Thermoregulatory Response to Evening Stress in Individuals with Stress-Induced Insomnia Susceptibility

An increase in distal skin temperature before bedtime facilitates a reduction in core body temperature that contributes to sleep initiation. Psychological stress can disrupt this thermoregulatory process by reducing distal skin temperature, potentially leading to sleep disturbances. Individuals with stress-induced insomnia susceptibility may be particularly vulnerable, yet the thermoregulatory response to stress in these individuals has not been characterized. The aim of this study was to investigate the thermoregulatory response to evening stress in individuals with high versus low insomnia susceptibility. We hypothesized that increased insomnia susceptibility would correspond with an exaggerated reduction in distal skin temperature in response to stress. 28 healthy adults were separated into high (5 males, 9 females, 22±4 years, 23±3 kg/m 2 ) versus low (5 males, 9 females, 21±4 years, 24±4 kg/m 2 ) stress-induced insomnia susceptibility based on the validated Ford Insomnia Response to Stress Test (FIRST). All participants underwent an evening Trier Social Stress Test (TSST), which consisted of a resting baseline (10 min), nonverbal speech preparation (5 min), speech delivery (5 min), mental arithmetic (5 min) and recovery (5 min). Throughout the task, participants wore a water-perfused suit that maintained a thermoneutral state of 34°C. Skin temperature was assessed at both proximal and distal regions. The distal-proximal gradient (DPG) was calculated in each participant across the TSST. A group effect was observed whereby individuals with higher stress-induced insomnia susceptibility exhibited more negative DPG (i.e., colder distal extremities) at each phase of the TSST (p<0.05). Insomnia susceptibility was negatively correlated with the DPG during each phase of the TSST. For the upper limb DPG, correlations were observed across the baseline (r=-0.566, p=0.002), preparation (r=-0.544, p=0.003), speech (r=-0.579, p=0.001), math (r=-0.683, p<0.001), and recovery (r=-0.662, p<0.001) phases. Similarly, lower limb DPG showed significant negative correlations throughout the baseline (r=-0.416, p=0.028), preparation (r=-0.420, p=0.026), speech (r=-0.416, p=0.028), math (r=-0.424, p=0.024), and recovery (r=-0.430, p=0.022) phases. The findings suggest that individuals with higher stress-induced insomnia susceptibility exhibit a significant reduction in distal-proximal gradient (DPG) during all phases of the TSST. This exaggerated thermoregulatory response to multiple laboratory assessments of psychological stress in the distal extremities may contribute to the disrupted sleep patterns observed in this population when exposed to stress and may underly a greater vulnerability to stress-induced insomnia development. Sleep Research Society Foundation This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.