A report from Modern Medicine Network examines the results of a study that showed that gender makes a difference when it comes to the likelihood of having sleep and wake disturbances.

US and Canadian researchers looked at sex differences in diurnal and circadian variation of sleep and waking while carefully controlling for menstrual cycle phase and hormonal contraceptive use. The diurnal and circadian variation of sleep and alertness of 8 women during 2 phases of the menstrual cycle and 3 women studied during the midfollicular phase were compared with that of 15 men. The participants underwent an ultradian sleep-wake cycle (USW) procedure that consisted of 36 cycles of 60-minute wake episodes alternating with 60-minute nap opportunities. During the wake episodes and naps, core body temperature (CBT), salivary melatonin, subjective alertness, and polysomnographically recorded sleep were measured.

Women had a significant phase advance of CBT but not melatonin rhythms and an advance in diurnal and circadian variation of sleep measures and subjective alertness. Compared with men, they also had increased amplitude of diurnal and circadian variation of alertness, mainly due to a larger decline in nocturnal nadir.

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