Mediators of the association between childhood trauma and pain sensitivity in adulthood: a Multidisciplinary Approach to the Study of Chronic Pelvic Pain Research Network analysis

Latent bladder hypersensitivity induced by neonatal cystitis in rats unmasked by segmental but not hetero-segmental inflammation

Rats which experienced neonatal bladder inflammation (NBI) have been demonstrated to exhibit latent bladder hypersensitivity with a nociceptive component that becomes unmasked by a second inflammatory insult as an adult. Manifested as augmented reflex and neuronal responses to urinary bladder distension (UBD), these NBI-induced changes are revealed by using inflammation of nearby structures as an adult pretreatment. The effect of inflammation in distant structures is not known. These studies examined visceromotor reflex responses and lumbosacral spinal dorsal horn neuronal responses to UBD in rats and compared effects of segmental (hindpaw) versus hetero-segmental (forepaw or face) inflammatory pretreatments in 192 female Sprague-Dawley rats raised from birth. On postnatal days 14-16 these rats underwent either NBI or control procedures. As adults, these rats received control injections or 0.1 ml Complete Freund's Adjuvant (CFA) injections into one of four sites. Three days later they were studied in reflex or spinal single-cell neuronal experiments where responses were evoked by UBD. Visceromotor responses to UBD were more robust in rats which had injections in the hindpaw (either side) but were not significantly affected by forepaw or facial injections. Similar results were identified in L6/S1 neurons with more robust UBD-evoked responses observed in rats receiving hindpaw CFA injections but not forepaw injections. These results indicate that latent bladder hypersensitivity induced by NBI is made manifest by segmental, but not hetero-segmental inflammatory stimuli. This observation correlates with pain in patients with interstitial cystitis who often have flares in symptoms associated with inflammation of nearby structures.

Adverse childhood experience is associated with an increased risk of reporting chronic pain in adulthood: a stystematic review and meta-analysis

Background: Adverse childhood experiences (ACEs) have been shown to negatively affect health in adulthood. Estimates of associations between ACEs and chronic painful conditions are lacking.Objectives: This systematic review and meta-analysis aimed to evaluate associations between exposure to ACEs and chronic pain and pain-related disability in adults.Methods: We searched 10 electronic databases from inception to February 2023. We included observational studies assessing associations between direct ACEs (childhood sexual, physical, emotional abuse, or neglect) alone or in combination with indirect ACEs (witnessing domestic violence, household mental illness), and adult chronic pain (≥3 months duration) and pain-related disability (daily activities limited by chronic pain). Pairs of reviewers independently extracted data and assessed study risks of bias. Random-effect models were used to calculate pooled adjusted odds ratios [aOR]. Tau square [T2], 95% prediction intervals [95%PI] and I2 expressed the amount of heterogeneity, and meta-regressions and subgroup meta-analyses investigated sources of heterogeneity (PROSPERO: CRD42020150230).Results: We identified 85 studies including 826,452 adults of which 57 studies were included in meta-analyses. Study quality was generally good or fair (n = 70). The odds of reporting chronic pain in adulthood were significantly higher among individuals exposed to a direct ACE (aOR, 1.45, 95%CI, 1.38-1.53). Individuals reporting childhood physical abuse were significantly more likely to report both chronic pain (aOR, 1.50, 95CI, 1.39-1.64) and pain-related disability (1.46, 95CI, 1.03-2.08) during adulthood. Exposure to any ACEs alone or combined with indirect ACEs significantly increase the odds of adult chronic painful conditions (aOR, 1.53, 95%CI, 1.42-1.65) and pain-related disability (aOR, 1.29; 95%CI, 1.01-1.66). The risk of chronic pain in adulthood significantly increased from one ACE (aOR, 1.29, 95%CI, 1.22-1.37) to four or more ACEs (1.95, 95%CI, 1.73-2.19).Conclusions: Single and cumulative ACEs are significantly associated with reporting of chronic pain and pain-related disability as an adult.