Subjective Socioeconomic Status Moderates How Resting Heart Rate Variability Predicts Pain Response

Higher resting heart rate variability (HRV)-an index of more flexible response to environmental stressors, including noxious stimuli-has been linked to reduced perception of experimentally induced pain. However, as stress responses are adapted to one's chronic environments, we propose that chronic exposure to threats captured by one's subjective socioeconomic status (SSS) may shape different adaptations that produce distinct pain responses linked to higher resting HRV. Specifically, lower SSS individuals with more threat exposures may prioritize threat detection by upregulating sensitivity to stressors, such as acute pain. Therefore, higher HRV would predict greater perceived acute pain among lower SSS individuals. In contrast, higher SSS individuals with less threat exposures may instead prioritize affective regulation by downregulating sensitivity to stressors, producing lower pain perception with higher HRV. We examined this stress response moderation by SSS in 164 healthy young adults exposed to experimental pain via the cold pressor test (CPT). Resting HRV, indexed by the root-mean-square of successive differences in heart rate, and self-reported SSS were measured at rest. Pain perception indexed by self-reported pain and pain tolerance indexed by hand-immersion time during the CPT were assessed. Results revealed that among higher SSS individuals, higher resting HRV predicted lower pain reports and subsequently greater pain tolerance during the CPT. Conversely, among lower SSS individuals, higher resting HRV predicted higher pain reports and subsequently lower pain tolerance. These findings provide preliminary evidence that environmental stress exposures linked to one's SSS may shape unique biological adaptations that predict distinct pain responses.