resilience to sleep loss when sleep is curtailed. Finally, pioneering research on dream sleep may take a step forward with cephalopods, like cuttlefish, that wear their dreams on their skin, potentially providing a unique window into their dream content.”

Source: Newsweek