Disrupted fear regulation in insomnia disorder revealed by arousal estimation from skin conductance

Insomnia disorder (ID) is a common sleep-wake disorder marked by persistent dissatisfaction with sleep quality or quantity. Previous studies have shown that sleep plays a critical role in emotion regulation, particularly in fear extinction. This study aims to characterize ID using estimates of the sympathetic arousal state derived from skin conductance (SC)-based observations, and to compare two observation models: the marked point process (MPP) model and the MPP coupled with continuous (MPP+Cont) model. We utilize SC data from a fear conditioning and extinction procedure involving 24 individuals with ID and 24 good sleepers (GS). The SC measurements are deconvolved to extract autonomic nervous system (ANS) activations and the tonic component. The MPP observation model uses only the extracted ANS activations, while the MPP+Cont model incorporates both ANS activations and the tonic component. Both models are employed to estimate the underlying arousal state over time and compute a high arousal index (HAI). We compare the estimated arousal states and HAI between the ID and GS groups to assess alterations in arousal associated with ID. Our results reveal that ID may be associated with impaired fear extinction learning and recall. Notably, the distinction between ID and GS emerges only under the MPP+Cont model, indicating the critical role of the tonic component in arousal estimation. Overall, this study highlights the potential of arousal state estimation for understanding autonomic dysregulation in ID, thereby supporting interventions for fear-centered comorbidities and improving quality of life.