The yin and yang of sleep-wake regulation: gender gap in need for sleep persists across the human lifespan.

Purpose: Experiments on sleep regulation under the condition of self-selected light-dark and wake-sleep cycle revealed a larger sleep fraction in women than men. In questionnaire studies, women usually report a greater need for sleep than men. They also sleep more than men in overall and at most life course stages. However, much of the gap was explained by work/family responsibilities and gendered time tradeoffs. We tested whether females from childhood to late adulthood spend longer time in bed than males on weekends, and whether on weekdays, their time in bed fails to become longer due to the socially rather than biologically governed earlier weekday wake ups.

Methods: A set of 340 paired subsamples of male and female sleep times was analyzed. The averaged sleep times were calculated and simulated.

Results: Female-male difference in weekend time in bed attained the value of 0.26 h (the 0.16-h earlier bedtime was combined with the 0.10-h later risetime). The gender gap in weekday risetime was non-significant and the direction of gender difference in weekday time in bed was inconsistent across the lifespan. Model-based simulations provided support for the prediction that the male-female gap in sleep desire can reflect a higher level of sleep slow-wave activity (SWA) in females found in the vast majority of published studies.

Conclusion: Since SWA is strongly indicative of age and age-associated change in neuronal networks, the persistency of female's greater desire for sleep can be explained by the underlying sex difference in age-associated structural changes in these networks.