Is Resolution of Chronic Pain Associated With Changes in Blood Pressure-related Hypoalgesia?

Background In healthy individuals, elevated resting blood pressure (BP) is associated with reduced pain responsiveness and lower temporal summation. Prior work indicates that this BP-related hypoalgesia is reduced in individuals with chronic pain. Purpose This study evaluated whether resolution of chronic pain was associated with greater BP-related hypoalgesia compared to nonresolution. Methods From a prospective sample of adolescents and young adults diagnosed with chronic functional abdominal pain an average of 9 years earlier, 99 individuals in whom the condition had resolved and 51 individuals with ongoing abdominal pain were studied. Resting systolic BP was assessed, followed by evaluation of thermal pain threshold and tolerance, and assessment of temporal summation to thermal pain stimuli. Results Higher resting systolic BP was significantly associated with higher pain threshold and tolerance, and lower temporal summation only in the group with resolved functional abdominal pain (p<.05). Hierarchical regressions revealed that interactions between BP and resolution of chronic pain were significant only for pain tolerance (p<.05). Analyses by sex indicated that interactions between BP and resolution status were significant for the temporal summation outcome in males but not in females. Conclusions Results suggest that BP-related hypoalgesic mechanisms may be more effective in individuals in whom chronic pain has resolved compared to those with ongoing chronic pain. Findings hint at sex differences in the extent to which resolution of chronic pain is associated with BP-related hypoalgesia. Whether greater BP-related hypoalgesia is a consequence of, or alternatively a contributor to, resolution of chronic pain warrants further investigation.