Childhood
- During the first months of life, sleep architecture is similar among men and women, but there are some differences in both quantity and quality of sleep, suggesting that CNS maturation is delayed in male vs female infants
- Sleep differences between men and women during childhood are difficult to capture at this age, potentially because “sleep-wake patterns are influenced by a complex interplay between biological processes and environmental, behavioral, and social factors; however, studies including a systematic review have not demonstrated significant sex differences in sleep among children
- Sex differences in sleep begin to emerge as children approach puberty
- With menarche, increased ovarian function and the cyclical release of estrogen and progesterone affect regulation of the sleep-wake cycle (among many other homeostatic functions, including metabolic systems, cardiovascular, and respiratory systems)
- Sex hormones play an important role in sleep regulation and arousals; they may also impact the outcomes of sleep conditions
- Interestingly, gonadectomy in female and male rats “eliminates all sex differences in the sleep-wake cycle; adding back physiological levels of sex-specific steroids restores these differences.”
- Progesterone in particular improves sleep duration and quality, mainly by improving slow wave sleep (SWS) and slow wave activity; elevated prolactin levels seen in lactating women are also associated with increased slow wave sleep.
- Enhanced slow wave sleep due to prolactin, especially in the context of an abrupt withdrawal of estrogen and progesterone following parturition, presents “another important factor to support breastfeeding women in the postnatal period.”
- Progesterone’s impact on sleep goes beyond changes in sleep architecture: as a ventilatory drive stimulant, progesterone increases the activity of the genioglossus muscle involved in dilating the upper airway; one study in 11 healthy women lacking sleep disturbances demonstrated lower upper airway resistance during the luteal phase vs the follicular phase (recall: progesterone levels rise due to secretion by the corpus luteum during the luteal phase)