Sleep Reactivity Amplifies the Impact of Pre-Sleep Cognitive Arousal on Sleep Disturbances.

Sleep reactivity-an individual's susceptibility to sleep disruptions due to stress-has been linked to increased insomnia risk. Investigating how sleep reactivity moderates the 'stress → pre-sleep arousal → sleep' pathway may help mitigate sleep disturbances and enhance treatment outcomes. In the present study, full-time university students without sleep disorders completed the Ford Insomnia Response to Stress Test (FIRST), which assesses sleep reactivity. From 264 students, 30 students with the lowest and 30 with the highest FIRST scores were selected for further study. They provided daily actigraphy, Pre-sleep Arousal Scale ratings, pre-sleep heart rate (via an ŌURA ring), and perceived stress scores over 2 weeks. Multilevel moderated mediation analyses were conducted using 800 nights of data to examine within- and between-individual associations. At the within-individual level, days with higher-than-usual perceived stress were associated with reduced total sleep time and increased sleep onset latency (p's < 0.05). These effects were mediated by heightened pre-sleep cognitive arousal (p's < 0.05) but not moderated by the FIRST group. In contrast, between-individual analyses revealed a significant moderation by the FIRST group (p < 0.05). High sleep-reactive individuals reported significantly greater average levels of perceived stress and pre-sleep cognitive arousal, leading to prolonged wakefulness after sleep onset (b = 0.123, Monte Carlo confidence interval [MCCI] = 0.006-0.292), compared to low-reactive sleepers. Overall, on a day-to-day basis, both groups showed increased pre-sleep cognitive arousal and sleep disruptions in response to elevated daily stress. However, between individuals, high sleep reactivity significantly amplified the effect of pre-sleep cognitive (but not physiological) arousal, leading to more pronounced sleep disturbances compared to low-reactive sleepers.