Context: Most studies show sleep homeostasis and continuity remain stable across the menstrual cycle in young women. The influence of the menstrual cycle on physiological sleep in midlife women is unknown.
Objective: The objective of the study was to assess the impact of menstrual cycle phase on the polysomnogram and electroencephalographic (EEG) features of sleep in midlife women, accounting for the presence of an insomnia disorder.
Design and participants: This was a laboratory study of 20 women in the early menopausal transition (48.8 ± 2.9 y), 11 with a Diagnostic and Statistical Manual of Mental Disorders, fourth edition, diagnosis of insomnia, studied on one night each in the follicular and luteal menstrual cycle phases.
Main outcome measures: Polysomnographic and sleep EEG indices were measured.
Results: Both groups of women had more awakenings (P = .003) and arousals (P = .025) per hour of sleep and less percentage slow wave sleep (P = .024) when progesterone was raised (≥3 ng/mL(-1)) during the luteal compared with the follicular phase. Both groups had greater spindle density (P = .007), longer spindles (P = .037), and increased 14-17 Hz EEG activity in the luteal phase (P < .05), although for the 15- to 16-Hz bin, this effect was significant only in women without insomnia (P < .001). Women with insomnia had a shorter sleep duration (P = .012), more wakefulness after sleep onset (P = .031), and a lower sleep efficiency (P = .034) than women without insomnia, regardless of menstrual cycle phase.
Conclusion: Sleep is more disrupted in the luteal phase compared with the follicular phase in midlife women, whether or not they have an insomnia disorder. There is a prominent increase in sleep spindles and spindle frequency activity in the luteal phase, likely an effect of progesterone and/or its neuroactive metabolites acting on sleep regulatory systems.