The phenotypic and genetic signatures of common musculoskeletal pain conditions

General and Pain-Associated Psychological Distress Phenotypes Among Patients With Low Back Pain in the Military Health System

OBJECTIVE

The primary objective was to describe rates of general and pain-related psychological distress for individuals with low back pain (LBP) in the Military Health System (MHS). We identified common phenotypes defined by rates of general and pain-related psychological distress and compared phenotypes on their level of pain interference, physical function, anxiety, and depression.

METHODS

We created a cohort from two completed trials assessing nonpharmacological treatment for LBP in the MHS (n = 510 total). The Optimal Screening for Prediction of Referral and Outcome Yellow Flag assessment tool identified the presence of 11 different yellow flags. Latent class analysis (LCA) used yellow flag indicators to identify common psychological phenotypes. We then compared Patient-Reported Outcomes Measurement Information Systems measures of pain interference, physical function, sleep disturbance, depression, and anxiety across phenotypes.

RESULTS

LCA identified five phenotypes (percentage of the sample): low distress (32%), high distress (27%), poor pain coping and low self-efficacy (18%), low self-efficacy and acceptance (14%), and poor pain coping (10%). Highly distressed phenotypes reported higher levels of pain interference, sleep disturbance, depression, and anxiety than those with other phenotypes, whereas the low distress phenotype had significantly lower pain interference and higher physical function scores than those characterized by all other phenotypes.

CONCLUSION

These phenotypes provide opportunities for clinicians and researchers to develop novel LBP treatment pathways tailored to patients with different profiles of psychological distress. Future work is needed to validate their predictive capabilities for clinical outcomes.

Multimodal benefits of hypnosis on pain, mental health, sleep, and quality of life in patients with chronic pain related to fibromyalgia: A randomized, controlled, blindly-evaluated trial

BACKGROUND AND PURPOSE

Fibromyalgia is a chronic syndrome marked by intense musculoskeletal pain often refractory to pharmacological treatment. Although studies have shown that hypnosis improves fibromyalgia pain, gaps in experimental design limit their reliability. This work aimed to evaluate the effects of hypnosis on pain, mental health, sleep, and quality of life in participants with fibromyalgia chronic pain.

METHODS

In this prospective, parallel, randomized, controlled, blindly-evaluated trial, participants of both sexes (n = 49) diagnosed with fibromyalgia and with moderate to severe chronic pain attended 8 weekly 1-h sessions with a hypnotherapist. For the hypnosis group (n = 24), sessions consisted in induction of hypnotic trance followed by suggestions to promote analgesia. For the control group (n = 25), sessions consisted in casual unscripted conversation. Participants were assessed at baseline (7 days before), post-intervention (7 days after), and follow-up (3 months after). The primary outcome was pain intensity. The secondary outcomes were the sensory and affective dimensions of pain; pain unpleasantness; pain catastrophizing; anxiety and depression; sleep quality; fibromyalgia impact; and quality of life.

RESULTS

Hypnosis significantly reduced pain scores both at post-intervention and follow-up in comparison with baseline. The analgesic effect of hypnosis combined with pharmacological treatment lasted for at least 3 months and was superior to analgesia promoted by first- and second-line pharmacological treatment alone. Hypnosis significantly improved all parameters evaluated as secondary outcomes both at post-intervention and follow-up without inducing adverse events.

CONCLUSION

Our results corroborate that clinical hypnosis is an effective and feasible tool for managing chronic pain and other symptoms of fibromyalgia.

Deciphering nociplastic pain: clinical features, risk factors and potential mechanisms

Nociplastic pain is a mechanistic term used to describe pain that arises or is sustained by altered nociception, despite the absence of tissue damage. Although nociplastic pain has distinct pathophysiology from nociceptive and neuropathic pain, these pain mechanisms often coincide within individuals, which contributes to the intractability of chronic pain. Key symptoms of nociplastic pain include pain in multiple body regions, fatigue, sleep disturbances, cognitive dysfunction, depression and anxiety. Individuals with nociplastic pain are often diffusely tender - indicative of hyperalgesia and/or allodynia - and are often more sensitive than others to non-painful sensory stimuli such as lights, odours and noises. This Review summarizes the risk factors, clinical presentation and treatment of nociplastic pain, and describes how alterations in brain function and structure, immune processing and peripheral factors might contribute to the nociplastic pain phenotype. This article concludes with a discussion of two proposed subtypes of nociplastic pain that reflect distinct neurobiological features and treatment responsivity.

Comparative analysis of centrally mediated and inflammatory pain experiences amongst patients diagnosed with rheumatoid arthritis: A multimethods study

BACKGROUND

The identification of pain originating from distinct biological processes may lead to individualised pain treatment. In this study, we aimed to explore the pain experiences of patients with rheumatoid arthritis (RA), differentiating between those predominantly exhibiting features of peripheral inflammatory versus centrally mediated pain.

METHODS

Through a multimethods approach we (i) quantitatively analysed the differences in pain descriptors between patients diagnosed with RA experiencing peripheral inflammatory and centrally mediated pain, utilising the Short Form-McGill Pain Questionnaire which includes the pain visual analogue scale (VAS) and (ii) qualitatively explored their subjective pain experiences grounded in the biopsychosocial model, commonly applied in chronic pain.

RESULTS

Participants with centrally mediated pain reported higher pain scores on the VAS, used a wider range of pain descriptors, and a higher proportion selected each descriptor compared to those with inflammatory pain (p < .001). The qualitative analysis revealed the centrally mediated pain group's experiences were overwhelming and relentless, struggling to precisely articulate the nature of their pain. In contrast, individuals with inflammatory pain expressed their pain in more tangible terms and shared their adaptive and coping strategies. Importantly, both groups revealed the substantial psychological, functional and social impacts of their pain, highlighting the often 'invisible' and misunderstood nature of their symptoms.

CONCLUSION

This study has gained a deeper insight into the pain experiences of patients living with RA, particularly in differentiating between centrally mediated and inflammatory types of pain, potentially facilitating a more individualised approach to pain treatment.

PATIENT CONTRIBUTION

Patients actively participated in the study conception and design. This engagement includes collaboration with key stakeholders, such as members of the National Rheumatoid Arthritis Society and Patient Research Partners (PRPs), who provided continuous feedback and guidance throughout the research process. Specifically, the qualitative element was coproduced with two PRPs, who were involved in co-leading the focus groups and data analysis.

Examining the Association Between Objective Physical Activity and Momentary Pain: A Systematic Review of Studies Using Ambulatory Assessment

Chronic pain (CP) is a debilitating and increasingly common health condition that adversely impacts function, including physical activity (PA). Research using ambulatory assessment (AA) methods (eg, ecological momentary assessment, actigraphy) offers promise for elucidating the relationship between momentary pain and objective PA in CP populations. This study aimed to systematically review articles assessing the association between momentary pain and PA in adults with CP as measured using AA and to make recommendations for the measurement and study of this relationship. Five databases were systematically searched, and 13 unique records (N = 768) met the inclusion criteria. CP conditions included mixed/nonspecific CP (k = 3), low back pain (k = 2), fibromyalgia (k = 1), unspecified arthritis (k = 1), and hip/knee osteoarthritis (k = 6). The average age of participants across studies was 55.29 years, and the majority identified as women (60.68%) and White (83.16%). All studies measured objective PA via actigraphy, and momentary pain with either a diary/log or ratings on an actigraph. Studies varied in the quantification of PA (ie, activity counts, step count, moderate-vigorous PA), statistical method (ie, correlation, regression, multilevel modeling), and inclusion of moderators (eg, pain acceptance). Studies reported mixed results for the pain-PA relationship. This heterogeneity suggests that no summarizing conclusions can be drawn about the pain-PA relationship without further investigation into its complex nuances. More within-person and exploratory examinations that maximize the richness of AA data are needed. A greater understanding of this relationship can inform psychotherapeutic and behavioral recommendations to improve CP outcomes. PERSPECTIVE: This article presents a systematic review of the literature on the association between momentary pain and PA in adults with CP as measured using AA methods. A better understanding of this nuanced relationship could help elucidate areas for timely intervention and may inform clinical recommendations to improve CP outcomes. PROSPERO REGISTRATION NUMBER: CRD42023389913.

Pain mechanisms for the practicing rheumatologist

Pain in rheumatic diseases transcends the traditional nociceptive paradigm, incorporating complex interactions between nociceptive, neuropathic, and nociplastic mechanisms, as well as significant psychosocial factors. Advances in understanding chronic pain highlight the role of peripheral and central sensitization, and the emergence of nociplastic pain-a result of altered central nervous system processing. This modern perspective acknowledges the influence of mood disorders, environmental stressors, and cognitive patterns like catastrophizing, revealing the intricate interplay between biological, psychological, and social determinants of pain. Research emphasizes the brain's pivotal role in pain perception, underscoring the importance of comprehensive approaches that integrate medical, psychological, and social interventions to address the multifaceted nature of chronic pain in rheumatic diseases effectively.

COMT and SCN9A gene variants do not contribute to chronic low back pain in Mexican-Mestizo patients

BACKGROUND

Chronic low back pain (CLBP) is a complex condition in which genetic factors play a role in its susceptibility. Catechol-O-methyltransferase (COMT) and sodium channel NaV1.7 (SCN9A) genes are implicated in pain perception. The aim is to analyze the association of COMT and SCN9A with CLBP and their interaction, in a Mexican-Mestizo population.

METHODS

A case-control study was conducted. Cases corresponded to adults of both sexes with CLBP. Controls were adults with no CLBP. Variants of SCN9A and COMT were genotyped. Allelic and genotypic frequencies and Hardy-Weinberg equilibrium (HWE) were calculated. Association was tested under codominant, dominant, and recessive models. Multifactor dimensionality reduction was developed to detect epistasis.

RESULTS

Gene variants were in HWE, and there was no association under different inheritance models in the whole sample. In women, in codominant and dominant models, a trend to a high risk was observed for AA of rs4680 of COMT (OR = 1.7 [0.5-5.3] and 1.6 [0.7-3.4]) and for TT of rs4633 (OR = 1.6 [0.7-3.7] and 1.6 [0.7-3.4]). In men, a trend to low risk was observed for AG genotype of rs4680 in the same models (OR = 0.6 [0.2-1.7] and 0.7 [0.3-1.7]), and for TC genotype of rs4633 in the codominant model (OR = 0.6 [0.2-1.7]). In the interaction analysis, a model of the SCN9A and COMT variants showed a CVC of 10/10; however, the TA was 0.4141.

CONCLUSION

COMT and SCN9A variants are not associated with CLBP in the analyzed Mexican-Mestizo population.

The association of gene polymorphisms in catechol-O'methyltransferase (COMT) and β2-adrenergic receptor (ADRB2) with temporomandibular joint disorders

OBJECTIVE

Temporomandibular disorder (TMD) has a multifactorial etiology that includes environmental, psychological, and genetic factors. This study aimed to evaluate the possible relationship between polymorphisms in Catechol-O-methyltransferase (COMT) and β2-adrenergic receptor (ADRB2) genes with TMD.

DESIGN

This observational case-control study included 80 patients and 70 healthy controls. The diagnosis of TMD was made using the diagnostic criteria for TMD and the following TMD categories were used for the case group: muscular TMD and articular TMD (disc displacement and arthralgia). A genotyping study of gene polymorphisms in COMT (rs 9332377) and ADRB2 (rs20530449) was performed from genomic DNA isolated from blood. The chi-square test was used to analyze the relationships. P < 0.05 was accepted as a significant difference.

RESULTS

The polymorphic TT and CT genotype for COMT (rs rs9332377) was significantly higher in the articular TMD group while the non-polymorphic CC genotype was significantly lower in the articular TMD group (P < 0.05). Regarding ADRB2 (rs20530449), the polymorphic GG genotype was similarly considerably more common in the articular TMD group (p < 0.05). In addition, the T allele in the COMT (rs rs9332377) gene was found to be significantly higher in the articular TMD group (p < 0.05).

CONCLUSIONS

In the Turkish population, gene polymorphisms in COMT (rs9332377) and ADRB2 (rs2053044) were associated with articular TMD. This study supports the hypothesis that changes in COMT and ADRB2 genes may play a role in temporomandibular joint pain and predisposition to TMD.

Pain-sensorimotor interactions: New perspectives and a new model

How pain and sensorimotor behavior interact has been the subject of research and debate for many decades. This article reviews theories bearing on pain-sensorimotor interactions and considers their strengths and limitations in the light of findings from experimental and clinical studies of pain-sensorimotor interactions in the spinal and craniofacial sensorimotor systems. A strength of recent theories is that they have incorporated concepts and features missing from earlier theories to account for the role of the sensory-discriminative, motivational-affective, and cognitive-evaluative dimensions of pain in pain-sensorimotor interactions. Findings acquired since the formulation of these recent theories indicate that additional features need to be considered to provide a more comprehensive conceptualization of pain-sensorimotor interactions. These features include biopsychosocial influences that range from biological factors such as genetics and epigenetics to psychological factors and social factors encompassing environmental and cultural influences. Also needing consideration is a mechanistic framework that includes other biological factors reflecting nociceptive processes and glioplastic and neuroplastic changes in sensorimotor and related brain and spinal cord circuits in acute or chronic pain conditions. The literature reviewed and the limitations of previous theories bearing on pain-sensorimotor interactions have led us to provide new perspectives on these interactions, and this has prompted our development of a new concept, the Theory of Pain-Sensorimotor Interactions (TOPSMI) that we suggest gives a more comprehensive framework to consider the interactions and their complexity. This theory states that pain is associated with plastic changes in the central nervous system (CNS) that lead to an activation pattern of motor units that contributes to the individual's adaptive sensorimotor behavior. This activation pattern takes account of the biological, psychological, and social influences on the musculoskeletal tissues involved in sensorimotor behavior and on the plastic changes and the experience of pain in that individual. The pattern is normally optimized in terms of biomechanical advantage and metabolic cost related to the features of the individual's musculoskeletal tissues and aims to minimize pain and any associated sensorimotor changes, and thereby maintain homeostasis. However, adverse biopsychosocial factors and their interactions may result in plastic CNS changes leading to less optimal, even maladaptive, sensorimotor changes producing motor unit activation patterns associated with the development of further pain. This more comprehensive theory points towards customized treatment strategies, in line with the management approaches to pain proposed in the biopsychosocial model of pain.

How Do Spinal Parameters Change in Patients Who Have Improvement of Low Back Pain After Total Hip Arthroplasty? A Propensity Score-Matched Cohort Study

BACKGROUND

Many studies have demonstrated that low back pain (LBP) improves after total hip arthroplasty (THA). However, the mechanism underlying this improvement remains unclear. We aimed to investigate changes in the spinal parameters of patients who had LBP improvement after THA to elucidate the mechanism of LBP improvement.

METHODS

We included 261 patients who underwent primary THA between December 2015 and June 2021 and had a preoperative visual analog scale score of ≥ 2 for LBP. The patients were classified into the LBP-improved or LBP-continued groups based on the visual analog scale for LBP at 1 year after THA. Preoperative and postoperative changes in the coronal and sagittal spinal parameters were compared between the 2 groups after propensity score matching for age, sex, body mass index, and preoperative spinal parameters.

RESULTS

A total of 161 patients (61.7%) were classified into the LBP-improved group. After 85 patients in both groups were matched, the LBP-improved group showed significant differences in spinal parameter changes, which were a higher lumbar lordosis (LL) (P = .04) and lower sagittal vertical axis (SVA) (P = .02) and pelvic incidence (PI) minus LL (PI-LL) (P = .01) postoperatively, whereas the LBP-continued group showed worsened changes in LL and SVA and PI-LL mismatch.

CONCLUSION

Patients who had LBP improvement after THA had significant differences in spinal parameter changes in LL, SVA, and PI-LL. These spinal parameters may be the key factors in the mechanism of LBP improvement after THA.

Chronic disease clusters are associated with prolonged, bothersome, and multisite musculoskeletal pain: a population-based study on Northern Finns

BACKGROUND

Chronic diseases often accumulate with musculoskeletal (MSK) pain. However, less evidence is available on idiosyncratic patterns of chronic diseases and their relationships with the severity of MSK pain in general MSK pain populations.

MATERIAL AND METHODS

Questionnaire-based data on physician-diagnosed chronic diseases, MSK pain and its dimensions (frequency, intensity, bothersomeness, and the number of pain sites), and confounders were collected from the Northern Finland Birth Cohort 1966 at the age of 46. Latent Class Analysis (LCA) was used to identify chronic disease clusters among individuals who reported any MSK pain within the previous year (n = 6105). The associations between chronic disease clusters, pain dimensions, and severe MSK pain, which was defined as prolonged (over 30 d within the preceding year), bothersome (Numerical Rating Scale >5), and multisite (two or more pain sites) pain, were analyzed using logistic regression and general linear regression models, adjusted for sex and educational level (n for the full sample = 4768).

RESULTS

LCA resulted in three clusters: Metabolic (10.8% of the full sample), Psychiatric (2.9%), and Relatively Healthy (86.3%). Compared to the Relatively Healthy cluster, the Metabolic and Psychiatric clusters had higher odds for daily pain and higher mean pain intensity, bothersomeness, and the number of pain sites. Similarly, the odds for severe MSK pain were up to 75% (95% confidence interval: 44%-113%) and 155% (81%-259%) higher in the Metabolic and Psychiatric clusters, respectively, after adjustments for sex and educational level.

CONCLUSIONS

Distinct patterns of chronic disease accumulation can be identified in the general MSK pain population. It seems that mental and metabolic health are at interplay with severe MSK pain. These findings suggest a potential need to screen for psychiatric and metabolic entities of health when treating working-aged people with MSK pain.Key messagesThis large study on middle-aged people with musculoskeletal pain aimed to examine the idiosyncratic patterns of chronic diseases and their relationships with the severity of musculoskeletal pain. Latent class cluster analysis identified three chronic disease clusters: Psychiatric, Metabolic, and Relatively Healthy. People with accumulated mental (Psychiatric cluster) or metabolic diseases (Metabolic cluster) experienced more severe pain than people who were relatively healthy (Relatively Healthy cluster). These findings suggest a potential need to screen for psychiatric and metabolic entities of health when treating working-aged people with MSK pain.

The crosstalk of the pathophysiologic models in fibromyalgia

Fibromyalgia (FM) is a heterogeneous condition with various mechanisms (endotype) and manifestations (phenotypes). Many worthy endeavors have been dedicated to exploring the main trajectories of FM pathogenesis, depicted as the models of FM development. The Imbalance of Threat and Soothing Systems (FITSS) model, which is an advancing psychosocial form of the "central sensitization" model, and autonomic nervous system (ANS) model, besides new discoveries of potential pathways for FM development such as autoimmunity, small fiber pathology, and gut-brain axis currently comprise all our knowledge assets about FM pathogenesis. The pathophysiology of fibromyalgia is too complex to justify with one model, one main loop of pathogenesis, and one terminator. It appears that the variable FM models could justify some phenotypes of FM. Currently, our knowledge about FM pathogenesis and trying to match the different pathways and links mimic solving a puzzle in the hands of beginners. Until unraveling many missed interconnections and formulas between numerous scrambled pieces of the FM puzzle, proposing an integrated model seems not possible. This review focuses on the main trajectories of FM pathogenesis proposed thus far and tries to illuminate the crosstalking between them. We also propose the subgrouping FM into more homogenous categories based on the endotype-phenotype characteristics. It could provide a more pragmatic approach toward understanding of the diverse network of FM pathogenesis as well as the personalized stratification of FM. Key Points • The disentangled nature of FM pathogenesis escapes from embracing under one integrated model. • There appears to be no way for formulizing FM pathogenesis except the acknowledgment of the different pathways and their crosstalk explored as yet. • Acknowledging the different endotypes/phenotypes of FM spectrum and classifying them into more homogenous groups can help to the pragmatic approach to FM.

The Interconnection Between Social Support and Emotional Distress Among Individuals with Chronic Pain: A Narrative Review

Chronic pain is a public health concern affecting over 100 million U.S. adults. Because chronic pain is multifactorial, it requires a biopsychosocial approach to understand how biological, psychological, and social factors contribute to both the development and maintenance of pain. On average, individuals with chronic pain report higher levels of emotional distress compared to pain-free individuals. Research has demonstrated that social support is associated with better pain outcomes and less emotional distress. It has been proposed that social support may improve pain outcomes by reducing the influence of stressors. However, the majority of research exploring the relationships between social support and pain-related outcomes has focused on the direct relationship between these variables, largely overlooking the process by which social support has a positive influence on pain. This narrative review synthesizes research on how chronic pain, emotional distress, and social support are highly interconnected, yet research investigating chronic pain and emotional distress within a social context is limited. We then highlight disparities in chronic pain, such that the burden of chronic pain is unequal between demographic groups. Next, we discuss existing evidence for the use of group-based interventions to address pain-related outcomes. Lastly, we summarize limitations of prior research studies and highlight gaps in the current literature. Overall, longitudinal research comprehensively investigating the distinct nuances in the measurement of social support and how these nuances relate to emotional distress and pain outcomes is needed and may provide insight into the unique needs of individuals or subgroups. Further, demographically diverse randomized controlled trials are needed to identify the process by which group-based interventions improve pain outcomes and whether these interventions are more effective for particular groups in order to personalize treatment approaches and address inequities in pain care.

Pain-Related Stigma and Its Associations With Clinical and Experimental Pain Severity in Youth With Chronic Musculoskeletal Pain Conditions

OBJECTIVE

Many children with chronic musculoskeletal pain conditions experience stigma which can have negative downstream consequences. This study compares ratings of clinical pain (current pain intensity and pain interference), experimental pain (temporal summation, cold water tolerance, and cold pain intensity), and pain-related stigma among three groups of youth with rheumatic conditions. The relations among ratings of pain-related stigma and pain variables were explored.

METHODS

Eighty-eight youth aged 8-17 years with a diagnosis of juvenile idiopathic arthritis (JIA = 32), juvenile fibromyalgia (JFM = 31), or non-specific chronic pain (NSCP = 25) completed measures of clinical pain ratings (average 7-day pain intensity, day of assessment pain (DoA), and pain interference), experimental pain (cold pain tolerance, cold pain intensity, and temporal summation of mechanical pain), and pain-related stigma. Data analysis compared pain-related stigma and pain ratings across the three groups and examined the relations among pain-related stigma and pain ratings.

RESULTS

Youth with JFM reported higher ratings of clinical pain and pain-related stigma than their counterparts with NSCP or JIA. However, there were no differences in experimental pain. Pain-related stigma was associated with greater ratings of pain interference, particularly for those with JIA and NSCP. Pain-related stigma was also associated with greater average daily pain intensity but not DoA.

CONCLUSION

Youth with medically unexplained pain report greater stigma and worse pain than their peers; thus, robust assessment of pain in this population is necessary. Future work should longitudinally explore the impact of pain-related stigma on pain outcomes and treatment responses.

Focus on the impact of social factors and lifestyle on the disease burden of low back pain: findings from the global burden of disease study 2019

BACKGROUND

Low back pain (LBP) is one of the leading causes of disability worldwide. Differences in social backgrounds and lifestyles in various regions and countries may contribute to the discrepancies in the disease burden of LBP.

METHODS

Based on the GBD 2019, we collected and analyzed numbers and age-standardized rates (ASR) of LBP disability-adjusted life years (DALYs). Temporal trends in ASR were also analyzed using estimated annual percentage change (EAPC). The Age-period-cohort (APC) model was used to estimate age, period and cohort trends in DALYs of LBP. An autoregressive integrated moving average (ARIMA) model was used to forecast DALYs of LBP trends from 2020 to 2035.

RESULTS

The DALYs due to LBP increased from 1990 to 2019. The APC model showed that the risk of DALYs for global LBP increased with age and year and that the risk of DALYs was lower in the later-born cohort than in the earlier-born cohort. The main risk factors which GBD estimates were available for DALYs of LBP include smoking, occupational ergonomic factors and high BMI. It is expected that DALYs of LBP will continue to rise until 2035.

CONCLUSION

From 1990 to 2019, the global disease burden of LBP remained high. It is necessary to pay attention to the influence of social factors and lifestyle on LBP. Focusing on the impact of social factors as well as lifestyle on the prognosis of LBP and targeting interventions may further reduce the disease burden of LBP.

Polygenic Contributions to Chronic Overlapping Pain Conditions in a Large Electronic Health Record Sample

Chronic overlapping pain conditions (COPCs) are believed to share common etiological mechanisms involving central sensitization. Genetic and environmental factors putatively combine to influence susceptibility to central sensitization and COPCs. This study employed a genome-wide polygenic risk score approach to evaluate genetic influences on 8 common COPCs. COPCs were identified by International Classification of Disease codes in Vanderbilt's deidentified clinical biorepository (BioVU), with each COPC condition empirically weighted for the level of central sensitization based on prior work. A centralized pain score (CPS) was calculated for 55,340 individuals by summing the weighted number of COPCs. Overall, 12,502 individuals (22.6%) were diagnosed with at least 1 COPC, with females exhibiting nearly twice the mean CPS as males. To assess the genetic influence on centralized pain in COPCs, 6 pain polygenic risk scores (PRSs) were developed using UK Biobank data to predict 6 pain criteria (no pain, neck/shoulder, abdomen, hip, knee, low back pain). These PRSs were then deployed in the BioVU cohort to test for association with CPS. In regression models adjusted for age, sex, and BMI, all pain PRSs except hip pain were significantly associated with CPS. Our findings support a shared polygenic influence across COPCs potentially involving central sensitization mechanisms. PERSPECTIVE: This study used a polygenic risk score approach to investigate genetic influences on chronic overlapping pain conditions. Significant findings in this study provide evidence supporting previous hypotheses that a shared polygenic influence involving central sensitization may underly chronic overlapping pain conditions and can guide future biomarker and risk assessment research.

Preclinical orofacial pain assays and measures and chronic primary orofacial pain research: where we are and where we need to go

Chronic primary orofacial pain (OFP) conditions such as painful temporomandibular disorders (pTMDs; i.e., myofascial pain and arthralgia), idiopathic trigeminal neuralgia (TN), and burning mouth syndrome (BMS) are seemingly idiopathic, but evidence support complex and multifactorial etiology and pathophysiology. Important fragments of this complex array of factors have been identified over the years largely with the help of preclinical studies. However, findings have yet to translate into better pain care for chronic OFP patients. The need to develop preclinical assays that better simulate the etiology, pathophysiology, and clinical symptoms of OFP patients and to assess OFP measures consistent with their clinical symptoms is a challenge that needs to be overcome to support this translation process. In this review, we describe rodent assays and OFP pain measures that can be used in support of chronic primary OFP research, in specific pTMDs, TN, and BMS. We discuss their suitability and limitations considering the current knowledge of the etiology and pathophysiology of these conditions and suggest possible future directions. Our goal is to foster the development of innovative animal models with greater translatability and potential to lead to better care for patients living with chronic primary OFP.

The NLRP3 inflammasome: role in the pathobiology of chronic pain

Chronic pain is not only one of the most common health problems, it is often challenging to treat adequately. Chronic pain has a high prevalence globally, affecting approximately 20% of the adult population. Chronic inflammatory pain and neuropathic (nerve) pain conditions are areas of large unmet medical need because analgesic/adjuvant agents recommended for alleviation of these types of chronic pain often lack efficacy and/or they produce dose-limiting side effects. Recent work has implicated the NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome in the pathobiology of chronic pain, especially neuropathic and inflammatory pain conditions. NLRP3 is activated by damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs). This in turn leads to recruitment and activation of caspase-1 an enzyme that cleaves the inactive IL-1β and IL-18 precursors to their respective mature pro-inflammatory cytokines (IL-1β and IL-18) for release into the cellular milieu. Caspase-1 also cleaves the pyroptosis-inducing factor, gasdermin D, that leads to oligomerization of its N-terminal fragment to form pores in the host cell membrane. This then results in cellular swelling, lysis and release of cytoplasmic contents in an inflammatory form of cell death, termed pyroptosis. The ultimate outcome may lead to the development of neuropathic pain and/or chronic inflammatory pain. In this review, we address a role for NLRP3 inflammasome activation in the pathogenesis of various chronic pain conditions.

The development and measurement properties of the Dutch version of the fear-avoidance components scale (FACS-D) in persons with chronic musculoskeletal pain

OBJECTIVES

The Fear-Avoidance Components Scale (FACS) is a recently developed patient-reported instrument assessing different constructs related to the fear-avoidance model of pain. The aim was to translate the original English FACS into Dutch (FACS-D) and assess its measurement properties in persons with chronic musculoskeletal pain.

METHODS

The original English FACS (20 item-scale, range: 0-100) was translated in Dutch through standard forward-backward translation methodology. The FACS-D's measurement properties were evaluated in 224 persons with chronic musculoskeletal pain. Internal consistency, test-retest reliability and measurement error were assessed with the Cronbach's alpha coefficient (α), intraclass correlation coefficient (ICC), and standard error of measurement (SEM). Construct validity was assessed through inter-item correlation analyses, exploratory factor analysis, association with other fear-avoidance-related constructs, and hypothesis testing.

RESULTS

Internal consistency, test-retest reliability and hypotheses testing were good (α=0.92; ICC=0.92, CI 0.80-0.96; 7/8 hypotheses confirmed). Similar to the original FACS and other translated versions, a two-factor model best fit the data. However, the item distribution differed from other versions. One factor represented "pain-related cognitions and emotions" and a second factor represented "avoidance behaviour." In contrast to the original FACS, low inter-item correlations for item 12 were found. The FACS-D was more strongly associated with fear-avoidance-related constructs of pain severity, perceived disability, feelings of injustice, and depressive/anxiety symptoms than the other fear-avoidance-related scales studied here.

CONCLUSIONS

The FACS-D demonstrated good reliability and construct validity, suggesting that it may be a useful measure for Dutch-speaking healthcare providers. Two clinically relevant factors, with a different item distribution than the original FACS, were identified: one covering items on pain-related cognitions and emotions, and one covering items on avoidance behaviour. The stronger association between FACS-D and fear-avoidance related constructs suggests that the FACS-D may be more effective in evaluating the cognitive, emotional and behavioural constructs of pain-related fear-avoidance than other similar measures.

Do lumbar intervertebral disc parameters in patients with chronic low back pain differ quantitatively from healthy individuals? A comparative study

Objectives: Studies in the past were not able to find any definitive correlation between disc parameters and LBP. The objectives of the current study were to evaluate the association of the lumbar disc parameters with LBP and to find the quantitative differences between the discs in LBP patients and healthy individuals. Methodology: Fifty patients with chronic LBP (group A) and 25 healthy individuals (group B) were subjected to magnetic resonance imaging of lumbar spine. Disc parameters of orientation and size were estimated. Results: There was a statistically significant difference in disc angle at L1-L2 ( p = 0.01), L2-L3 ( p = 0.05), and L3-L4 ( p = 0.001), and skin angle at L2-L3 ( p = 0.03) and L4-L5 ( p = 0.05) level. Length and cross-sectional area (CSA) of anterior intervertebral height, posterior intervertebral height, intervertebral disc, anterior disc material, posterior disc material; and volume of anterior disc material and volume of posterior disc material were statistically significantly more at various disc levels in group A. Antero-posterior dural sac length and CSA of the sac were statistically significantly smaller at L4-L5 and L5-S1 levels. There was a significant association between average disc height and dural sac area at L1-L2 ( p-value = 0.0393) and L5-S1 ( p-value = 0.0022) and CSA of the disc and dural sac area at L5-S1 ( p-value = 0.049) in group A. Conclusions: There was a significant difference in the lumbar disc orientation and dimensions between LBP patients and healthy individuals. Larger disc parameters (height, volume, CSA, and length) and altered orientation may affect the biomechanics of the spine, thus predisposing to LBP.

A Shared Genetic Signature for Common Chronic Pain Conditions and its Impact on Biopsychosocial Traits

The multiple comorbidities & dimensions of chronic pain present a formidable challenge in disentangling its aetiology. Here, we performed genome-wide association studies of 8 chronic pain types using UK Biobank data (N =4,037-79,089 cases; N = 239,125 controls), followed by bivariate linkage disequilibrium-score regression and latent causal variable analyses to determine (respectively) their genetic correlations and genetic causal proportion (GCP) parameters with 1,492 other complex traits. We report evidence of a shared genetic signature across chronic pain types as their genetic correlations and GCP directions were broadly consistent across an array of biopsychosocial traits. Across 5,942 significant genetic correlations, 570 trait pairs could be explained by a causal association (|GCP| >0.6; 5% false discovery rate), including 82 traits affected by pain while 410 contributed to an increased risk of chronic pain (cf. 78 with a decreased risk) such as certain somatic pathologies (eg, musculoskeletal), psychiatric traits (eg, depression), socioeconomic factors (eg, occupation) and medical comorbidities (eg, cardiovascular disease). This data-driven phenome-wide association analysis has demonstrated a novel and efficient strategy for identifying genetically supported risk & protective traits to enhance the design of interventional trials targeting underlying causal factors and accelerate the development of more effective treatments with broader clinical utility. PERSPECTIVE: Through large-scale phenome-wide association analyses of >1,400 biopsychosocial traits, this article provides evidence for a shared genetic signature across 8 common chronic pain types. It lays the foundation for further translational studies focused on identifying causal genetic variants and pathophysiological pathways to develop novel diagnostic & therapeutic technologies and strategies.

Machine Learning Prediction and Phyloanatomic Modeling of Viral Neuroadaptive Signatures in the Macaque Model of HIV-Mediated Neuropathology

In human immunodeficiency virus (HIV) infection, virus replication in and adaptation to the central nervous system (CNS) can result in neurocognitive deficits in approximately 25% of patients with unsuppressed viremia. While no single viral mutation can be agreed upon as distinguishing the neuroadapted population, earlier studies have demonstrated that a machine learning (ML) approach could be applied to identify a collection of mutational signatures within the virus envelope glycoprotein (Gp120) predictive of disease. The S[imian]IV-infected macaque is a widely used animal model of HIV neuropathology, allowing in-depth tissue sampling infeasible for human patients. Yet, translational impact of the ML approach within the context of the macaque model has not been tested, much less the capacity for early prediction in other, noninvasive tissues. We applied the previously described ML approach to prediction of SIV-mediated encephalitis (SIVE) using gp120 sequences obtained from the CNS of animals with and without SIVE with 97% accuracy. The presence of SIVE signatures at earlier time points of infection in non-CNS tissues indicated these signatures cannot be used in a clinical setting; however, combined with protein structural mapping and statistical phylogenetic inference, results revealed common denominators associated with these signatures, including 2-acetamido-2-deoxy-beta-d-glucopyranose structural interactions and high rate of alveolar macrophage (AM) infection. AMs were also determined to be the phyloanatomic source of cranial virus in SIVE animals, but not in animals that did not develop SIVE, implicating a role for these cells in the evolution of the signatures identified as predictive of both HIV and SIV neuropathology. IMPORTANCE HIV-associated neurocognitive disorders remain prevalent among persons living with HIV (PLWH) owing to our limited understanding of the contributing viral mechanisms and ability to predict disease onset. We have expanded on a machine learning method previously used on HIV genetic sequence data to predict neurocognitive impairment in PLWH to the more extensively sampled SIV-infected macaque model in order to (i) determine the translatability of the animal model and (ii) more accurately characterize the predictive capacity of the method. We identified eight amino acid and/or biochemical signatures in the SIV envelope glycoprotein, the most predominant of which demonstrated the potential for aminoglycan interaction characteristic of previously identified HIV signatures. These signatures were not isolated to specific points in time or to the central nervous system, limiting their use as an accurate clinical predictor of neuropathogenesis; however, statistical phylogenetic and signature pattern analyses implicate the lungs as a key player in the emergence of neuroadapted viruses.

A novel computational approach to pain perception modelling within a Bayesian framework using quantitative sensory testing

Pain perception can be studied as an inferential process in which prior information influences the perception of nociceptive input. To date, there are no suitable psychophysical paradigms to measure this at an individual level. We developed a quantitative sensory testing paradigm allowing for quantification of the influence of prior expectations versus current nociceptive input during perception. Using a Pavlovian-learning task, we investigated the influence of prior expectations on the belief about the varying strength of association between a painful electrical cutaneous stimulus and a visual cue in healthy subjects (N = 70). The belief in cue-pain associations was examined with computational modelling using a Hierarchical Gaussian Filter (HGF). Prior weighting estimates in the HGF model were compared with the established measures of conditioned pain modulation (CPM) and temporal summation of pain (TSP) assessed by cuff algometry. Subsequent HGF-modelling and estimation of the influence of prior beliefs on perception showed that 70% of subjects had a higher reliance on nociceptive input during perception of acute pain stimuli, whereas 30% showed a stronger weighting of prior expectations over sensory evidence. There was no association between prior weighting estimates and CPM or TSP. The data demonstrates relevant individual differences in prior weighting and suggests an importance of top-down cognitive processes on pain perception. Our new psychophysical testing paradigm provides a method to identify individuals with traits suggesting greater reliance on prior expectations in pain perception, which may be a risk factor for developing chronic pain and may be differentially responsive to learning-based interventions.

Biopsychosocial influence on shoulder pain: results from a randomized preclinical trial of exercise-induced muscle injury

ABSTRACT

Prior cohort studies validated that a subgroup defined by a specific COMT genotype and pain catastrophizing is at increased risk for heightened responses to exercise-induced or surgically induced shoulder pain. In this clinical trial, we used our preclinical model of exercise-induced muscle injury and pain to test the efficacy of interventions matched to characteristics of this high-risk subgroup (ie, personalized medicine approach). Potential participants provided informed consent to be screened for eligibility based on subgroup membership and then, as appropriate, were enrolled into the trial. Participants (n = 261) were randomized to 1 of 4 intervention groups comprised of pharmaceutical (propranolol or placebo) and informational (general education or psychologic intervention) combinations. After muscle injury was induced, participants received randomly assigned treatment and were followed for the primary outcome of shoulder pain intensity recovery over 4 consecutive days. Recovery rates were 56.4% (placebo and psychologic intervention), 55.4% (placebo and general education), 62.9% (propranolol and psychologic intervention), and 56.1% (propranolol and general education). No statistical differences were found between intervention groups in the primary analyses. Additional analyses found no differences between these intervention groups when shoulder pain duration was an outcome, and no differential treatment responses were detected based on sex, race, or level of pain catastrophizing. This trial indicates that these treatments were not efficacious for this high-risk subgroup when shoulder pain was induced by exercise-induced muscle injury. Accordingly, this phenotype should only be used for prognostic purposes until additional trials are completed in clinical populations.

Rs11726196 Single-Nucleotide Polymorphism of the Transient Receptor Potential Canonical 3 (TRPC3) Gene Is Associated with Chronic Pain

Chronic pain is reportedly associated with the transient receptor potential canonical 3 (TRPC3) gene. The present study examined the genetic associations between the single-nucleotide polymorphisms (SNPs) of the TRPC3 gene and chronic pain. The genomic samples from 194 patients underwent linkage disequilibrium (LD) analyses of 29 SNPs within and around the vicinity of the TRPC3 gene. We examined the associations between the SNPs and the susceptibility to chronic pain by comparing the genotype distribution of 194 patients with 282 control subjects. All SNP genotype data were extracted from our previous whole-genome genotyping results. Twenty-nine SNPs were extracted, and a total of four LD blocks with 15 tag SNPs were observed within and around the TRPC3 gene. We further analyzed the associations between these tag SNPs and chronic pain. The rs11726196 SNP genotype distribution of patients was significantly different from the control subjects even after multiple-testing correction with the number of SNPs. The TT + TG genotype of rs11726196 is often carried by chronic pain patients, suggesting a causal role for the T allele. These results contribute to our understanding of the genetic risk factors for chronic pain.

Pain sensitivity is modulated by affective temperament: Results from the population-based CHRIS Affective Disorder (CHRIS-AD) study

BACKGROUND

Nociceptive pain modulation is related to psychological and psychiatric conditions. Evidence from clinical studies backs innate temperaments as potential precursors of mood symptoms and disorders, and pain sensitivity. Our study examines the modulation effect of affective temperaments on pain sensitivity in a general population adult sample, accounting for possible intervening mood symptoms, lifetime anxiety and depression, and pain treatments.

METHODS

The sample is part of the CHRIS-AD study, Italy. Primary outcomes were the pain sensitivity questionnaire PSQ-total intensity score and the experimental pressure pain threshold (PPT). Affective temperaments were evaluated with the TEMPS-M. Lifetime depression, anxiety, current mood disorders, and treatments were self-reported via rating-scales. Directed acyclic graphs theory guided linear and mixed linear regression model analyses.

RESULTS

Among 3804 participants (aged 18-65; response rate 78.4 %, females 53.3 %, mean age 38.4 years) for any given temperament, both the PSQ-total and the PPT were associated with temperament. The TEMPS-M four cyclothymic-related temperaments aligned on the pain-sensitive pole and the hyperthymic on the pain-resilient pole. The inclusion of current or lifetime mood symptoms, or pain drug use, as possible intervening pathways only partly diluted these associations, with stronger evidence for an effect of trait anxiety.

LIMITATIONS

The main limitations were the lack of experimental measures of suprathreshold pain intensity perception, and detailed information on affective disorders in the study population.

CONCLUSIONS

These findings support the hypothesis of a biological dichotomous diathesis of affective temperaments towards pain sensitivity; hyperthymic suggesting protection, whereas cyclothymic suggesting predisposition.

Effect of Aerobic Exercise on the Levels of Pain, Quality of Life, and Alexithymia in Alexithymic Individuals With Chronic Pain: A Single-Blinded Randomized Controlled Trial

OBJECTIVE

This study aimed to investigate the effects of aerobic exercise on pain, degree of alexithymia, and quality of life in individuals with alexithymia and chronic pain.

METHODS

A total of 40 participants who scored 61 or higher on the Toronto Alexithymia Scale-20 (TAS-20) were included in the study. The sample was subdivided into 2 groups using a computerized randomization program: an aerobic exercise group (n = 20) and a control group (n = 20). Participants in the aerobic exercise group underwent a 30-minute jogging protocol at 60% to 90% of maximum heart rate 3 days per week for 8 weeks under the supervision of a physiotherapist. Participants in the control group continued their daily physical activities. Outcome measures were the TAS-20, visual analog scale, Graded Chronic Pain Scale, and 36-Item Short Form Health Survey.

RESULTS

There was no statistically significant difference between the demographics of the 2 groups (P > .05). There was a statistically significant improvement in TAS-20, Graded Chronic Pain Scale, visual analog scale, and 36-Item Short Form Health Survey scores of the participants in the aerobic exercise group compared to the control group (P ˂ .05).

CONCLUSION

Aerobic exercise had a positive effect on pain, quality of life, and degree of alexithymia in individuals with alexithymia and chronic pain.

Influencing factors of pressure pain hypersensitivity of the upper trapezius in food service workers with nonspecific neck/shoulder myofascial pain: A cross-sectional study

It is unclear which factors contribute to the developing pressure pain hypersensitivity of the upper trapezius, a type of neurophysiological hyperexcitability. The present study investigated the relationship between physical and psychological factors and pressure pain hypersensitivity of the upper trapezius for each sex. In total, 154 individuals with neck/shoulder myofascial pain participated, among 372 food service workers. Participants completed a questionnaire (Beck Depression Inventory, and Borg Rating of Perceived Exertion scale) and were photographed to measure posture. Pressure pain sensitivity, 2 range of motions (cervical lateral bending and rotation), and 4 muscle strengths (serratus anterior, lower trapezius [LT], biceps, and glenohumeral external rotator) were measured by a pressure algometer, iPhone application, and handheld dynamometer, respectively. For each sex, forward multivariate logistic regression was used to test our a priori hypothesis among selected variables that a combination of psychosocial and physical factors contributed to the risk for pressure pain hypersensitivity. In multivariate analyses, LT strength (odds ratio = 0.94, 95% confidence interval = 0.91-0.97, P = .001) was the only significant influencing factor for pressure pain hypersensitivity in men. Dominant painful ipsilateral cervical rotation range of motion (odds ratio = 0.96, 95% confidence interval = 0.92-0.99, P = .037) was the only influencing factor for pressure pain hypersensitivity in women. LT strength and dominant painful ipsilateral cervical rotation range of motion could serve as guidelines for preventing and managing pressure pain hypersensitivity of the upper trapezius in food service workers with nonspecific neck/shoulder myofascial pain.

Depression and work productivity: insights from a longitudinal cohort study on digital care programs for Musculoskeletal conditions

BACKGROUND

Comorbidity between musculoskeletal (MSK) pain and depression is highly common and associated with greater symptom burden and greater loss of work productivity. Multimodal care programs tackling both physical and mental health components may maximize productivity recovery and return to work. Digital delivery of such programs can facilitate access, ensure continuity of care, and enhance patient engagement.

OBJECTIVE

Assess the impact of a completely remote multimodal digital care program (DCP) for MSK pain on mental health and work-related outcomes stratified by baseline depression levels.

METHODS

The present study is an ad-hoc analysis of an interventional, single-arm, cohort study of individuals with MSK pain undergoing a DCP. Three subgroups with different baseline depression severity levels were created based on the Patient Health Questionnaire (PHQ-9): cluster 1 (<5: minimal depression); cluster 2 (5-10: mild depression) and cluster 3 (≥10: moderate depression). The mean change between baseline and end-of-program (8-12 weeks) on depression, anxiety, fear-avoidance beliefs, work productivity and activity impairment and adherence was assessed across subgroups. Outcome changes were analyzed by latent growth curve analysis.

RESULTS

From a total of 7785 eligible participants, 6137 (78.8%) were included in Cluster 1, 1158 (14.9%) in cluster 2 and 490 (6.3%) in cluster 3. Significant improvements in depression and anxiety scores were observed in clusters 2 and 3 but not cluster 1, with average end-of-the program scores in clusters 2 and 3 below the initially defined cluster thresholds (5 and 10 for clusters 2 and 3, respectively). All clusters reported significant improvements in productivity impairment scores (mean changes from -16.82, 95%CI -20.32 to -13.42 in cluster 1 to -20.10, 95%CI -32.64 to -7.57 in cluster 3). Higher adherence was associated with higher improvements in depression in clusters 2 and 3, and with greater recovery in activities of daily living in cluster 3. Overall patient satisfaction was 8.59/10.0 (SD 1.74).

CONCLUSIONS

A multimodal DCP was able to promote improvements in productivity impairment scores comparable to those previously reported in the literature, even in participants with comorbid depression and anxiety. These results reinforce the need to follow a biopsychosocial framework to optimize outcomes in patients with MSK pain.

CLINICALTRIAL

ClinicalTrials.gov NCT04092946; https://clinicaltrials.gov/ct2/show/NCT04092946.

Profiles of Risk and Resilience in Chronic Pain: Loneliness, Social Support, Mindfulness, and Optimism Coming out of the First Pandemic Year

Objective

Individuals experience chronic pain differently, not only because of different clinical diagnoses, but also because of differing degrees of influence from biopsychosocial pain modulators. We aimed to cluster patients with chronic pain into distinct subgroups based on psychosocial characteristics and pain intensity, and we subsequently examined group differences in pain-related interference approximately 1 year later.

Methods

In this observational, longitudinal study, patients with chronic pain (n = 94) completed validated assessments of psychosocial characteristics and pain intensity at the beginning of COVID-19–related social distancing (April to June 2020). One year later (May to June 2021), patients completed a follow-up survey with assessments of pain interference, loneliness, social support, mindfulness, and optimism.

Results

A cluster analysis, using psychosocial factors and pain intensity, empirically produced three patient groups: 1) psychosocial predominant (PSP), characterized by high psychosocial distress and average pain intensity; 2) pain intensity predominant (PIP), characterized by average psychosocial distress and high pain intensity; and 3) less elevated symptoms (LES), characterized by low psychosocial distress and low pain intensity. At the 1-year follow-up, patients in the PSP and PIP clusters suffered greater pain interference than patients in the LES cluster, while patients in the PSP cluster also reported greater loneliness and lower mindfulness and optimism.

Conclusions

An empirical psychosocial-based clustering of patients identified three distinct groups that differed in pain interference. Patients with high psychosocial modulation of pain at the onset of social distancing (the PSP cluster) suffered not only greater pain interference but also greater loneliness and lower levels of mindfulness and optimism, which suggests some potential behavioral targets for this group in the future.

Acute inflammatory response via neutrophil activation protects against the development of chronic pain

The transition from acute to chronic pain is critically important but not well understood. Here, we investigated the pathophysiological mechanisms underlying the transition from acute to chronic low back pain (LBP) and performed transcriptome-wide analysis in peripheral immune cells of 98 participants with acute LBP, followed for 3 months. Transcriptomic changes were compared between patients whose LBP was resolved at 3 months with those whose LBP persisted. We found thousands of dynamic transcriptional changes over 3 months in LBP participants with resolved pain but none in those with persistent pain. Transient neutrophil-driven up-regulation of inflammatory responses was protective against the transition to chronic pain. In mouse pain assays, early treatment with a steroid or nonsteroidal anti-inflammatory drug (NSAID) also led to prolonged pain despite being analgesic in the short term; such a prolongation was not observed with other analgesics. Depletion of neutrophils delayed resolution of pain in mice, whereas peripheral injection of neutrophils themselves, or S100A8/A9 proteins normally released by neutrophils, prevented the development of long-lasting pain induced by an anti-inflammatory drug. Analysis of pain trajectories of human subjects reporting acute back pain in the UK Biobank identified elevated risk of pain persistence for subjects taking NSAIDs. Thus, despite analgesic efficacy at early time points, the management of acute inflammation may be counterproductive for long-term outcomes of LBP sufferers.

The association between chronic pain and pre-and-post migration experiences in resettled humanitarian refugee women residing in Australia

Background

Refugee women are potentially at increased risk for chronic pain due to circumstances both in the pre-migration and post-settlement setting. However, this relationship between refugee-related challenges introduced along their migration trajectories and chronic pain remains unclear. This study will therefore examine the association between pre- and post-migration factors and chronic pain in refugee women five years into resettlement in Australia.

Methods

The first five waves of data from the ‘Building a New Life in Australia’ longitudinal study of humanitarian refugees living in Australia was analysed using logistic regression models to investigate the association between predictor variables and chronic pain. The study outcome was chronic pain and predictors were migration process and resettlement factors in both the pre-and post-settlement setting.

Results

Chronic pain was reported in 45% (n = 139) of women, and among these a further 66% (n = 120) also reported having a long-term disability or health condition that had lasted 12 months. Pre- migration factors such as increasing age (OR 1.08; 95% CI 1.05, 1.11) and women who migrated under the Women at Risk Visa category (OR 2.40; 95% CI 1.26, 4.56) had greater odds of experiencing chronic pain. Interestingly, post migration factors such as women with better general health (OR 0.04; 95% CI 0.01, 0.11) or those who settled within metropolitan cities (OR 0.29; 95% CI 0.13, 0.68) had lower odds of experiencing chronic pain, and those who experience discrimination (OR 11.23; 95% CI 1.76, 71.51) had greater odds of experiencing chronic pain.

Conclusion

Our results show that there is a high prevalence of chronic pain in refugee women across the initial years of resettlement in Australia. This may be in part due to pre-migration factors such as age and migration pathway, but more significantly the post migration context that these women settle into such as rurality of settlement, poorer general health and perceived discriminatory experiences. These findings suggest that there may be many unmet health needs which are compounded by the challenges of resettlement in a new society, highlighting the need for increased clinical awareness to help inform refugee health care and settlement service providers managing chronic pain.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-13226-5.

Tibetan Herbal Pain-Relieving Plaster for Chronic Musculoskeletal Pain Among Cancer Survivors: Study Protocol of a Randomized, Double-Blind, Placebo-Controlled Trial

Chronic pain is common and debilitating in cancer survivors. Tibetan herbal pain-relieving plaster is used as an external analgesic to treat musculoskeletal pain in China; however, its safety and efficacy have not been evaluated via clinical trials in cancer survivors. We designed this Phase II randomized, double-blind, placebo-controlled trial (ClinicalTrials.gov Identifier: NCT04916249) to assess the efficacy and safety of the pain-relieving plaster for temporary pain relief among cancer survivors with chronic musculoskeletal pain. Under ethical approval from the Institutional Review Board at the Memorial Sloan Kettering Cancer Center, we will enroll eligible cancer survivors who have a clinical diagnosis of moderate to severe chronic musculoskeletal pain in this study. We use a central randomization system to allocate the eligible participants to either the treatment or the control group in a 1:1 ratio, with stratification by baseline opioid use. We will instruct the participants to apply the herbal patch (Tibetree Pain-Relieving Plaster, Tibet Cheezheng Tibetan Medicine Co. Ltd., Tibet, China) or placebo patch daily at the focal area with worst pain for 14 consecutive days. Study physician, participant, outcome assessor, and biostatistician are blinded to the group allocation. The primary outcome is pain severity measured by the Brief Pain Inventory on Days 2–7. Secondary outcomes include changes in insomnia, anxiety, depression, fatigue, pressure pain threshold, pain medication use, and global impression of change. We will also monitor the adverse events throughout the study period. Statistical analysis will follow the intention-to-treat principle and linear mixed modeling will be used. With rigorous design and implementation, this randomized, placebo-controlled trial will provide the initial evidence on the efficacy and safety of the pain-relieving plaster for pain relief among cancer survivors with chronic musculoskeletal pain.

Pulp sensibility tests responses in patients with anxiety and depression

Background

In view of the importance of pulp sensibility tests in clinical decision-making and the impact of psychological factors on test results, we evaluated in this study dental pulp responses to pulp sensibility tests (ie, cold and electric) in patients with anxiety and depression.

Material and Methods

A number of 90 people age 20 to 30 participated in the study, including 30 healthy and 60 with anxiety and depression, whose disorder was approved by a psychiatrist based on the Symptom Checklist 90-R questionnaire. Pulp sensibility tests included electric and cold ones were performed on lateral mandibular teeth. The cold test results were recorded based on the visual analogue scale (VAS) pain scoring (0 no response, 10 worst pain). Electric pulp test was performed using a digital pulp tester. The lowest current that stimulated a pulp response was recorded. The data were analyzed using the Mann-Whitney and Kruskal-Wallis tests.

Results

The cold test pain intensity was significantly higher in patients than in healthy subjects and was significantly associated with the severity of anxiety and depression. In addition, the electric pulp test current to evoke a response was significantly lower in patients than in healthy subjects and was also significantly associated with the severity of anxiety and depression.

Conclusions

Given the limitations of this study, anxiety and depression significantly affect the results of pulp sensibility tests. Key words:Anxiety, Cold pulp test, depression, electric pulp testing.

International Publication Trends in Low Back Pain Research: A Bibliometric and Visualization Analysis

Background

Although there is a growing research base on low back pain, the bibliometric literature related to it is deficient. The aim of this study was to conduct a bibliometric and visualization analysis of low back pain and to provide a broad view of the current trends in LBP research and a potential guide in this discipline.

Methods

The authors searched the Web of Science to extract publications regarding low back pain, and found a total of 12,249 publications during a period of 22 years, among which 12,242 were eligible. We classified and analyzed publications such as total citations, average citations per item, H-index, research types, countries/regions, institutions, and journals using standard bibliometric indicators. Bibliometric approaches (VOSviewer1.6.13 and CiteSpace 5.8.3) were also available for gathering information and explore the trends of research.

Results

Conspicuously, over the past 22 years, an increasing number of scholars have specialized in the research of LBP, exerting the boom in articles. The largest number of document type was that of articles. Under modern conditions, regional distinction existed in the research of low back pain and developed countries preceded others. Research individuals and institutions were preoccupied by respective aspects. Visualization analysis provided objective information for potential collaborators and cooperative institutions. Furthermore, most burst keywords varied during different periods.

Conclusions

The map of research on LBP obtained by our analysis is expected to help researchers to efficiently and effectively explore LBP.

Quantitative Sensory Testing Across Chronic Pain Conditions and Use in Special Populations

Chronic pain imposes a significant burden to the healthcare system and adversely affects patients' quality of life. Traditional subjective assessments, however, do not adequately capture the complex phenomenon of pain, which is influenced by a multitude of factors including environmental, developmental, genetic, and psychological. Quantitative sensory testing (QST), established as a protocol to examine thermal and mechanical sensory function, offers insight on potential mechanisms contributing to an individual's experience of pain, by assessing their perceived response to standardized delivery of stimuli. Although the use of QST as a research methodology has been described in the literature in reference to specific pain populations, this manuscript details application of QST across a variety of chronic pain conditions. Specific conditions include lower extremity chronic pain, knee osteoarthritis, chronic low back pain, temporomandibular joint disorder, and irritable bowel syndrome. Furthermore, we describe the use of QST in placebo/nocebo research, and discuss the use of QST in vulnerable populations such as those with dementia. We illustrate how the evaluation of peripheral sensory nerve function holds clinical promise in targeting interventions, and how using QST can enhance patient education regarding prognostic outcomes with particular treatments. Incorporation of QST methodology in research investigations may facilitate the identification of common mechanisms underlying chronic pain conditions, guide the development of non-pharmacological behavioral interventions to reduce pain and pain-related morbidity, and enhance our efforts toward reducing the burden of chronic pain.

Preoperative Factors Associated With Low Back Pain Improvement After Total Hip Arthroplasty in a Japanese Population

BACKGROUND

Spinal disorders and low back pain (LBP) have been associated with worse clinical outcomes of total hip arthroplasty (THA). It is essential to identify spinal factors associated with post-THA LBP improvement. Therefore, we aimed to determine the proportion of patients with improved LBP after THA and to identify the preoperative spinal factors associated with LBP improvement.

METHODS

We included 151 patients who underwent primary THA between December 2015 and December 2019 and had a preoperative visual analog scale score for LBP of ≥2. The patients were classified into the LBP improved or LBP continued group based on a visual analog scale score for LBP at 1 year after THA. Preoperative spinal parameters were compared between the 2 groups.

RESULTS

Ninety-five patients (62.9%) were classified into the LBP improved group. Among the coronal spinal parameters, the Cobb angle was significantly lower in the LBP improved group. Among the sagittal spinal parameters, the LBP continued group showed a significantly more posteriorly titled pelvis, lower lumbar lordosis, greater sagittal vertical axis, and greater pelvic incidence minus lumbar lordosis mismatch, indicating a sagittal spinal imbalance. Logistic regression analysis found that preoperative factors associated with LBP improvement after THA had a low Cobb angle and high anterior pelvic plane angle (anteriorly tilted pelvis).

CONCLUSION

Among patients with LBP before THA, 62.9% had improved LBP. Sagittal spinal imbalance and high Cobb angle were the key spinal factors associated with persistent LBP. Our findings suggest that hip surgeons should evaluate spinal alignment before THA in patients with LBP.

An Observational Study Comparing Fibromyalgia and Chronic Low Back Pain in Somatosensory Sensitivity, Motor Function and Balance

Fibromyalgia (FM) and chronic low back pain (CLBP) have shared pathophysiology and have a considerable impact on patients' daily activities and quality of life. The main objective of this study was to compare pain impact, somatosensory sensitivity, motor functionality, and balance among 60 patients with FM, 60 patients with CLBP, and 60 pain-free controls aged between 30 and 65 years. It is essential to know the possible differences existing in symptomatology of two of the major chronic pain processes that most affect the population, such as FM and CLBP. The fact of establishing possible differences in sensory thresholds, motor function, and proprioceptive measures among patients with FM and CLBP could bring us closer to a greater knowledge of the chronic pain process. Through an observational study, a comparison was made between the three groups (FM, CLBP, and pain-free controls) evaluating functional performance, postural balance, kinematic gait parameters, strength, depression, fatigue, and sensitivity to pain and vibration. Patients with chronic pain showed worse somatosensory sensitivity (p < 0.001) and motor function (p < 0.001) than pain-free controls. Moreover, patients with FM showed greater pain impact (p < 0.001) and bigger somatosensory (p < 0.001) and motor deficiencies (p < 0.001) than patients with CLBP. Further research should explore the possible reasons for the greater deterioration in patients with FM in comparison with other chronic pain conditions. Our results, showing the multiple areas susceptible of deterioration, make it necessary to adopt interdisciplinary interventions focused both on physical and emotional dysfunction.

Resting-state functional connectivity patterns are associated with worst pain duration in community-dwelling older adults

INTRODUCTION

An individual's chronic pain history is associated with brain morphometric alterations; but little is known about the association between pain history and brain function.

OBJECTIVES

This cross-sectional study aimed at determining how worst musculoskeletal pain intensity (WPINT) moderated the association between worst musculoskeletal pain duration (WPDUR) and brain resting-state magnetic resonance imaging functional connectivity (RSFC) in community-dwelling older adults (60-94 years, 75% females, 97% right-handed).

METHODS

Resting-state magnetic resonance imaging functional connectivity between region of interests was linearly regressed on WPDUR and WPINT. Predictions were compared with a control group's average RSFC (61-85 years, 47% females, 95% right-handed).

RESULTS

Three significant patterns emerged: (1) the positive association between WPDUR and RSFC between the medial prefrontal cortex, in the anterior salience network (SN), and bilateral lateral Brodmann area 6, in the visuospatial network (VSN), in participants with more severe chronic pain, resulting in abnormally lower RSFC for shorter WPDUR; (2) the negative association between WPDUR and RSFC between right VSN occipitotemporal cortex (lateral BA37 and visual V5) and bilateral VSN lateral Brodmann area 6, independently of WPINT, resulting in abnormally higher and lower RSFC for shorter and longer WPDUR, respectively; and (3) the positive association between WPDUR and the left hemisphere's salience network-default mode network connectivity (between the hippocampus and both dorsal insula and ventral or opercular BA44), independently of WPINT, resulting in abnormally higher RSFC for longer WPDUR.

CONCLUSION

Musculoskeletal effects on brain functional networks of general healthy individuals could accumulate until being observable at older ages. Results invite to examinations of these effects' impact on function and memory.

The plasma microRNA levels and their relationship with the general health and functional status in female patients with fibromyalgia syndrome

Objectives: The aim of this study was to identify the plasma level of micro-ribonucleic acid (microRNA) expressions and the relationship between plasma microRNA levels with the general health and functional status in female patients with fibromyalgia syndrome (FMS).

Patients and methods: Thirty-five female patients (mean age: 42.0±11.8 years; range, 21 to 62 years) diagnosed as FMS and 35 sex-and age-matched healthy controls (mean age: 43.7±8.8 years; range, 21 to 56 years) were enrolled in the study. MicroRNA measurements of the participants in plasma were carried out by using the quantitative polymerase chain reaction (qPCR). A total of 11 plasma levels of microRNA expressions were examined in both groups. The general health and functional status of the patients and controls were assessed by the Fibromyalgia Impact Questionnaire (FIQ) and the Short Form-36 (SF-36) scale.

Results: No significant difference was observed between the plasma levels of microRNA expressions in patients with FMS and healthy controls. The plasma level of miR-320a expression was found to be negatively correlated with the total FIQ score in female patients with FMS (p=0.05, r=-0.34). Negative correlations were also detected between the plasma level of miR-320a and miR-320b expressions and the subscale score of SF-36 physical function in female patients with FMS (p=0.01, r=-0.43 and p=0.01, r=-0.43, respectively). A strong positive correlation was found between miR-142-3p and the subscale score of SF-36 mental symptom score in female patients with FMS (p<0.001, r=1.00).

Conclusion: The expression levels of microRNAs in plasma between female patients with FMS and controls were not significantly different. Only plasma levels of miR-320a, miR-320b, and miR-142-3p expressions were associated with the general health, functional status, and mental symptom score in female patients with FMS.

Juvenile Fibromyalgia

Juvenile fibromyalgia is a common referral in pediatric rheumatology settings. Providing a clear diagnosis and explanation of altered pain processing offers reassurance that pain has a biologic basis and the symptoms are part of a recognized pain syndrome. Physicians should acknowledge the impact of chronic pain and associated symptoms on patient's lives and take time to understand contributing factors including stress, mood, inactivity, and lifestyle factors. The optimal treatment for juvenile fibromyalgia is multidisciplinary, focusing on education about juvenile fibromyalgia, along with physical therapy, cognitive behavioral therapy, sleep hygiene, healthy lifestyle habits, and medications for symptom management as appropriate.

Implications on hypnotherapy: Neuroplasticity, epigenetics and pain

We provide a brief review about the significance of hypnosis with respect to applications and physiological processes in hypnotherapy. Our review concludes that hypnosis is a promising method to manage acute and chronic pain. In addition, we discuss indications pointing toward the view that hypnosis can induce changes in neuroplasticity possibly involving epigenetic mechanisms.

Widespread bodily pain is not associated with the presence of painful TMJ osteoarthritis: a case control study

Purpose: Temporomandibular Joint Arthralgia (TMJA) in the absence of osteoarthritis has not been thoroughly studied. We aimed to investigate the presence of comorbid bodily pain conditions (CBPC) in patients with TMJA with and without TMJOA and hypothesized that TMJOA is not associated with a higher presence of CBPC. Methods: This is a retrospective study involving patients at the University of North Carolina Orofacial Pain Clinic between 2010 and 2014 with TMJA according to the RDC/TMD criteria [1]. Cases fulfilled the Ahmad classification for TMJOA [2], and had TMJA (TMJA+OA), while controls had TMJA only (TMJA-OA). Data was collected from reports of Cone-Beam Computerized Tomography (CBCT). CBPC were self-reported. Results: Twenty-eight cases (TMJA+OA) and 25 controls (TMJA-OA) were included. The mean age of cases and controls (P = 0.027) and mean pain duration differed (P = 0.031). However, the gender distribution (P = 0.552), mean pain intensity (P = 0.381), mean number of painful muscles upon palpation (P = 0.759) and mean number of CBPC (P = 0.575) were not different. At least one CBPC was reported by 68% cases and 72% control subjects (P = 0.743). Conclusions: In this group of patients with TMJA, the presence of CBPC was high and not associated with the presence of TMJOA. This finding suggests that CBPC and TMJOA occur independently.

Chronic Orofacial Pain: Models, Mechanisms, and Genetic and Related Environmental Influences

Chronic orofacial pain conditions can be particularly difficult to diagnose and treat because of their complexity and limited understanding of the mechanisms underlying their aetiology and pathogenesis. Furthermore, there is considerable variability between individuals in their susceptibility to risk factors predisposing them to the development and maintenance of chronic pain as well as in their expression of chronic pain features such as allodynia, hyperalgesia and extraterritorial sensory spread. The variability suggests that genetic as well as environmental factors may contribute to the development and maintenance of chronic orofacial pain. This article reviews these features of chronic orofacial pain, and outlines findings from studies in animal models of the behavioural characteristics and underlying mechanisms related to the development and maintenance of chronic orofacial pain and trigeminal neuropathic pain in particular. The review also considers the role of environmental and especially genetic factors in these models, focussing on findings of differences between animal strains in the features and underlying mechanisms of chronic pain. These findings are not only relevant to understanding underlying mechanisms and the variability between patients in the development, expression and maintenance of chronic orofacial pain, but also underscore the importance for considering the strain of the animal to model and explore chronic orofacial pain processes.

Polygenic risk scoring to assess genetic overlap and protective factors influencing posttraumatic stress, depression, and chronic pain after motor vehicle collision trauma

Posttraumatic stress (PTS), depressive symptoms (DS), and musculoskeletal pain (MSP) are common sequelae of trauma exposure. Although these adverse posttraumatic neuropsychiatric sequelae (APNS) are often studied separately, clinical comorbidity is high. In a cohort of European American motor vehicle collision (MVC) trauma survivors (n = 781), substantial PTS (≥33, IES-R), DS (≥26, CES-D), and MSP (≥4, 0-10 NRS) were identified via a 6-month survey. Genetic risk was estimated using polygenic risk scores (PRSs) calculated from the largest available GWAS datasets of PTSD, MDD, and back pain. We then assessed comorbidity and genetic risk influence for developing chronic PTS, DS, and MSP after MVC. Secondary analyses explored whether common social determinants of health ameliorate genetic vulnerability. We found that 6 months after MVC, nearly half 357/781 (46%) of the participants had substantial PTS, DS, and/or MSP, and overlap was common (PTS + MSP (23%), DS + MSP (18%), PTS + DS (12%)). Genetic risk predicted post-MVC outcomes. PTSD-PRSs predicted PTS and DS (R² = 2.21% and 2.77%, p_adj < 0.01), MDD-PRSs predicted DS and MSP (R² = 1.89%, p_adj < 0.01) and 0.79%, p_adj < 0.05), and back pain-PRS predicted MSP (R² = 1.49%, p_adj < 0.01). Individuals in the highest quintile of PTSD-PRSs had 2.8 and 3.5 times the odds of developing PTS and DS vs. the lowest quintile (95% CI = 1.39-5.75 and 1.58-7.76). Among these high-risk individuals, those living in non-disadvantaged neighborhoods and with college education had 47% (p = 0.048) and 52% (p = 0.04) less risk of developing PTS, and those with high social support had 60% (p = 0.008) less risk of developing DS. Overall, genetic factors influence the risk of APNS after MVC, genetic risk of distinct APNS are overlapping, and specific social determinants greatly augment genetic risk of APNS development after MVC.

Brain Gene Expression Pattern Correlated with the Differential Brain Activation by Pain and Touch in Humans

Genes involved in pain and touch sensations have been studied extensively, but very few studies have tried to link them with neural activities in the brain. Here, we aimed to identify genes preferentially correlated to painful activation patterns by linking the spatial patterns of gene expression of Allen Human Brain Atlas with the pain-elicited neural responses in the human brain, with a parallel, control analysis for identification of genes preferentially correlated to tactile activation patterns. We identified 1828 genes whose expression patterns preferentially correlated to painful activation patterns and 411 genes whose expression patterns preferentially correlated to tactile activation pattern at the cortical level. In contrast to the enrichment for astrocyte and inhibitory synaptic transmission of genes preferentially correlated to tactile activation, the genes preferentially correlated to painful activation were mainly enriched for neuron and opioid- and addiction-related pathways and showed significant overlap with pain-related genes identified in previous studies. These findings not only provide important evidence for the differential genetic architectures of specific brain activation patterns elicited by painful and tactile stimuli but also validate a new approach to studying pain- and touch-related genes more directly from the perspective of neural responses in the human brain.

Bimodal transcranial direct current stimulation reduces alcohol consumption and induces long-term neurochemical changes in rats with neuropathic pain

This study aimed to evaluate the effects of repeated bimodal transcranial direct current stimulation (tDCS) on alcohol consumption and immunohistological and neurochemical parameters in nerve-injured rats. Forty-eight adult male Wistar rats were distributed into six groups: control, neuropathic pain (NP) + sham-tDCS, NP + alcohol + sham-tDCS, alcohol + sham-tDCS, alcohol + tDCS, and NP + alcohol + tDCS. NP is induced by chronic sciatic nerve constriction (CCI). The rats were exposed to a 10% alcohol solution by voluntary consumption for 14 days. From the 16th day after surgery, bimodal tDCS was applied for 20 min/day for 8 days. Brain structures were collected to evaluate the number of neuropeptide Y (NPY)-positive neurons, neurites, and argyrophilic grains by immunohistochemistry, and brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), interleukin (IL)-6, and IL-10 by ELISA. Nerve-injured rats showed a progressive increase in alcohol consumption compared to the non-injured rats. In addition, there was a reduction in voluntary alcohol consumption over time induced by tDCS. Alcohol exposure, chronic pain, and tDCS treatment modulated the central NPY immunoreactivity. tDCS increased the cerebellar levels of IL-6 and IL-10, and CCI and/or tDCS reduced striatal BDNF levels. The current data suggest that tDCS could be a promising non-pharmacological adjuvant to treat patients with chronic pain who use alcohol to relieve their symptoms.

Sensory and Psychological Factors Predict Exercise-Induced Shoulder Injury Responses in a High-Risk Phenotype Cohort

Our prior studies identified a high-risk phenotype (ie, high pain sensitivity variant of the catechol-O-methyltransferase gene (Single Nucleotide Polymorphism [SNP] rs6269) and pain catastrophizing scores) for shoulder pain. The current study identified sensory and psychological predictors of heightened pain responses following exercise-induced shoulder injury. Healthy participants (N = 131) with the SNP rs6269 catechol-O-methyltransferase gene and Pain Catastrophizing Scale scores ≥5 underwent baseline sensory and psychological testing followed by an established shoulder fatigue protocol, to induce muscle injury. Movement-evoked pain, pain intensity, disability, and strength were assessed 24 hours postinjury. Demographic, sensory, and psychological variables were included as predictors in full and parsimonious models for each outcome. The highest variance explained was for the shoulder disability outcome (full model R2 = .20, parsimonious R2 = .13). In parsimonious models, the individual predictors identified were: 1) 1st pulse heat pain sensitivity for isometric shoulder movement-evoked pain and pain intensity; 2) pressure pain threshold for shoulder disability; 3) fear of pain for active shoulder movement-evoked pain and shoulder disability; and 4) depressive symptoms for shoulder strength. Findings indicate specific pain sensitivity and psychological measures may have additional prognostic value for self-reported disability within a high-risk phenotype. These findings should be tested in a clinical cohort for validation. PERSPECTIVE: The current study extends previous work by providing insight regarding how poor shoulder outcomes may develop within a high-risk phenotype. Specifically, 1st pulse heat pain sensitivity and pressure pain threshold were sensory measures, and fear of pain and depressive symptoms were psychological measures, that improved prediction of different shoulder outcomes.