Pain reflects the informational value of nociceptive inputs.

ABSTRACT: Pain perception and its modulation are fundamental to human learning and adaptive behavior. This study investigated the hypothesis that pain perception is tied to pain's learning function. Thirty-one participants performed a threat conditioning task where certain cues were associated with a possibility of receiving a painful electric shock. The cues that signaled potential pain or safety were regularly changed, requiring participants to continually establish new associations. Using computational models, we quantified participants' pain expectations and prediction errors throughout the task and assessed their relationship with pain perception and electrophysiological responses. Our findings suggest that subjective pain perception increases with prediction error, that is, when pain was unexpected. Prediction errors were also related to physiological nociceptive responses, including the amplitude of nociceptive flexion reflex and electroencephalography markers of cortical nociceptive processing (N1-P2-evoked potential and gamma-band power). In addition, higher pain expectations were related to increased late event-related potential responses and alpha/beta decreases in amplitude during cue presentation. These results further strengthen the idea of a crucial link between pain and learning and suggest that understanding the influence of learning mechanisms in pain modulation could help us understand when and why pain perception is modulated in health and disease.

Make me more comfortable: effects of a hypnosis session on pain perception in chronic pain patients.

Introduction: Approximately one-quarter of Canadians experience chronic pain, a debilitating condition often necessitating opioid use, which raises concerns regarding dependency and overdose risks. As an alternative, we developed the HYlaDO program (Hypnose de la Douleur, hypnosis of Pain in French), a novel self-hypnosis approach for chronic pain management. The development of this program followed the ORBIT model, a comprehensive framework for designing interventions encompassing several phases ranging from design to efficacy assessment. Methods: In the present work, we conducted a preliminary evaluation of the HYlaDO program with 21 participants (18 of the 21 patients were included in the analysis). The primary objective was to determine one session of the program's effectiveness in altering pain, anxiety and relaxation via pre-post analysis. The secondary goal was to examine the long-term effects across the same measures, in addition to the overall quality of life. Results: The results highlight the benefits of our approach, while participants reported short-term significant pain reduction, decreased anxiety, and increased relaxation. Additionally, preliminary trends suggest improvements in physical activity and quality of life metrics. Discussion: These positive outcomes highlight HYlaDO's potential as an alternative to opioid therapy for chronic pain. Encouraged by these results, we aim to extend our research to a broader and more diverse cohort, paving the way for comprehensive randomized controlled trials. This expansion will further validate HYlaDO's efficacy and its role in transforming chronic pain management.

Investigating the Impact of Stress on Pain: A Scoping Review on Sense of Control, Social-Evaluative Threat, Unpredictability, and Novelty (STUN Model).

Background: Stress can have paradoxical effects on pain, namely hyperalgesia and hypoalgesia. Four situational characteristics activate the hypothalamic-pituitary-adrenal axis, leading to a physiological stress response: lacking Sense of control, social-evaluative Threat, Unpredictability and Novelty (STUN). This scoping review reports on the types of evidence published on the effects of STUN characteristics on pain outcomes. Databases/Data Treatment: Searches of primary electronic databases were performed to identify articles published on adults between 1990 and 2021 that contained search terms on pain and stress/STUN characteristics. A total of 329 articles were included in the analysis. Results: Only 3.3% of studies examined simultaneously >1 STUN component. Almost all observational studies (177/180) examined the association between perceived stress and pain without measuring physiological stress responses. Of the 130 experimental studies, 78 (60.0%) manipulated stressful characteristics through nociception, and only 38.5% assessed if/how stress manipulation impacted perceived stress. Conclusion: There is a clear lack of integration of the characteristics that trigger a physiological stress response in the pain field. Only 3.3% of studies examined simultaneously more than one STUN component and there is an unequal attention given to individual components of the STUN framework. Recommendations for future research include selection of stress manipulations/measurements that are more precisely inducing/reflecting neurobiological mechanisms of stress responses to insure valid integration of scientific knowledge.

Practicing self-hypnosis to reduce chronic pain: A qualitative exploratory study of HYlaDO.

Background: Nearly a quarter of Canada's population suffers from chronic pain, a long-lasting medical condition marked by physical pain and psychological suffering. Opioids are the primary treatment for pain management in this condition; yet, this approach involves several undesirable side effects. In contrast to this established approach, non-pharmacological interventions, such as medical hypnosis, represent an efficient alternative for pain management in the context of chronic pain. HYlaDO is a self-hypnosis program designed to improve pain management for people with chronic pain. Purpose: This research aimed to evaluate the HYlaDO program based on the proof-of-concept level of the ORBIT model and investigated participants' subjective experience. Research design: Qualitative study. Study sample: Seventeen participants with chronic pain took part in this study. Data collection: We conducted individual semi-structured interviews with patients who had participated in HYlaDO to identify the three targets of desired change: pain, anxiety and autonomy in self-hypnosis practice. Results: Thematic analysis revealed that the practice of hetero-hypnosis and self-hypnosis decreased (i) pain and (ii) anxiety. Also, it (iii) indicated the development of an independent and beneficial self-hypnosis practice by having integrated the techniques taught. Conclusion: These results confirm that the established targets were reached and support further development, implementation and scaling up of this program. Consequently, we believe it is justified to move to the next step of program development.

Facial expression is a distinctive behavioural marker of pain processing in the brain.

Pain is a private experience observable through various verbal and non-verbal behavioural manifestations. Despite the importance of understanding the cerebral mechanisms underlying those manifestations, there is currently limited knowledge on the neural correlates of facial expression of pain. Here, we applied a brain decoding approach to functional magnetic resonance imaging (fMRI) data to predict the facial expression of pain during noxious heat stimulation in healthy volunteers. Results revealed the inability of previously developed pain neurosignatures to predict the facial expression of pain. We thus propose a Facial Expression of Pain Signature (FEPS) conveying distinctive information about the brain response to nociceptive stimulations with minimal overlap with other pain-relevant brain signatures. The FEPS provides a better characterization of the distributed cerebral representations of non-verbal pain communication. This underscores the complexity of pain phenomenology by reinforcing the view that neurosignatures conceived as biomarkers must be interpreted in relation to the specific pain manifestation predicted.

Brain mechanisms associated with facial encoding of affective states.

Affective states are typically accompanied by facial expressions, but these behavioral manifestations are highly variable. Even highly arousing and negative valent experiences, such as pain, show great instability in facial affect encoding. The present study investigated which neural mechanisms are associated with variations in facial affect encoding by focusing on facial encoding of sustained pain experiences. Facial expressions, pain ratings, and brain activity (BOLD-fMRI) during tonic heat pain were recorded in 27 healthy participants. We analyzed facial expressions by using the Facial Action Coding System (FACS) and examined brain activations during epochs of painful stimulation that were accompanied by facial expressions of pain. Epochs of facial expressions of pain were coupled with activity increase in motor areas (M1, premotor and SMA) as well as in areas involved in nociceptive processing, including primary and secondary somatosensory cortex, posterior and anterior insula, and the anterior part of the mid-cingulate cortex. In contrast, prefrontal structures (ventrolateral and medial prefrontal) were less activated during incidences of facial expressions, consistent with a role in down-regulating facial displays. These results indicate that incidences of facial encoding of pain reflect activity within nociceptive pathways interacting or possibly competing with prefrontal inhibitory systems that gate the level of expressiveness.

The Canadian version of the National Institutes of Health minimum dataset for chronic low back pain research: reference values from the Quebec Low Back Pain Study.

ABSTRACT: The National Institutes of Health (NIH) minimum dataset for chronic low back pain (CLBP) was developed in response to the challenge of standardizing measurements across studies. Although reference values are critical in research on CLBP to identify individuals and communities at risk of poor outcomes such as disability, no reference values have been published for the Quebec (Canada) context. This study was aimed to (1) provide reference values for the Canadian version of the NIH minimum dataset among individuals with CLBP in Quebec, both overall and stratified by gender, age, and pain impact stratification (PIS) subgroups, and (2) assess the internal consistency of the minimum data set domains (pain interference, physical function, emotional distress or depression, sleep disturbance, and PIS score). We included 2847 individuals living with CLBP who completed the baseline web survey of the Quebec Low Back Pain Study (age: 44.0 ± 11.2 years, 48.1% women) and were recruited through social media and healthcare settings. The mean score was 6.1 ± 1.8 for pain intensity. Pain interference, physical function, emotional distress or depression, sleep disturbance, and PIS scores were 12.9 ± 4.1, 14.4 ± 3.9, 9.8 ± 4.4, 13.0 ± 3.6, and 26.4 ± 6.6, respectively. Emotional distress or depression showed floor effects. Good-to-excellent internal consistency was found overall and by language, gender, and age subgroups for all domains (alpha: 0.81-0.93) and poor-to-excellent internal consistency for PIS subgroups (alpha: 0.59-0.91). This study presents reference values and recommendations for using the Canadian version of the NIH minimum dataset for CLBP that can be useful for researchers and clinicians.

Trajectories of psychological distress during the COVID-19 pandemic among community-dwelling older adults in Quebec: A longitudinal study.

OBJECTIVE: The COVID-19 pandemic and its associated public health measures may increase the risk for psychological distress among vulnerable older adults. This longitudinal study aimed to identify predictors of psychological distress trajectories among community-dwelling older adults in Quebec, Canada. METHODS: The study spanned four time points across 13 months and three waves of the COVID-19 pandemic. The sample included 645 community-dwelling older adults ages 60 years and older in Quebec. Participants completed telephone-based interviews that included the Kessler 6-item Psychological Distress Scale (K6) to assess psychological distress at each time point as well as information on socioeconomic, medical, psychological and COVID-19 related factors. Group-based trajectory modelling was used to identify distinct trajectories of psychological distress across time. RESULTS: Three group-based trajectories of psychological distress were identified: the resilient (50.5%), reactive (34.9%), and elevated distress groups (14.6%). Individuals with mobility issues, insomnia symptoms, COVID-19 related acute stress, general health anxiety, increased loneliness symptoms, and those unable to use technology to see others were more likely to be in the reactive and elevated groups than the resilient group. Those with past mental health problems had uniquely increased odds of being in the reactive group compared to the resilient group. Individuals living in poverty and those who reported taking psychotropic medication had increased odds of being in the elevated distress group compared to the resilient group. CONCLUSION: These findings characterized distinct trajectories of psychological distress in older adults and identified risk factors for elevated distress levels.

Pharmacological Blockade of Muscle Afferents and Perception of Effort: A Systematic Review with Meta-analysis.

BACKGROUND: The perception of effort provides information on task difficulty and influences physical exercise regulation and human behavior. This perception differs from other-exercise related perceptions such as pain. There is no consensus on the role of group III/IV muscle afferents as a signal processed by the brain to generate the perception of effort. OBJECTIVE: The aim of this meta-analysis was to investigate the effect of pharmacologically blocking muscle afferents on the perception of effort. METHODS: Six databases were searched to identify studies measuring the ratings of perceived effort during physical exercise, with and without pharmacological blockade of muscle afferents. Articles were coded based on the operational measurement used to distinguish studies in which perception of effort was assessed specifically (effort dissociated) or as a composite experience including other exercise-related perceptions (effort not dissociated). Articles that did not provide enough information for coding were assigned to the unclear group. RESULTS: The effort dissociated group (n = 6) demonstrated a slight increase in ratings of perceived effort with reduced muscle afferent feedback (standard mean change raw, 0.39; 95% confidence interval 0.13-0.64). The group effort not dissociated (n = 2) did not reveal conclusive results (standard mean change raw, - 0.29; 95% confidence interval - 2.39 to 1.8). The group unclear (n = 8) revealed a slight ratings of perceived effort decrease with reduced muscle afferent feedback (standard mean change raw, - 0.27; 95% confidence interval - 0.50 to - 0.04). CONCLUSIONS: The heterogeneity in results between groups reveals that the inclusion of perceptions other than effort in its rating influences the ratings of perceived effort reported by the participants. The absence of decreased ratings of perceived effort in the effort dissociated group suggests that muscle afferent feedback is not a sensory signal for the perception of effort.

Brain responses to the vicarious facilitation of pain by facial expressions of pain and fear.

Observing pain in others facilitates self-pain in the observer. Vicarious pain facilitation mechanisms are poorly understood. We scanned 21 subjects while they observed pain, fear and neutral dynamic facial expressions. In 33% of the trials, a noxious electrical stimulus was delivered. The nociceptive flexion reflex (NFR) and pain ratings were recorded. Both pain and fear expressions increased self-pain ratings (fear > pain) and the NFR amplitude. Enhanced response to self-pain following pain and fear observation involves brain regions including the insula (INS) (pain > fear in anterior part), amygdala, mid-cingulate cortex (MCC), paracentral lobule, precuneus, supplementary motor area and pre-central gyrus. These results are consistent with the motivational priming account where vicarious pain facilitation involves a global enhancement of pain-related responses by negatively valenced stimuli. However, a psychophysiological interaction analysis centered on the left INS revealed increased functional connectivity with the aMCC in response to the painful stimulus following pain observation compared to fear. The opposite connectivity pattern (fear > pain) was observed in the fusiform gyrus, cerebellum (I-IV), lingual gyrus and thalamus, suggesting that pain and fear expressions influence pain-evoked brain responses differentially. Distinctive connectivity patterns demonstrate a stronger effect of pain observation in the cingulo-insular network, which may reflect partly overlapping networks underlying the representation of pain in self and others.

Development of a Mixed Hypnosis and Music Intervention Program for the Management of Pain, Anxiety, and Wellbeing in End-of-Life Palliative Care.

Background: The palliative care people present needs that can be partially met by complementary intervention. Approaches based on the use of hypnosis and music are increasingly being studied and have shown potential benefits on pain, anxiety, and wellbeing for many populations including those in palliative care. Objective: This study aims to present the initial process of creating and refining a hypnosis and music intervention program intended for persons in palliative care, with a panel of experts of diverse relevant backgrounds. It also aims to evaluate its feasibility, preliminary acceptability, and content. Methods: To achieve the objectives, we followed ORBIT recommendations for the development and redesign of behavioral interventions (phase I a-b). Based on a meta-analysis, reference interventions were identified and then adapted to the target population. Twenty-two experts from different backgrounds were consulted to obtain their evaluation on the acceptability, feasibility, and content of the interventions. Result: The various components of the program were deemed appropriate or very appropriate by over 80% of the experts. However, possible risks were raised related to some uncertainty about the reactions of individuals to the intervention. Several experts (32%) indicated potential adverse effects consisting of negative emotional experiences during the sessions. Modifications were proposed specifically to reduce or mitigate this risk. Over 90% of the experts considered that the revised program provides a safer and more appropriate intervention for palliative care persons. Conclusion: A mixed intervention program with hypnosis and music has been developed and attained a high level of consensus by the experts. The proposed intervention is ready to be assessed for clinical efficacy in a pilot study (ORBIT Phase II).

Pain Perception in Contact Sport Athletes: A Scoping Review.

Contact sports athletes are regularly facing acute physical pain in part of their sport; however, the literature investigating pain perception in these athletes remains scarce. This scoping review aimed to explore the literature surrounding pain perception in contact sport athletes and to compile and understand how it is studied. The search strategy consisted of using index terms and keywords in the MEDLINE, EMBASE, SPORTDiscus, Web of Science, PsycINFO, CINAHL and ProQuest Dissertations & Theses Global search engines. Results from 11 studies revealed that a mix of team contact sports and combat sports are studied and are included under the umbrella of contact sports. These athletes are being compared with non-athletes as well as athletes from non-contact sports. The cold pressor test and the pain pressure test are the two predominant methods used to investigate physical pain. This review highlights the need to clearly define sports based on contact levels expected in play to better define the types of pain athletes are facing in their practice. Athletes' level of play as well as years of experience should also be more rigorously reported. While contact sport athletes seem to have a higher level of pain tolerance than both active controls and non-contact athletes, the methods of pain testing are not always justified and appropriate in relation to the pain induced during contact sports. Future experimental studies should use pain testing methods relevant to the pain experienced during contact sports and to better justify the rationale for the choice of these methods.

The neural signature of the decision value of future pain.

Pain is a primary driver of action. We often must voluntarily accept pain to gain rewards. Conversely, we may sometimes forego potential rewards to avoid associated pain. In this study, we investigated how the brain represents the decision value of future pain. Participants (n = 57) performed an economic decision task, choosing to accept or reject offers combining various amounts of pain and money presented visually. Functional MRI (fMRI) was used to measure brain activity throughout the decision-making process. Using multivariate pattern analyses, we identified a distributed neural representation predicting the intensity of the potential future pain in each decision and participants' decisions to accept or avoid pain. This neural representation of the decision value of future pain included negative weights located in areas related to the valuation of rewards and positive weights in regions associated with saliency, negative affect, executive control, and goal-directed action. We further compared this representation to future monetary rewards, physical pain, and aversive pictures and found that the representation of future pain overlaps with that of aversive pictures but is distinct from experienced pain. Altogether, the findings of this study provide insights on the valuation processes of future pain and have broad potential implications for our understanding of disorders characterized by difficulties in balancing potential threats and rewards.

Hypnosis and music interventions for anxiety, pain, sleep and well-being in palliative care: systematic review and meta-analysis.

BACKGROUND: Maintaining quality of life is a primary goal of palliative care (PC). Complementary interventions can help meet the needs of patients at the end of life. OBJECTIVES: This meta-analysis aims to (1) evaluate the feasibility, acceptability and fidelity of music and hypnosis interventions designed for patients in PC and (2) evaluate the impact of these interventions on pain, anxiety, sleep and well-being. METHODS: Relevant studies were sourced from major databases. We selected both randomised controlled trials (RCTs) and studies relying on pre-post design with details of the intervention(s). RESULTS: Four RCT and seven non-randomised pre-post studies met the inclusion criteria. Overall, the feasibility and acceptability of the interventions reached an adequate level of satisfaction. However, only three studies reported using a written protocol. The meta-analysis of RCT indicated a significant decrease in pain with an effect size of -0.42, p=0.003. The small number of RCT studies did not allow us to quantify the effects for other variables. Analyses of data from pre-post designs indicated a favourable outcome for pain, anxiety, sleep and well-being. CONCLUSION: Despite the limited number of studies included in our meta-analysis, hypnosis and music intervention in the context of PC shows promising results in terms of feasibility and acceptability, as well as improvements on pain, anxiety, sleep and well-being. The available studies are insufficient to compare the efficacy across interventions and assess the potential benefits of their combinations. These results underscore the importance of further research on well-described complementary interventions relying on hypnosis and music. PROSPERO REGISTRATION NUMBER: CRD-42021236610.

Effect of personalized musical intervention on burden of care in dental implant surgery: A pilot randomized controlled trial.

OBJECTIVE: To explore a personalized musical intervention's effect on burden of care during dental implants placement. METHODS: Randomized Controlled Trial in 24 dental implant surgery patients. A personalized music intervention (Music Care© application) or an audiobook control condition was administered. Burden of care (a composite outcome including self-reported anxiety, pain, and dissatisfaction felt during surgery), expected pain prior to surgery, pre- and post-surgery affect, memory of pain felt during surgery, and participants' emotional judgments of the music and audiobook listening were assessed. RESULTS: The personalized music intervention significantly reduced the burden of care for dental implant surgery (p = 0.02; d = 1.07). Both groups reported positive affect after surgery, but the music group felt better. The pain remembered after seven postoperative days was significantly lower in the music group (p = 0.02). Participants judged the music listened to during surgery as more relaxing and pleasant than the audiobook (p = 0.002 and p = 0.001, respectively). CONCLUSIONS: Personalized music intervention could be effective in decreasing patients' burden of care during dental implant surgery. These results need to be confirmed by a rigorous randomized control trial. CLINICAL SIGNIFICANCE: The burden of care associated with the pain and anxiety experienced during dental implant surgery can be reduced using a personalized and standardized music intervention. This approach may provide a simple complementary approach to improve surgical care in various settings.

Hypnosis to manage musculoskeletal and neuropathic chronic pain: A systematic review and meta-analysis.

This systematic review and meta-analysis aims to identify and quantify the current available evidence of hypnosis efficacy to manage pain in patients with chronic musculoskeletal and neuropathic pain. Randomized Control Trials (RCTs) with hypnosis and/or self-hypnosis treatment used to manage musculoskeletal and/or neuropathic chronic pain in adults and assessing pain intensity were included. Reviews, meta-analyses, non-randomized clinical trials, case reports and meeting abstracts were excluded. Five databases, up until May 13th 2021, were used to search for RCTs using hypnosis to manage chronic musculoskeletal and/or neuropathic pain. The protocol is registered on PROSPERO register (CRD42020180298) and no specific funding was received for this review. The risk of bias asessement was conducted according to the revised Cochrane risk of bias tool for randomized control trials (RoB 2.0). Nine eligible RCTs including a total of 530 participants were considered. The main analyses showed a moderate decrease in pain intensity (Hedge's g: -0.42; p = 0.025 after intervention, Hedge's g: -0.37; p = 0.027 after short-term follow-up) and pain interference (Hedge's g: -0.39; p = 0.029) following hypnosis compared to control interventions. A significant moderate to large effect size of hypnosis compared to controls was found for at 8 sessions or more (Hedge's g: -0.555; p = 0.034), compared to a small and not statistically significant effect for fewer than 8 sessions (Hedge's g: -0.299; p = 0.19). These findings suggest that a hypnosis treatment lasting a minimum of 8 sessions could offer an effective complementary approach to manage chronic musculoskeletal and neuropathic pain. Future research is needed to delineate the relevance of hypnosis in practice and its most efficient prescription.

Long-Term Efficacy of a Home-Care Hypnosis Program in Elderly Persons Suffering From Chronic Pain: A 12-Month Follow-Up.

BACKGROUND: Pain is a major public health concern in the aging population. However, medication brings about negative effects that compel healthcare professionals to seek alternative management techniques to alleviate pain. Hypnosis has been recognized as an effective technique to manage pain, but its long-term efficacy has yet to be examined in older adults. AIMS: The aim was to assess the effectiveness, over a 12-month period, of home-care hypnosis in elderly participants suffering from chronic pain. DESIGN: Real-life retrospective one-arm study with a 12-month follow-up. SETTINGS: Elderly Persons Suffering From Chronic Pain enrolled in a clinical health care program that offered home medical follow-up. PARTICIPANTS/SUBJECTS: Fourteen elderly women (mean age 81 years) with chronic pain participated in the home-care hypnosis program. All participants presented chronic pain (≥6 months) with average pain score >4/10. METHODS: Participants took part in seven 15-minute hypnosis sessions within 12 months. The Brief Pain Inventory questionnaire was used to evaluate pain perception and pain interference at baseline and at 3-, 6-, and 12-month follow-up period. RESULTS: Hypnosis home-care program significantly decreased pain perception and pain interference compared to baseline after 3 months (-29% and -40%, p < .001), and remained lower at 6 (-31% and -54%, p < .001) and 12 (-31% and -47%, p < .001) months. CONCLUSIONS: Seven sessions of 15 minutes allocated throughout a 12-month period produced clinically significant decreases in pain perception and pain interference. Hypnosis could be considered as an optimal additional way for health practitioners to manage chronic pain in an elderly population with long-term efficacy. This study offers a new long-term option to improve chronic pain management at home in elderly populations through a low-cost nonpharmacological intervention.

Feasibility and acceptability of hypnosis-derived communication administered by trained nurses to improve patient well-being during outpatient chemotherapy: a pilot-controlled trial.

PURPOSE: This pilot-controlled trial aimed to examine the feasibility and acceptability of hypnosis-derived communication (HC) administered by trained nurses during outpatient chemotherapy to optimize symptom management and emotional support - two important aspects of patient well-being in oncology. METHODS: The trial was conducted in two outpatient oncology units: (1) intervention site (usual care with HC), and (2) control site (usual care). Nurses at the intervention site were invited to take part in an 8-h training in HC. Participants' self-ratings of symptoms and emotional support were gathered at predetermined time points during three consecutive outpatient visits using the Edmonton Symptom Assessment Scale and the Emotional Support Scale. RESULTS: Forty-nine patients (24 in the intervention group, 25 in the control group) with different cancer types/stages were recruited over a period of 3 weeks and completed the study. All nurses (N = 10) at the intervention site volunteered to complete the training and were able to include HC into their chemotherapy protocols (about ± 5 min/intervention). Compared to usual care, patients exposed to HC showed a significant reduction in physical symptoms during chemotherapy. In contrast, perception of emotional support did not show any significant effect of the intervention. Participants exposed to HC report that the intervention helped them relax and connect on a more personal level with the nurse during chemotherapy infusion. CONCLUSIONS: Our results suggest that HC is feasible, acceptable, and beneficial for symptom management during outpatient chemotherapy. While future studies are needed, hypnosis techniques could facilitate meaningful contacts between cancer patients and clinicians in oncology. TRIAL REGISTRATION: Clinical Trial Identifier: NCT04173195, first posted on November 19, 2019.

The aversive value of pain in human decision-making.

BACKGROUND: In order to decide between avoiding pain or pursuing competing rewards, pain must be assigned an abstract value that can be traded against that of competing goods. To assess the relationship between subjectively perceived pain and its value, we conducted an experiment where participants had to accept or decline different intensities of painful electric shocks in exchange of monetary rewards. METHODS: Participants (n = 90) were divided into three groups that were exposed to different distributions of monetary rewards. Monetary offers ranged linearly from $0 to $5 or $10 in groups 1 and 2, respectively, and exponentially from $0 to $5 in group 3. Pain offers ranged from pain detection to pain tolerance thresholds. The value of pain was assessed by identifying the indifference points corresponding to a 50% chance of accepting a certain level of pain for a given monetary reward. RESULTS: The value of pain increased quadratically as a function of the anticipated pain intensity and was found to be relative to the mean and standard deviation of monetary offers. Moreover, decision times increased as a function of the intensity of accepted painful stimulations. Finally, inter-individual differences in psychological traits related to harm avoidance and persistence influenced the value of pain. CONCLUSIONS: This is the first demonstration that the value of pain follows a curvilinear function and is relative to the mean and standard deviation of competing monetary rewards. These new observations significantly contribute to our understanding of how pain is assigned value when making decisions between avoiding pain and obtaining rewards. SIGNIFICANCE: This work provides a description of the pain value function indicating how much people are willing to pay to avoid different intensities of pain. We found that the function was curvilinear, suggesting that the same unit of subjective pain has more value in the high vs. low pain range. Moreover, the pain value was influenced by the experimental manipulation of the rewards distribution and of the inter-individual differences in harm avoidance and persistence. Altogether, the present study provides a detailed account of how subjectively experienced pain is assigned value.

Multimodal Interventions Including Rehabilitation Exercise for Older Adults With Chronic Musculoskeletal Pain: A Systematic Review and Meta-analyses of Randomized Controlled Trials.

BACKGROUND AND PURPOSE: Musculoskeletal disorders (MSKDs) are the most common causes of disabilities for older adults. The aim of this systematic review and meta-analysis is to assess the effectiveness of multimodal interventions including exercise rehabilitation for older adults with chronic MSKDs. METHODS: A literature search was conducted up to February 2019 in 5 bibliographical databases to identify randomized controlled trials (RCTs) that compared multimodal interventions including exercise rehabilitation with usual medical care or no intervention. Randomized controlled trials were assessed with the Cochrane risk-of-bias tool. Meta-analyses were performed and pooled mean differences (MDs) or standardized mean differences (SMDs) were calculated. RESULTS: Sixteen RCTs (n = 2322 participants) were included. One RCT was considered at low risk of bias, 8 had some concerns of bias, and 7 had a high risk of bias. Participants suffered from hip or knee osteoarthritis (OA) (n = 12 RCTs), low back pain (LBP) (n = 2 RCTs) and generalized chronic pain (GCP) (n = 2 RCTs). Multimodal interventions were significantly more effective than usual care to decrease pain (visual analog scale, out of 10 points) in the short term, MD: -0.71 (95% confidence interval [CI] -1.08 to -0.34, n = 900), and in the long term: MD: -0.52 (95% CI -0.98 to -0.05, n = 575), but these differences are not considered clinically important. In terms of disabilities, multimodal interventions were also significantly more effective than usual care. The SMDs were -0.47 (95% CI -0.61 to -0.34, n = 903) and -0.29 (95% CI -0.46 to -0.13, n = 568) for OA trials in the short and long terms, respectively, and -0.47 (95% CI -0.81 to -0.12, n = 211) for LBP and GCP trials in the short term. The magnitude of these effects may be considered as small to moderate. CONCLUSION: Multimodal intervention including exercise rehabilitation combined with usual medical care is an efficacious therapeutic option to reduce disabilities in older adults with chronic MSKDs. A significant but not clinically important effect was observed for pain. The most beneficial component of the multimodal interventions in terms of education, exercises, or medication remains to be determined.