Distal skin temperature is reduced in individuals with trait vulnerability to stress-related sleep disturbance

Vulnerability to sleep disturbance following stress (i.e., sleep reactivity) is associated with incident insomnia, though the underlying physiological mechanisms remain unknown. We examined skin temperature stress responsiveness in individuals with high (HSR) versus low (LSR) sleep reactivity. We hypothesized that individuals with HSR would exhibit exaggerated reductions in distal skin temperature during stress. Twenty-eight adults with LSR (5 M/9 F; age: 21 ± 4 yr; BMI: 24 ± 4 kg/m²) and HSR (5 M/9 F; age: 22 ± 4 yr; BMI: 23 ± 3 kg/m²) participated after completing the Ford Insomnia Response to Stress Test (FIRST). Participants wore a water-perfused suit, which was continuously circulated with 34°C water and covered proximal body regions. All participants underwent a Trier Social Stress Test (TSST), which included baseline, speech preparation, speech delivery, and mental arithmetic phases followed by a recovery period. Distal and proximal skin temperature were monitored throughout the testing session. Skin temperature reactivity did not differ between groups. However, a group effect was observed whereby distal skin temperature was reduced by ∼2°C in the HSR compared with the LSR group at all timepoints. Similarly, upper and lower limb distal-proximal gradients (DPGs) were ∼1-2°C lower in the HSR group (i.e., colder extremities). Higher FIRST scores were associated with more negative DPG (<i>r</i> = 0.416-0.578). Despite similar reactivity profiles, individuals with HSR exhibit reduced distal skin temperature, the extent of which was proportional to sleep reactivity severity. These findings suggest that differences in distal skin temperature may be a physiological marker of greater vulnerability to stress-related sleep disturbances in individuals with HSR.<b>NEW & NOTEWORTHY</b> Before sleep, distal skin temperature (i.e., blood flow) increases, facilitating core body temperature reductions that coincide with sleep onset timing. This study investigated whether distal skin temperature at rest and in response to stress differ in individuals with trait susceptibility to stress-related sleep disruption (i.e., high sleep reactivity). Our findings suggest that reduced skin temperature, particularly in distal regions, may represent a physiological marker characterizing interindividual vulnerability to sleep disturbance and insomnia development.