0221 Dynamic and Stable Associations Between Multidimensional Sleep and Cardiovascular Physiology: Evidence From a 27-Month Longitudinal Cohort

Abstract Introduction Sleep duration, timing, and consistency each influence cardiovascular physiology, yet their independent and interactive contributions remain unclear. Prior research links short, mistimed, or irregular sleep to higher resting heart rate (RHR) and lower heart rate variability (HRV), but few studies have evaluated nightly deviations, stable between-person differences, and long-term changes simultaneously. This study examined how multidimensional sleep patterns relate to nocturnal cardiovascular function and multi-year physiological trajectories in free-living individuals. Methods Participants (N = 8,388) were monitored for 27 months (April 2023–June 2025) with a validated biometric device that provided objective sleep metrics, including duration, midsleep timing, and sleep consistency (day-to-day regularity of sleep–wake timing), alongside nightly RHR and HRV. Generalized additive mixed models assessed between-person (participant-level averages) and within-person (nightly deviations from 28-day rolling means) associations between sleep measures and nocturnal RHR and HRV, adjusting for age, gender, body mass index, average and daily physical activity, seasonality, weekday, and auto-correlated errors. Weekly aggregated models evaluated whether two-year changes in sleep dimensions predicted long-term cardiovascular trajectories. Results Between participants, greater sleep consistency correlated with lower RHR, even after controlling for sleep duration and timing (p .001), whereas longer sleep duration correlated with higher HRV (p .001). Within participants, sleeping shorter-than-usual or later-than-usual correlated with higher RHR and lower HRV, whereas sleeping longer-than-usual or earlier-than-usual showed the opposite (ps .001). Nightly changes in sleep consistency did not predict changes in RHR or HRV. Two-year trajectory models demonstrated that favorable changes in sleep (i.e., greater consistency, longer duration, and earlier timing) aligned with progressive improvements in cardiovascular physiology, reflected by decreasing RHR and increasing HRV across the same period. In contrast, participants whose sleep patterns worsened exhibited parallel physiological declines. Conclusion Sleep duration, timing, and consistency each demonstrate distinct relationships with nocturnal cardiovascular physiology. Sleep consistency emerges as the strongest predictor of between-person RHR and long-term cardiovascular trajectories, whereas nightly deviations in duration and timing were most strongly associated with short-term fluctuations in RHR and HRV. These results suggest effective sleep interventions may benefit from emphasizing long-term consistency while also managing nightly deviations in duration and timing to support cardiovascular health. Support (if any)