0418 One-Month Stability in Insomnia Sleep Metrics

Abstract Introduction Night-to-night variability in sleep is a hallmark of insomnia, but it remains unclear whether subjective and objective sleep metrics maintain consistent relative differences across longer timescales. We conducted a preliminary analysis in an ongoing study to examine one-month stability in subjective and objective sleep indices in individuals with insomnia symptoms. Methods Twenty-four participants with insomnia symptoms (62.5% female; mean age = 37.0 ± 7.0 years) completed two nights of at-home polysomnography (PSG) with a one-month interval. Two-week sleep diaries and self-report questionnaires were collected at both points. Macro-architectural features (e.g., sleep onset latency (SOL), wake after sleep onset (WASO), total sleep time (TST), sleep stage percentages, REM latency) were derived from auto-staged PSG using the YASA algorithm based on a single electroencephalography (EEG) and electrooculography (EOG) pair. Group mean differences across time points were tested using paired t-tests. Rank-order stability was examined using intraclass correlations (ICCs). Results ISI scores (t(23) = 3.62, p = 0.001) and several sleep stage measures changed significantly across time points (%N1: t(23) = 2.95, p = 0.007, %N2: t(23) = 2.42, p = 0.02, %REM: t(23) = -2.69, p = 0.01), whereas sleep diary indices and PSG-derived SOL, WASO, and TST showed no mean-level change. Rank-order stability estimates were moderate to high across subjective and objective measures (ICC = 0.55–0.81), except for subjective SOL and PSG-derived SOL/WASO (ICC < 0.40). Conclusion Subjective insomnia severity changed over one month, whereas quantitative sleep continuity metrics from both subjective and objective sources remained stable. In contrast, sleep architecture shifted significantly across time points. Despite these mean-level discrepancies, individuals retained their relative standing over time across both subjective and objective measures, suggesting a persistent component of insomnia. Future work should determine whether microstructural sleep features or subtype-specific physiology more accurately capture clinically relevant instability in insomnia. Support (if any)