Pain
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The role that inflammation plays in human nerve injury and neuropathic pain is incompletely understood. Previous studies highlight the role of inflammation in the generation and maintenance of neuropathic pain, but the emerging evidence from the preclinical literature for its role in the resolution of neuropathic pain remains to be explored in humans. Here, we use carpal tunnel syndrome (CTS) as a human model system of nerve injury and neuropathic pain to determine changes in serum cytokine protein levels and gene expression levels before (active stage of disease) and after carpal tunnel decompression surgery (recovery). ⋯ By contrast, protein levels of IL-4 positively correlated with pain scores. In conclusion, we demonstrate specific dysregulation of systemic cytokine expression in both the active and resolution phases of nerve injury and neuropathic pain. IL-9 represents an interesting candidate associated with resolution of nerve injury and neuropathic pain.
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Data on the etiological factors underlying the co-occurrence of common adolescent pain with anxiety and depression symptoms are very limited. Opioid prescriptions for adolescent pain problems are on the rise in North America and constitute a risk factor for diversion, misuse, and substance use. In this study, we aimed to investigate the phenotypic and etiological association among pain, depression, and anxiety and to test their link to substance use in adolescents. ⋯ A common phenotypic factor capturing all 3 phenotypes was positively associated (β = 0.19, P < 0.001, confidence interval: 0.10-0.27) with substance use. These findings indicate that several intertwined mechanisms, including genetic factors, can explain a shared liability to common adolescent pain, anxiety, and depression problems. Their association with substance use remains traceable even in societies with relatively low prevalence of opioid prescriptions.
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Cognitive dysfunction is a common fibromyalgia (FM) symptom and can impact on the daily lives of those affected. We investigated whether within-day pain intensity ratings were associated with contemporaneous objective and subjective measures of cognitive function and whether within-day increases in pain intensity preceded increases in cognitive dysfunction or vice versa. Inclusion of a non-FM group allowed us to examine whether effects were specific to FM. ⋯ For the FM group, higher pain was associated with longer processing speed; for the non-FM group, higher pain was associated with shorter processing speed. Pain increase did not precede change in subjective or objective cognitive function in the FM group, but reduction in working memory preceded increase in pain intensity. This finding warrants further research attention and, if replicated, could hold prognostic and/or therapeutic potential.
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Periarticular muscle plays an important role in the pathogenesis of musculoskeletal pain. We recently reported that pain population consists of distinct subgroups of which the causes and mechanisms may differ. This study aimed to examine the association of lean mass, muscle strength, and quality with 10.7-year pain trajectory. ⋯ Greater leg and knee extensor strength and muscle quality were associated with "Mild pain" and "Moderate pain" trajectories (RRR: 0.52-0.65, all P < 0.05). Similar results were found in those with radiographic knee osteoarthritis. Higher lower-limb muscle strength and quality, and relative lean mass, are associated with a reduced risk of severe knee pain trajectories, suggesting that improving muscle function and composition may protect against persistent unfavourable knee pain courses.