The relationship between stress and sleep quality: An intensive longitudinal study

Both stress and poor sleep quality can undermine long-term health. Stress has been shown to disrupt sleep, while poor sleep may increase stress reactivity, compounding their impact on health. Few studies have captured bidirectional dynamics of stress and sleep in daily life using subjective and objective measures. In this 7-day intensive longitudinal study, 106 participants (age: M = 22.65, SD = 3.01; 85.8% female) reported daily and momentary perceived stress and sleep quality, while wearable sensors recorded heart rate variability and derived objective sleep indicators ( n = 742 days). Data were analyzed using Bayesian cross-lagged multilevel models. At the within-person level, better-than-usual subjective sleep quality was related to lower next-day perceived stress. At the between-person level, higher perceived stress was related to worse subjective sleep quality and longer sleep onset latency. Findings for objective sleep quality indicators depended on how nocturnal timeframes were operationalized (i.e., self-reported, accelerometry-based, or fixed time windows), with inconsistent associations for sleep onset latency. Findings show that stress–sleep associations differ within and between persons, across subjective and objective sleep indicators, and by operationalization of nocturnal timeframes. Future studies should carefully consider measurement decisions and explore underlying mechanisms to better understand stress-sleep relationships in daily life.