Altered sleep EEG spectral dynamics across the menstrual cycle in premenstrual dysphoric disorder

Premenstrual Dysphoric Disorder (PMDD) is frequently associated with luteal-phase (LP) insomnia. Although the mechanisms underlying insomnia remain unclear, prior evidence suggests paradoxically increased N3 sleep in PMDD across the menstrual cycle. This study investigated potential alterations in sleep microarchitecture in women with PMDD.

Six women diagnosed with PMDD (32.0 ± 5.7years), along with five healthy controls (30.4 ± 8.2 years) completed polysomnographic sleep recordings (PSGs) every third night throughout one menstrual cycle. EEG spectral analysis (C3-A2) was performed on NREM sleep using Fast Fourier Transform with a 4-s Hamming window and 50 % overlap, and a sleep spindle detector was used. Within-group changes were reported relative to the follicular phase (set at 100 %), and between-group differences relative to controls (set at 100 %), with 95 % confidence intervals for significance. Mixed-model ANOVA was used for spindles parameters. Correlations examined the relationships among EEG frequency bands, core body temperature (Tcore), urinary 6-sulfatoxymelatonin (aMT6), and self-reported mood and sleep quality.

Relative to their FP, the PMDD group showed decreased theta and increased spindle frequency activity (SFA) in the LP. Between-group comparisons indicated higher SFA (∼60 %) and spindle density in PMDD across both phases, as well as lower slow wave activity (SWA; ∼40 %). Moreover, SWA correlated with aMT6 and subjective sleep quality, while elevated SFA was associated with Tcore and mood symptoms.

This study revealed alterations in sleep microarchitecture in PMDD, particularly regarding spindle activity and SWA. The previously observed increase in N3 sleep may reflect a compensatory mechanism in response to disrupted homeostatic processes, warranting further investigation into targeted interventions for insomnia in PMDD.