A new study has highlighted significant differences in sleep patterns between males and females, indicating that biological factors have a greater impact than lifestyle in determining sleep styles.
According to SciTechDaily, this finding prompts a reevaluation of previous biomedical research, which often excluded females, leading to potential misunderstandings in the development of sleep-related medications and treatments.
Gender Differences in Sleep Patterns
A recent study conducted by researchers at the University of Colorado Boulder (USA) found that females tend to sleep less, wake up more frequently, and experience less restorative sleep compared to males.
The study, published in Scientific Reports, underscores the biological factors that may explain these differences and highlights the potential impact on biomedical research, which has primarily focused on males.
“In humans, males and females exhibit distinctly different sleep patterns, often attributed to lifestyle factors and caregiving roles,” explained Rachel Rowe, the lead author and associate professor of integrative physiology.
Females tend to sleep less, wake up more often, and experience less restorative sleep compared to males – (Image: Reuters).
“Our study’s results suggest that biological factors may play a much larger role in leading to these sleep differences than previously recognized,” she added.
Sleep research has surged in recent years, with thousands of animal studies exploring how sleep deprivation affects the risk of diseases such as diabetes, obesity, Alzheimer’s, and immune disorders – and conversely, how these diseases affect sleep.
Meanwhile, mice are often the first subjects tested to see how new medications, including sleep drugs, perform and their side effects. However, research indicates that many results may be skewed due to a lack of female representation.
“Essentially, we found that the most commonly used mouse strains in biomedical research exhibit sex-specific sleep behaviors, and failing to account for this difference can easily lead to misinterpretations of data,” said Grant Mannino, a co-author of the study.
The Importance and Impact of Sleep Research
In this non-invasive study, the authors utilized specialized cages with highly sensitive motion sensors to assess the sleep patterns of 267 mice bearing the code “C57BL/6J.” Male mice slept a total of about 670 minutes every 24 hours, which is roughly an hour more than female mice.
This additional sleep portion is attributed to non-rapid eye movement (NREM) sleep – the type of restorative sleep during which the body heals itself.
Mice are nocturnal animals and have a “polyphasic” sleep pattern – sleeping for a few minutes, then waking to observe their surroundings before sleeping again. The study found that female mice exhibited more fragmented sleep.
Similar gender differences were also observed in other species, including fruit flies, rats, zebrafish, and birds. This has evolutionary significance.
“Biologically, females may be designed to be more sensitive to their environment and wake when necessary because they are often the caregivers of young,” Rowe explained. “If women also slept as deeply as men, we might not have evolved as a species.“
Stress hormones like cortisol contribute to alertness, and sex hormones may also play a role. For instance, women often report poorer sleep during their menstrual cycle when estrogen and progesterone levels are at their lowest.
Gender Bias Persists in Research
In 2016, the National Institutes of Health in the United States began requiring scientists applying for animal research funding to consider “sex as a biological variable.” However, research shows that gender bias still exists, which can lead to real consequences.
“We hope our research will encourage scientists to include both sexes in studies evenly, analyze data separately for males and females, and reevaluate previous studies that lack female representation,” Rowe concluded.
If females are underrepresented, the most effective medications for them may appear ineffective, or the most severe side effects may go undetected.
“The most surprising finding here is not that male and female mice sleep differently, but that no one has really demonstrated this thoroughly until now,” Rowe stated. “We should have known this a long time ago, well before 2024.”
