Diurnal and circadian variation of sleep and alertness in men vs. naturally cycling women

Abstract

This study quantifies sex differences in the diurnal and circadian variation of sleep and waking while controlling for menstrual cycle phase and hormonal contraceptive use. We compared the diurnal and circadian variation of sleep and alertness of 8 women studied during two phases of the menstrual cycle and 3 women studied during their midfollicular phase with that of 15 men. Participants underwent an ultradian sleep-wake cycle (USW) procedure consisting of 36 cycles of 60-min wake episodes alternating with 60-min nap opportunities. Core body temperature (CBT), salivary melatonin, subjective alertness, and polysomnographically recorded sleep were measured throughout this procedure. All analyzed measures showed a significant diurnal and circadian variation throughout the USW procedure. Compared with men, women demonstrated a significant phase advance of the CBT but not melatonin rhythms, as well as an advance in the diurnal and circadian variation of sleep measures and subjective alertness. Furthermore, women experienced an increased amplitude of the diurnal and circadian variation of alertness, mainly due to a larger decline in the nocturnal nadir. Our results indicate that women are likely initiating sleep at a later circadian phase than men, which may be one factor contributing to the increased susceptibility to sleep disturbances reported in women. Lower nighttime alertness is also observed, suggesting a physiological basis for a greater susceptibility to maladaptation to night shift work in women.sex difference | circadian variation of sleep | circadian variation of alertness | core body temperature | melatonin A meta-analysis has indicated an overall increased risk ratio of 1.41 in women vs. men for experiencing insomnia, and this risk ratio increases to 1.64 when considering high-quality studies with rigorous methodology (1). The etiology of sex-based differences in vulnerability to sleep disturbances remains to be fully elucidated, but evidence points to a role for sex-based differences in sleep, its timing, and circadian rhythms as potential contributors (2).There is sufficient evidence to support a role for circadian factors in the pathophysiology of chronic insomnia, as the timing of sleep relative to the endogenous circadian system can substantially affect sleep initiation and maintenance (3). Interestingly, morphological differences, as well as variations in circulating hormones and their receptors, have been reported between sexes and can affect circadian physiology. For example, the localization of sex steroid receptors to the suprachiasmatic nucleus (SCN) and a sex difference in the expression of androgen and estrogen receptors there indicate a direct and differential role of specific gonadal steroid hormones in the circadian system (4). Moreover, a sexual dimorphism in structure and sex steroid receptor expression also exists in efferent targets of the SCN, including the preoptic area of the hypothalamus, which is known to influence sleep (4). In a recent postmortem brain study, the circadian vari...

Influence of Sleeping Patterns in Health and Academic Performance Among University Students

“…All of these findings are compatible with those provided by previous studies, where women are more likely than men to report more sleep problems and poor sleep quality [58,59]. Similarly, other studies [60] report that, for a similar sleep schedule in men and women, women's chronobiological cycle makes them sleep and wake up before men.…”

0158 Chronotypes in the Us - Influence of Age and Sex

“…Hormonal changes might act as modulators for an aging circadian system, causing a slow-down in women between 35 and 50 (and a speed-up in men aged 55 to 65). Studies examining circadian differences between males and females usually report an earlier phase of core body temperature (CBT) and melatonin rhythms in women than men [34][35][36][37][38]. These studies, conducted with younger subjects (<30yrs), are consistent with our results and previous findings that suggest that women are earlier chronotypes than men during adolescence and early adulthood.…”

Sex differences and the neurobiology of affective disorders

“…Additionally, postmortem studies of men and women with MDD have reported a sex difference in the expression within the dorsolateral prefrontal cortex of multiple glutamatergic genes, with increased expression in women [266]. Finally, several clock genes have been reported to differ in a sex-specific manner, possibly in keeping with reports that women have an overall phase advance in several measures of circadian rhythmicity compared with men [267][268][269].…”