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In a groundbreaking study by researchers at the University of Colorado Boulder, females have been shown to sleep less, awaken more frequently, and experience less restorative sleep than males. Published in Scientific Reports, the findings could reshape medical research by highlighting the significance of biological factors in sleep differences between sexes.
Biological Roots of Sleep Differences
“Traditionally, differences in sleep patterns between men and women have been attributed to lifestyle factors like caregiving responsibilities,” said Rachel Rowe, senior author and assistant professor of integrative physiology. “Our study suggests biology plays a far more substantial role than previously recognized.”
Using advanced monitoring technology, researchers examined the sleep patterns of 267 C57BL/6J mice, a common strain used in biomedical research. Male mice slept an average of 670 minutes daily—roughly an hour more than females. Importantly, this extra rest occurred during non-Rapid Eye Movement (NREM) sleep, a critical phase for bodily repair and recovery. Female mice, meanwhile, experienced shorter and more fragmented sleep bouts.
Similar patterns have been observed in other species, including rats, birds, and zebrafish, suggesting an evolutionary basis. “Females may be biologically attuned to more sensitive sleep, likely to respond to environmental stimuli crucial for caregiving roles,” Rowe explained.
Implications for Biomedical Research
The study raises critical questions about the validity of decades of research. Historically, male subjects have dominated animal studies, potentially skewing data used to develop treatments and drugs.
“Failing to account for sex differences in sleep behaviors can lead to flawed interpretations,” said lead author Grant Mannino, who emphasized the necessity of including both sexes in preclinical studies. Simulations from the study revealed that treatments effective for females were only accurately assessed when research populations included equal numbers of males and females.
This oversight has implications for drug efficacy and safety. Treatments tailored to female biology may be dismissed as ineffective, while side effects specific to females could go unnoticed. “The pipeline from bench to bedside takes decades. Is it so long because sex differences are underappreciated?” asked Rowe.
Progress and Future Directions
While initiatives like the National Institutes of Health’s 2016 policy requiring sex consideration in animal studies have pushed for greater balance, sex bias persists in research. The authors advocate for analyzing male and female data separately and re-evaluating studies that neglected female subjects.
“The surprising takeaway isn’t just that males and females sleep differently,” said Rowe. “It’s that this hasn’t been thoroughly investigated until now.”
The findings urge a reevaluation of past research and underscore the need for gender-inclusive studies in the quest for more effective, personalized medicine.
Reference:
Grant S. Mannino et al., The importance of including both sexes in preclinical sleep studies and analyses, Scientific Reports (2024). DOI: 10.1038/s41598-024-70996-1
