Pain Experience and Perception in the Obese Subject Systematic Review (Revised Version)

High Body Mass Index Disrupts the Homeostatic Effects of Pain Inhibitory Control in the Symptomatology of Patients With Fibromyalgia

This study examines the influence of body mass index (BMI) on the relationship between quantitative sensory testing measures and clinical characteristics in fibromyalgia syndrome (FMS). Utilizing BMI as a categorical covariate (≥25 or ≥30 kg/m²) in associations between quantitative sensory testing metrics (pain-60, conditioned pain modulation, and temporal summation of pain [TSP]) and FMS clinical features, we explored BMI's role as both a confounder (change-in-estimate criterion-change equal or higher than 10%) and effect modifier (interaction term). Significant interactions revealed overweight/obese BMI as a modifier in the relationship between conditioned pain modification and both depression and symptom impact, with a homeostatic relationship between better clinical profile and pain inhibitory response observed solely in the normal-weight group. Similar results were found for pain-60 and depression. Additionally, BMI ≥30 kg/m² modified TSP's effect on pain, demonstrating lower pain with increased TSP, exclusively in the nonobese group. This study highlights the significant role of BMI in moderating the relationships of important pain inhibitory control processes and pain intensity, depression, and the overall impact of FMS symptoms. Our results suggest that high BMI states disrupt the homeostatic effects of pain inhibition, reducing its salutogenic response in FMS participants. We discuss the mechanistic and therapeutic implications of targeting BMI in FMS clinical trials and the potential impact of this important relationship. PERSPECTIVE: This investigation highlights the disruptive influence of high BMI on pain inhibitory control in fibromyalgia, unbalancing clinical symptoms such as pain and depression. It underscores the necessity of integrating BMI considerations into therapeutic approaches to enhance pain management and patient outcomes.

Activation of α7 nicotinic receptors attenuated hyperalgesia and anxiety induced by palatable obesogenic diet withdrawal

Consumption of palatable food (PF) can alleviate anxiety, and pain in humans. Contrary, spontaneous withdrawal of long-term PF intake produces anxiogenic-like behavior and abnormal pain sensation, causing challenges to weight-loss diet and anti-obesity agents. Thus, we examined α7-nicotinic acetylcholine receptors (α7nAChR) involvement since it plays essential role in nociception and psychological behaviors.

METHODS

Adult male C57BL/6 mice were placed on a Standard Chow (SC) alone or with PF on intermittent or continuous regimen for 6 weeks. Then, mice were replaced with normal SC (spontaneous withdrawal). Body weight, food intake, and calories intake with and without the obesogenic diet were measured throughout the study. During PF withdrawal, anxiety-like behaviors and pain sensitivity were measured with PNU-282987 (α7nAChR agonist) administration.

RESULTS

Six weeks of SC + PF-intermittent and continuous paradigms produced a significant weight gain. PF withdrawal displayed hyperalgesia and anxiety-like behaviors. During withdrawal, PNU-282987 significantly attenuated hyperalgesia and anxiety-like behaviors.

CONCLUSION

The present study shows that a PF can increase food intake and body weight. Also, enhanced pain sensitivity and anxiety-like behavior were observed during PF withdrawal. α7nAChR activation attenuated anxiolytic-like behavior and hyperalgesia in PF abstinent mice. These data suggest potential therapeutic effects of targeting α7 nAChRs for obesity-withdrawal symptoms in obese subjects.

Adults with excess weight or obesity, but not with overweight, report greater pain intensities than individuals with normal weight: a systematic review and meta-analysis

Context

Over 1.9 billion adult people have overweight or obesity. Considered as a chronic disease itself, obesity is associated with several comorbidities. Chronic pain affects approximately 60 million people and its connection with obesity has been displayed in several studies. However, controversial results showing both lower and higher pain thresholds in subjects with obesity compared to individuals with normal weight and the different parameters used to define such association (e.g., pain severity, frequency or duration) make it hard to draw straight forward conclusions in the matter. The objective of this article is to examine the relationship between overweight and obesity (classified with BMI as recommended by WHO) and self-perceived pain intensity in adults.

Methods

A literature search was conducted following PRISMA guidelines using the databases CINAHL, Cochrane Library, EMBASE, PEDro, PubMed, Scopus and Web of Science to identify original studies that provide BMI values and their associated pain intensity assessed by self-report scales. Self-report pain scores were normalized and pooled within meta-analyses. The Cochrane's Q test and I2 index were used to clarify the amount of heterogeneity; meta-regression was performed to explore the relationship between each outcome and the risk of bias.

Results

Of 2194 studies, 31 eligible studies were identified and appraised, 22 of which provided data for a quantitative analysis. The results herein suggested that adults with excess weight (BMI ≥ 25.0) or obesity (BMI ≥ 30.0) but not with overweight (pre-obesity) alone (BMI 25.0-29.9), are more likely to report greater intensities of pain than individuals of normal weight (BMI 18.5-24.9). Subgroup analyses regarding the pathology of the patients showed no statistically significant differences between groups. Also, influence of age in the effect size, evaluated by meta-regression, was only observed in one of the four analyses. Furthermore, the robustness of the findings was supported by two different sensitivity analyses.

Conclusion

Subjects with obesity and excess weight, but not overweight, reported greater pain intensities than individuals with normal weight. This finding encourages treatment of obesity as a component of pain management. More research is required to better understand the mechanisms of these differences and the clinical utility of the findings.

Systematic Review Registration

https://doi.org/10.17605/OSF.IO/RF2G3, identifier OSF.IO/RF2G3.

Obesity Is Associated with Altered Rectal Sensitivity in Chronic Constipation

BACKGROUND

Defecation dysfunction may contribute to chronic constipation (CC), but the impact of obesity on anorectal physiology in CC remains unclear. We aimed to evaluate the relationship between obesity and anorectal function on physiologic testing in patients presenting with CC.

METHODS

This was a retrospective cohort study of consecutive adults who underwent high resolution anorectal manometry (HRAM) at a tertiary center for CC. Patient demographics, clinical history, surgical/obstetric history, medications, and HRAM results were reviewed. Patients were classified into obese (BMI > 30 kg/m2) vs non-obese (BMI < 30 kg/m2) groups at the time of HRAM. Fisher-exact/student t-test for univariate analyses and general linear regression for multivariable analysis were performed.

RESULTS

383 adults (mean 50.3 years; 85.8% female) with CC were included. On HRAM, patients with obesity had lower anal sphincter resting tone (37.3 vs 48.5 mmHg, p = 0.005) and maximum squeeze pressure (104.8 mmHg vs 120.0 mmHg, p = 0.043). No significant differences in dyssynergia (61% vs 53%, p = 0.294) and failed balloon expulsion (18% vs 25%, p = 0.381) were found between obese and non-obese groups. On balloon distention testing, the maximum tolerated (163.5 vs 147.6 mL, p = 0.042) and urge sensation (113.9 vs 103.7 mL, p = 0.048) volumes were significantly increased among patients with obesity. After adjusting for potential confounders, obesity remained independently associated with increased maximum tolerated volume (β-coefficient 13.7, p = 0.049).

CONCLUSION

Obesity was independently associated with altered rectal sensitivity among patients with CC. Altered rectal sensation may play an important role in CC among patients with obesity. Anorectal physiology testing should be considered to understand the pathophysiology and guide management.

Metabolic underpinnings of cancer-related fatigue

Cancer-related fatigue (CRF) is one of the most prevalent and detrimental complications of cancer. Emerging evidence suggests that obesity and insulin resistance are associated with CRF occurrence and severity in cancer patients and survivors. In this narrative review, we analyzed recent studies including both preclinical and clinical research on the relationship between obesity and/or insulin resistance and CRF. We also describe potential mechanisms for these relationships, though with the caveat that because the mechanisms underlying CRF are incompletely understood, the mechanisms mediating the association between obesity/insulin resistance and CRF are similarly incompletely delineated. The data suggest that, in addition to their effects to worsen CRF by directly promoting tumor growth and metastasis, obesity and insulin resistance may also contribute to CRF by inducing chronic inflammation, neuroendocrinological disturbance, and metabolic alterations. Furthermore, studies suggest that patients with obesity and insulin resistance experience more cancer-induced pain and are at more risk of emotional and behavioral disruptions correlated with CRF. However, other studies implied a potentially paradoxical impact of obesity and insulin resistance to reduce CRF symptoms. Despite the need for further investigation utilizing interventions to directly elucidate the mechanisms of cancer-related fatigue, current evidence demonstrates a correlation between obesity and/or insulin resistance and CRF, and suggests potential therapeutics for CRF by targeting obesity and/or obesity-related mediators.

The PATIENT Approach: A New Bundle for the Management of Chronic Pain

BACKGROUND

Chronic pain is one of the most challenging diseases for physicians as its etiology and manifestations can be extremely varied. Many guidelines have been published and many therapeutic options are nowadays available for the different types of pain. Given the enormous amount of information that healthcare providers must handle, it is not always simple to keep in mind all the phases and strategies to manage pain. We here present the acronym PATIENT (P: patient's perception; A: assessment; T: tailored approach; I: iterative evaluation; E: education; N: non-pharmacological approach; T: team), a bundle which can help to summarize all the steps to follow in the management of chronic pain.

METHODS

We performed a PubMed search with a list of terms specific for every issue of the bundle; only English articles were considered.

RESULTS

We analyzed the literature investigating these topics to provide an overview of the available data on each bundle's issue; their synthesis lead to an algorithm which may allow healthcare providers to undertake every step of a patient's evaluation and management.

DISCUSSION

Pain management is very complex; our PATIENT bundle could be a guide to clinicians to optimize a patient's evaluation and treatment.

The effect of body mass index on thoracic paravertebral block analgesia after video-assisted thoracoscopic surgery; a prospective interventional study

BACKGROUND

To investigate the effects of body mass index (BMI) on intensity postoperative pain in patients who underwent thoracic paravertebral block (TPVB) for postoperative analgesia after video-assissted thoracoscopic surgery (VATS).

METHODS

Patients aged 18-80 years, ASA I-III, and BMI 18-40 kg/m2 who underwent elective VATS were included in the study. The patients were divided into 3 groups according to their BMI levels. TPVB was performed under ultrasound-guidance at the fifth thoracic vertebrae, and 30 ml of 0.25% bupivacaine was injected. The patient-controlled analgesia (PCA) was performed by using morphine and multimodal analgesia was performed. As a rescue analgesic agent, 0.5 mg/kg tramadol was given to patients intravenously when a score of visual analog scale (VAS) at rest was ≥ 4. The primary outcome was determined as VAS scores at rest and cough. Secondary outcomes were determined as postoperative morphine consumption, additional analgesic requirement, and side effects.

RESULTS

The post-hoc test revealed that the VAS resting scores at the 4th hour (p: 0.007), 12th hour (p: 0.014), and 48th hour (p: 0.002) were statistically significantly lower in Group I compared to Group II. Additionally, VAS resting scores were also statistically significantly lower in Group I compared to Group III at all time points (p < 0.05). Similarly, the post-hoc test indicated that the VAS coughing scores at the 4th hour (p: 0.023), 12th hour (p: 0.011), and 48th hour (p: 0.019) were statistically significantly lower in Group I compared to Group II. Moreover, VAS coughing scores were statistically significantly lower in Group I compared to Group III at all time points (p < 0.001). Furthermore, there were statistically significant differences in terms of additional analgesic use between the groups (p: 0.001). Additionally, there was a statistically significant difference in terms of morphine consumption via PCA and morphine milligram equivalent consumption between the groups (p < 0.001).

CONCLUSIONS

Higher postoperative VAS scores with TPVB applied in obese patients and the consequent increase in additional analgesics and complications require more specific postoperative management in this patient group.

Opioid Analgesics after Bariatric Surgery: A Scoping Review to Evaluate Physiological Risk Factors for Opioid-Related Harm

The persisting use of opioids following bariatric surgery has emerged as a prevalent complication, heightening the probability of opioid-related harm (ORM), such as opioid-related fatalities and prescription opioid use disorder (OUD). A comprehensive review of PubMed literature from 1990 to 2023 was conducted to pinpoint physiological influences on postoperative ORM. As a result, we found that patients undertaking bariatric operations often exhibit an inherently higher risk for substance use disorders, likely attributable to genetic predisposition and related neurobiological changes that engender obesity and addiction-like tendencies. Furthermore, chronic pain is a common post-bariatric surgery complaint, and the surgical type impacts opioid needs, with increased long-term opioid use after surgeries. Additionally, the subjective nature of pain perception in patients with obesity can distort pain reporting and the corresponding opioid prescription both before and after surgery. Furthermore, the postoperative alterations to the gastrointestinal structure can affect the microbiome and opioid absorption rates, resulting in fluctuating systemic exposure to orally ingested opioids. The prospect of ORM development post-bariatric surgery appears amplified due to a preexisting susceptibility to addictive habits, surgically induced pain, modified gut-brain interaction and pain management and the changed pharmacokinetics post-surgery. Further research is warranted to clarify these potential risk variables for ORM, specifically OUD, in the bariatric population.

Improvement of Pain Symptoms in Musculoskeletal Diseases After Multimodal Spa Therapy in the Austrian Gastein Valley-A Study Based on Longitudinal Registry Data

Objective: The study aim was to investigate the course of pain in rest and motion in seven different rheumatic diseases (RMD), prior and after multimodal spa therapy including low-dose radon treatment and at 3-, 6-; and 9-month follow up. Methods: Complete data from the radon indication registry including information on 561 subjects with RMD were analysed to explore the association of timepoint of measurement with pain in rest and motion. For this purpose, linear regression models adjusted for RMD-type, age, sex and body mass index (BMI) were applied. Results: The mean age of the sample was 55 years, the average body mass index was 26.8, and 275 subjects were women. Pain scores were significantly improved at all-time points compared to baseline. Pain courses were different for each RMD with the largest improvement seen in fibromyalgia. Conclusion: Timing spa facility visits according to RMD-specific pain courses may result in sustained pain reduction.

Disinhibition augments thirst perception from two dehydrating stimuli in men

Physiological systems controlling water and energy ingestion are coordinated. Whether maladaptive eating behavior and appetite for water are linked is unknown. Thus, we sought to investigate the association between maladaptive eating and both thirst and water drinking behavior with two dehydrating conditions. Twenty-two lean men and 20 men with obesity (mean age 32.3 ± 8.4 years and 30.0 ± 11.1 years, respectively) completed the Three-Factor Eating Questionnaire (TFEQ) and Gormally Binge Eating Scale. On separate days, volunteers were dehydrated by a 2-h hypertonic saline infusion and a 24-h water deprivation, and thirst was measured on a 100-mm visual analogue scale (VAS) during each procedure. After each dehydrating condition, ad libitum water intake was measured. In the saline infusion, higher Disinhibition on the TFEQ was associated with thirst in the lean group (β = 4.2 mm VAS, p = 0.03) but not in the group with obesity (p = 0.51). In the water-deprivation condition, higher Disinhibition was also associated with thirst in the lean group (β = 5.6 mm VAS, p = 0.01) with the strength of relationship being 3.5-fold stronger than that observed in the group with obesity (β = 1.6 mm VAS, p = 0.0003). Hunger, Restraint, and binge-eating scores were not associated with thirst in either dehydrating condition (all p > 0.05). Maladaptive eating behaviors were not associated with ad libitum water intake (all p > 0.05). Disinhibition is associated with higher thirst perception in healthy weight individuals and may be attenuated in obesity. The characteristics of disinhibition which typically includes a heightened readiness to eat, may reflect a more general phenotype that also reflects a readiness to drink.

Lean Mass is Associated with, but Does Not Mediate Sex Differences in Pressure Pain Sensitivity in Healthy Adults

Background

Sex differences exist in pain sensitivity, however, the underlying mechanism(s) that explain these differences are not fully understood. Pain sensitivity has been shown to be influenced by body mass index, but limited data exist on the role of body composition on pain sensitivity. The purpose was to examine the influence of body composition on pain sensitivity in males and females.

Methods

This cross-sectional study design used pressure pain thresholds (PPT) of 87 participants (45 female) who were assessed in the vastus lateralis (leg PPT) and brachioradialis (arm PPT) using a pressure algometer. Fat and lean tissue were assessed via dual-energy X-ray absorptiometry (DXA). A two group by two limb, repeated measured ANOVA was used to assess differences between limbs and sex. Spearman correlations and hierarchical regression analyses were employed to determine the association between body composition and PPT.

Results

Males had higher PPTs then females (P<0.05) and had higher DXA assessed lean and lower levels fat mass (P<0.05). Total body and limb specific lean mass was associated with PPTs (r≥0.34; P<0.05). Hierarchical regression analysis revealed lean mass was a significant predictor of 8% of the variance in arm PPT (P<0.006) and 18% of the variance in leg PPT (P<0.001). However, lean mass was not found to statistically mediate the observed sex differences in PPT.

Conclusion

This finding suggests lean mass may play a previously unknown role in sex differences in pressure pain sensitivity. Future studies are needed to confirm this finding and a larger sample size is likely required to have sufficient power to perform the mediation analysis.

Validity of the Central Sensitization Inventory (CSI) through Rasch analysis in patients with knee osteoarthritis

INTRODUCTION/OBJECTIVE

Central sensitization (CS) is a known contributor to chronic pain in people with knee osteoarthritis (KOA) and is commonly measured by psychophysical testing or patient-reported methods such as the Central Sensitization Inventory (CSI). However, previous studies have shown a weak association between the two. We therefore sought to evaluate the validity of the CSI through Rasch analysis in patients with KOA.

METHOD

We performed a secondary analysis of a multicenter cohort study with patients with KOA consulting orthopedic surgeons. Rasch analysis was conducted considering person factors of age, sex, BMI, pain intensity, pain catastrophizing, and quantitative sensory test findings using pressure pain thresholds and temporal summation to assess how the CSI fits to the Rasch model (supporting validity). We used RUMM2030 software to model fit estimates, making adjustments as required to achieve model fit (P > 0.05).

RESULTS

Data from 293 patients were included (58.7% female, mean age 63.6 years, 49.1% obese) Initial evaluation with Rasch modelling indicated misfit. Eleven of 25 items on the CSI displayed disordered thresholds which were rescored by collapsing response categories until the thresholds demonstrated sequential progression. Reanalysis demonstrated persistent model misfit so a subtest was developed to address local dependency of 6 items. Thereafter, model fit was achieved (P = 0.071, indicating not differing from Rasch model) and acceptable unidimensionality (P = 0.068 with 95% CI 0.043-0.093).

CONCLUSIONS

The CSI was able to be fit to the Rasch model after rescoring while retaining all 25 items. The unidimensionality validates CS as measured by the CSI as a singular construct. Key Points • The Central Sensitization Inventory (CSI) was able to be fit to the Rasch model after rescoring while retaining all 25 items. • The unidimensionality of the CSI validates CS as a singular construct. • Our results suggest rescoring of the CSI for people with KOA, but it should be confirmed and replicated in larger samples prior to clinical use.

Immediate postoperative pain does not predict pain at home after ambulatory single-port sleeve gastrectomy

PURPOSE

Single-port sleeve gastrectomy (SPSG) is increasingly performed in an ambulatory setting. Pain intensity when returning home remains a problem. The challenge is to be able to predict the evolution of postoperative pain (POP) at home by using parameters collected during the hospital stay. This study aimed to investigate whether immediate POP in the postanesthesia care unit (PACU) can predict pain intensity 24 h after surgery.

METHODS

Single-center retrospective study in patients with obesity who underwent ambulatory SPSG. POP and opiate requirements during PACU stay were registered. Patients were followed up at home during the first 4 postoperative days. The primary outcome was the correlation between opiate requirements in the PACU and Numerical Rating Scale (NRS) at home 24 h after surgery. Secondly, logistic regression was used to identify risk factors for moderate/intense pain 24 h after surgery.

RESULTS

Ninety-four patients were included during the study period. Twenty-two patients had NRS > 3/10 24 h after surgery. No correlation was found between the total dose of morphine in the PACU and pain intensity 24 h after surgery (r² =  - 0.07; P = 0.49). No predictive factor for moderate/intense pain 24 h after surgery was found.

CONCLUSION

No correlation was found between opiate requirements in the PACU and pain at home 24 h after SPSG. Based on these results, it does not seem possible to predict intense pain at home from pain profile and morphine requirement during the immediate postoperative period.

Maternal High-Energy Diet during Pregnancy and Lactation Impairs Neurogenesis and Alters the Behavior of Adult Offspring in a Phenotype-Dependent Manner

Obesity is one of the biggest and most costly health challenges the modern world encounters. Substantial evidence suggests that the risk of metabolic syndrome or obesity formation may be affected at a very early stage of development, in particular through fetal and/or neonatal overfeeding. Outcomes from epidemiological studies indicate that maternal nutrition during pregnancy and lactation has a profound impact on adult neurogenesis in the offspring. In the present study, an intergenerational dietary model employing overfeeding of experimental mice during prenatal and early postnatal development was applied to acquire mice with various body conditions. We investigated the impact of the maternal high-energy diet during pregnancy and lactation on adult neurogenesis in the olfactory neurogenic region involving the subventricular zone (SVZ) and the rostral migratory stream (RMS) and some behavioral tasks including memory, anxiety and nociception. Our findings show that a maternal high-energy diet administered during pregnancy and lactation modifies proliferation and differentiation, and induced degeneration of cells in the SVZ/RMS of offspring, but only in mice where extreme phenotype, such as significant overweight/adiposity or obesity is manifested. Thereafter, a maternal high-energy diet enhances anxiety-related behavior in offspring regardless of its body condition and impairs learning and memory in offspring with an extreme phenotype.

Worst Pain Severity Profiles of Oncology Patients Are Associated With Significant Stress and Multiple Co-Occurring Symptoms

Little is known about the associations between pain, stress, and co-occurring symptoms in oncology patients. Purpose was to identify subgroups of patients with distinct worst pain profiles and evaluate for differences among the subgroups in demographic and clinical characteristics, as well as stress and symptom scores. Oncology outpatients (n = 1305) completed questionnaires prior to their second or third chemotherapy cycle. Worst pain intensity was assessed 6 times over 2 chemotherapy cycles using a 0 to 10 numeric rating scale. The 371 patients (28.4%) who had ≤1 occurrence of pain over the 6 assessments were classified as the None class. For the remaining 934 patients whose data were entered into the latent profile analysis, 3 distinct worst pain profiles were identified (ie Mild [12.5%], Moderate [28.6%], Severe [30.5%]). Compared to None class, Severe class had fewer years of education and a lower annual income; were less likely to be employed and married; less likely to exercise on a regular basis, had a higher comorbidity burden, and a worse functional status. Compared to None class, Severe class reported higher levels of general, disease-specific, and cumulative life stress and lower levels of resilience, as well as higher levels of depressive symptoms, anxiety, fatigue, sleep disturbance, and cognitive dysfunction. This study is the first to identify distinct worst pain profiles in a large sample of oncology patients receiving chemotherapy and associated risk factors. PERSPECTIVE: Unrelieved pain remains a significant problem for oncology patients receiving chemotherapy. High levels of stress and co-occurring symptoms contribute to a more severe pain profile in these patients.

Effect of early skin-to-skin contact after vaginal delivery on pain during perineal wound suturing: A randomized controlled trial

AIM

To evaluate whether early skin-to-skin contact at the end of the second stage of labor could relieve perineal wound suture pain.

METHODS

From March 2020 to November 2020, a total of 241 parturients with full-term single fetuses delivered through the vagina and who underwent episiotomy suture (n = 120) or perineal laceration repair (n = 121) in our hospital were included in the study. Parturients were categorized according to whether they received episiotomy suture or perineal laceration repair. They were randomized into an early skin contact group and a traditional neonatal care group. The primary outcome was pain, which was quantified by the Numerical Rating Scale, Visual Analog Scale, Verbal Rating Scale, Faces Pain Scale-Revised. The secondary outcomes were healing of the perineal wound, the maternal cooperation rate and operation time. The confounding factors of severe pain were analyzed.

RESULTS

Early skin-to-skin contact alleviated the pain of perineal laceration repair and episiotomy suture, shortened the operation time of episiotomy suture and improved the cooperation rate of parturients receiving suture. It had no effect on perineal wound healing, operation time, or the cooperation rate of perineal laceration repair. In addition to the operation and early skin contact, the occurrence of high-grade pain was also associated with prepregnancy body mass index, group B streptococcus (GBS) positive, and academic degree.

CONCLUSION

Early skin-to-skin contact at the end of the second stage of labor can alleviate pain and improve the delivery experience of vaginal delivery.

Physiological Changes and Pathological Pain Associated with Sedentary Lifestyle-Induced Body Systems Fat Accumulation and Their Modulation by Physical Exercise

A sedentary lifestyle is associated with overweight/obesity, which involves excessive fat body accumulation, triggering structural and functional changes in tissues, organs, and body systems. Research shows that this fat accumulation is responsible for several comorbidities, including cardiovascular, gastrointestinal, and metabolic dysfunctions, as well as pathological pain behaviors. These health concerns are related to the crosstalk between adipose tissue and body systems, leading to pathophysiological changes to the latter. To deal with these health issues, it has been suggested that physical exercise may reverse part of these obesity-related pathologies by modulating the cross talk between the adipose tissue and body systems. In this context, this review was carried out to provide knowledge about (i) the structural and functional changes in tissues, organs, and body systems from accumulation of fat in obesity, emphasizing the crosstalk between fat and body tissues; (ii) the crosstalk between fat and body tissues triggering pain; and (iii) the effects of physical exercise on body tissues and organs in obese and non-obese subjects, and their impact on pathological pain. This information may help one to better understand this crosstalk and the factors involved, and it could be useful in designing more specific training interventions (according to the nature of the comorbidity).

Racial and weight discrimination associations with pain intensity and pain interference in an ethnically diverse sample of adults with obesity: a baseline analysis of the clustered randomized-controlled clinical trial the goals for eating and moving (GEM) study

BACKGROUND

Everyday experiences with racial (RD) and weight discrimination (WD) are risk factors for chronic pain in ethnically diverse adults with obesity. However, the individual or combined effects of RD and WD on pain in adults with obesity is not well understood. There are gender differences and sexual dimorphisms in nociception and pain, but the effect of gender on relationships between RD, WD, and pain outcomes in ethnically diverse adults with obesity is unclear. Thus, the purposes of this study were to: 1) examine whether RD and WD are associated with pain intensity and interference, and 2) explore gender as a moderator of the associations between RD, WD, and pain.

METHODS

This is a baseline data analysis from a randomized, controlled clinical trial of a lifestyle weight-management intervention. Eligible participants were English or Spanish-speaking (ages 18-69 years) and had either a body mass index of ≥30 kg/m2 or ≥ 25 kg/m2 with weight-related comorbidity. RD and WD were measured using questions derived from the Experiences of Discrimination questionnaire (EOD). Pain interference and intensity were measured using the PROMIS 29 adult profile V2.1. Linear regression models were performed to determine the associations between WD, RD, gender, and pain outcomes.

RESULTS

Participants (n = 483) reported mild pain interference (T-score: 52.65 ± 10.29) and moderate pain intensity (4.23 ± 3.15). RD was more strongly associated with pain interference in women (b = .47, SE = .08, p < 001), compared to men (b = .14, SE = .07, p = .06). Also, there were no significant interaction effects between RD and gender on pain intensity, or between WD and gender on pain interference or pain intensity.

CONCLUSIONS

Pain is highly prevalent in adults with obesity, and is impacted by the frequencies of experiences with RD and WD. Further, discrimination against adults with obesity and chronic pain could exacerbate existing racial disparities in pain and weight management. Asking ethnically diverse adults with obesity about their pain and their experiences of RD and WD could help clinicians make culturally informed assessment and intervention decisions that address barriers to pain relief and weight loss.

TRIAL REGISTRATION

NCT03006328.

Pain sensitivity does not differ between obese and healthy weight individuals

Introduction

There is emerging evidence suggesting a relationship between obesity and chronic pain.

Objectives

The aim of this study was to determine whether pain-free obese individuals display altered pain responses to acute noxious stimuli, thus raising the possibility of greater pain sensitivity and potential susceptibility for chronic pain development.

Methods

Psychophysical and anthropometric data were collected from 38 individuals with an obese body mass index (BMI) classification (BMI ≥ 30) and 41 age/sex-matched individuals of a healthy BMI (BMI < 24.9). Because BMI may be an inaccurate index of obesity, additional anthropometric parameters of central adiposity and percent body fat were examined. Pain responses to suprathreshold noxious heat and cold stimuli were examined. Subjects provided pain intensity and unpleasantness ratings to noxious heat (49°C) applied at varying durations and locations (ventral forearm/lower leg). Cold pain ratings, thresholds, and tolerances were obtained after immersion of the hand in a cold-water bath (0-2°C). Between-group differences in pain responses, as well as relationships between pain responses and obesity parameters, were examined. Importantly, confounds that may influence pain such as anxiety, depression, impulsivity, sleepiness, and quality of life were assessed.

Results

No between-group differences in pain sensitivity to noxious heat and cold stimuli were found. No relationships were found between central adiposity or body fat (percentage or distribution) and pain responses to noxious heat or cold stimuli.

Conclusions

Obesity has minimal influence on pain sensitivity. Accordingly, it is unlikely that obesity alone increases susceptibility for chronic pain development through amplification of nociceptive processes.

Investigation of Correlations Between Pain Modulation Paradigms

OBJECTIVE

Endogenous pain modulation can be quantified through the use of various paradigms. Commonly used paradigms include conditioned pain modulation (CPM), offset analgesia (OA), spatial summation of pain (SSP), and temporal summation of pain (TSP), which reflect spatial and temporal aspects of pro- and antinociceptive processing. Although these paradigms are regularly used and are of high clinical relevance, the underlying physiological mechanisms are not fully understood.

DESIGN

The aim of this study is therefore to assess the association between these paradigms by using comparable protocols and methodological approaches.

SETTING

University campus.

SUBJECTS

Healthy and pain-free volunteers (n = 48) underwent psychophysical assessment of CPM, OA, SSP, and TSP (random order) at the same body area (volar nondominant forearm) with individualized noxious stimuli.

METHODS

CPM included heat stimuli before, during, and after a noxious cold-water bath, whereas for OA, three heat stimuli were applied: baseline trial, offset trial, and constant trial. For the SSP paradigm, two differently sized heat stimulation areas were evaluated, whereas for TSP, the first and last stimulus of 10 consecutive short heat stimuli were assessed. A computerized visual analog scale was used to continuously evaluate pain intensity. The magnitudes of all associations between all paradigm pairs were analyzed with Spearman's correlation, and individual influencing factors were assessed with a multivariate linear regression model.

RESULTS

Weak to moderate correlations among all four paradigms were found (P > 0.05), and no distinct influencing factors were identified.

CONCLUSIONS

A limited association between pain modulation paradigms suggests that CPM, OA, SSP, and TSP assess distinct aspects of endogenous analgesia with different underlying physiological mechanisms.

Diet, body weight and pain susceptibility - A systematic review of preclinical studies

Obesity has been associated with increased chronic pain susceptibility but causes are unclear. In this review, we systematize and analyze pain outcomes in rodent models of obesity as these can be important tools for mechanistic studies. Studies were identified using MEDLINE/PubMed and Scopus databases using the following search query: (((pain) OR (nociception)) AND (obesity)) AND (rat OR (mouse) OR (rodent))). From each eligible record we extracted the following data: species, strain, sex, pain/obesity model and main behavioral readouts. Out of 695 records 33 were selected for inclusion. 27 studies assessed nociception/acute pain and 17 studies assessed subacute or chronic pain. Overall genetic and dietary models overlapped in pain-related outcomes. Most acute pain studies reported either decreased or unaltered responses to noxious painful stimuli. However, decreased thresholds to mechanical innocuous stimuli, i.e. allodynia, were frequently reported. In most studies using subacute and chronic pain models, namely of subcutaneous inflammation, arthritis and perineural inflammation, decreased thresholds and/or prolonged pain manifestations were reported in obesity models. Strain comparisons and longitudinal observations indicate that genetic factors and the time course of the pathology might account for some of the discrepancies observed across studies. Two studies reported increased pain in animals subjected to high fat diet in the absence of weight gain. Pain-related outcomes in experimental models and clinical obesity are aligned indicating that the rodent can be an useful tool to study the interplay between diet, obesity and pain. In both cases weight gain might represent only a minor contribution to abnormal pain manifestation.

Diet can exert both analgesic and pronociceptive effects in acute and chronic pain models: a systematic review of preclinical studies

BACKGROUND

Although diet is an essential aspect of human health, the link between diet and pain is still not well understood. Preclinical animal research provides information to understand underlying mechanisms that allow identifying the needs for human research.

OBJECTIVES

This study aims to give a systematic overview of the current evidence from preclinical studies regarding the analgesic and pronociceptive effects of various diets in non-neuropathic, non-cancer, or non-visceral acute and chronic pain models.

STUDY DESIGN

A systematic Review.

SETTING

This study examined studies that investigate the analgesic and pronociceptive effects of various diets in non-neuropathic, non-cancer, or non-visceral acute and chronic pain models.

METHODS

This review was conducted following the PRISMA guidelines and was registered in PROSPERO with the registration number CRD42019133473. The certainty of evidence was examined by a modified GRADE approach.

RESULTS

After the screening process twenty-four eligible papers were included in this review. Nineteen studies examined acute pain, nine studies chronic inflammatory pain, and four studies assessed both acute and chronic pain models.

LIMITATIONS

Due to the heterogeneity of the included studies, a meta-analysis was not included in this study.

CONCLUSIONS

In animal models, excessive saturated, monounsaturated or omega-6 polyunsaturated fat ingestion and diets rich in fats and carbohydrates can decrease pain sensitivity in acute nociceptive pain, whereas it can induce mechanical allodynia and heat hyperalgesia in chronic inflammatory pain. Additionally, diets rich in anti-inflammatory ingredients, as well as a calorie-restricted diet can promote recovery from primary mechanical allodynia and heat hyperalgesia in chronic inflammatory pain.

The influence of bariatric surgery on hip and knee joint pain: a systematic review

Obesity increases the risk of osteoarthritis and the chance of needing joint replacement arthroplasty to reduce lower limb joint pain. Although nonsurgical weight loss interventions can reduce hip and knee joint pain, bariatric surgery may be a more feasible treatment option for people with severe obesity. However, it is unclear whether weight loss through bariatric surgery can positively influence hip and knee joint pain. Our objective was to evaluate the influence of bariatric surgery on hip and knee joint pain in people with obesity by conducting a systematic review of the literature. The PubMed, EMBASE, and Cochrane bibliographic databases were searched for studies published between 1947 and September 2019. Risk of bias of the identified studies was independently assessed by 2 reviewers using JBI's Critical Appraisal Checklist for Case Series and the Newcastle-Ottawa Scale. This review included 23 studies, all of which evaluated knee pain and 9 of which also evaluated hip pain. Reported results regarding hip pain intensity and the proportion of participants with hip pain were too limited to draw useful conclusions. Reported results regarding knee pain suggest that weight loss after bariatric surgery reduced knee pain intensity, as well as the proportion of participants with knee pain. The overall risk of bias of the majority of included studies (83%; n = 19) was judged to be unclear to high. Four small studies were judged as having a low risk of bias. Results of this systematic review suggest that bariatric surgery can positively influence hip and knee joint pain, but conclusive evidence is lacking because most of the included studies were judged as having plausible bias overall and in their key domains. Well-designed randomized controlled trials evaluating the influence of bariatric surgery on hip and knee joint pain using standardized joint pain measures are needed.

Internal Herniation Incidence After RYGB and the Predictive Ability of a CT Scan as a Diagnostic Tool

PURPOSE

The clinical diagnosis of an internal herniation (IH) after a Roux-en-Y Gastric Bypass (RYGB) remains difficult; therefore, performing a CT scan is usually part of the diagnostic process. The goal of this study was to assess the incidence of IH in patients with open and closed MD (mesenteric defect) and to study if the ability to diagnose an IH with a CT scan is different between these groups.

MATERIALS AND METHODS

IH was defined as a visible intestine through the mesenteric defect underneath the jejunojejunostomy and/or in the Petersen's space. CT scan outcomes were compared with the clinical diagnosis of an IH. Until 31 June 2013, standard care was to leave mesenteric defects (MDs) open; after this date, they were always closed.

RESULTS

The incidence of IH in the primarily non-closed group was 3.9%, and in the primarily closed group, this was 1.3% (p = 0.001). In group A (non-closed MD and CT), the sensitivity of the CT scan was 80%, and specificity was 0%. In group C (closed MD and CT), the sensitivity was 64.7%, and specificity was 89.5%. In group B (non-closed, no CT), an IH was visible in 58.7% of the cases and not in 41.3%. In group D (only a re-laparoscopy), an IH was visible in 34.3% of the cases and not in 65.7%.

CONCLUSIONS

Using the CT scan in suspected IH is not useful in if the MDs were not closed. If the MDs were closed, then a CT scan is predictive for the diagnosis IH.

Modulation of Pain Sensitivity by Chronic Consumption of Highly Palatable Food Followed by Abstinence: Emerging Role of Fatty Acid Amide Hydrolase

There is a strong relationship between palatable diet and pain sensitivity, and the cannabinoid and opioid systems might play an important role in this correlation. The palatable diet used in many animal models of obesity is the cafeteria (CAF) diet, based on human food with high sugar, salt, and fat content. In this study, we investigated whether long-term exposure to a CAF diet could modify pain sensitivity and explored the role of the cannabinergic system in this modification. Male Sprague–Dawley rats were divided into two groups: one fed with standard chow only (CO) and the other with extended access (EA) to a CAF diet. Hot plate and tail flick tests were used to evaluate pain sensitivity. At the end of a 40-day CAF exposure, EA rats showed a significant increase in the pain threshold compared to CO rats, finding probably due to up-regulation of CB1 and mu-opioid receptors. Instead, during abstinence from palatable foods, EA animals showed a significant increase in pain sensibility, which was ameliorated by repeated treatment with a fatty acid amide hydrolase inhibitor, PF-3845 (10 mg/kg, intraperitoneally), every other day for 28 days. Ex vivo analysis of the brains of these rats clearly showed that this effect was mediated by mu-opioid receptors, which were up-regulated following repeated treatment of PF-3845. Our data add to the knowledge about changes in pain perception in obese subjects, revealing a key role of CB1 and mu-opioid receptors and their possible pharmacological crosstalk and reinforcing the need to consider this modulation in planning effective pain management for obese patients.

Influence of increased body mass index on orthodontic tooth movement and related parameters in children and adolescents: A systematic review of longitudinal controlled clinical studies

Objectives:

To assess the impact of increased body mass index (BMI) on orthodontic tooth movement (OTM) and related parameters in children and adolescents.

Search sources:

A search of six electronic databases and manual searching were performed up to June 2019 without language and time restrictions.

Data selection:

Eligibility criteria were as follows: (1) longitudinal controlled clinical studies; (2) children and adolescents undergoing orthodontic therapy (OT); (3) no systemic diseases; (4) experimental group: patients with increased BMI; and (5) control group: patients with normal BMI.

Data extraction:

Screening, study selection and data extraction were performed; bias within studies was assessed using the Risk of Bias In Non-randomised Studies (ROBINS-I) tool.

Results:

Seven studies were included. One study showed that an increased BMI is associated with less wear-time of removable orthodontic appliances and one study found no significant association. One study showed that an increased BMI is associated with less cooperation during OT; however, not with the treatment results. One study reported higher pain experience during OT in adolescents with than without increased BMI. Two studies showed that increased BMI in adolescents is related to OTM, one with increased and one with decreased rates of OTM, respectively. One study reported an association between increased BMI and incidence of white spot lesions and gingivitis during OT. The ROBINS-I tool showed low to moderate risk of bias within studies.

Conclusions:

The influence of BMI on OTM and related parameters in children and adolescents remains debatable.

Deleterious Effects of Higher Body Mass Index on Subjective and Objective Measures of Chemotherapy-Induced Peripheral Neuropathy in Cancer Survivors

CONTEXT

Recent, albeit, limited evidence suggests that body mass index (BMI) may be a modifiable risk factor to reduce the deleterious effects of chemotherapy-induced peripheral neuropathy (CIPN) in cancer survivors.

OBJECTIVES

To evaluate for differences in demographic, clinical, pain, sensation, and balance characteristics among three BMI groups. We hypothesized that as BMI increased, survivors would report higher pain intensity scores and have significant decrements in measures of sensation and balance.

METHODS

A total of 416 survivors with CIPN were evaluated using subjective and objective measures of CIPN. Survivors were divided into three BMI groups (i.e., normal weight, overweight, and obese). Differences among the BMI groups were evaluated using parametric and nonparametric statistics.

RESULTS

Of the 416 survivors, 45.4% were normal weight, 32.5% were overweight, and 22.1% were obese. Compared with the normal-weight group, survivors in the other two groups had lower functional status scores, a higher comorbidity burden, higher pain intensity scores, and higher interference scores. In addition, compared with the normal-weight group, survivors in the other two BMI groups had significantly worse balance scores.

CONCLUSION

Our findings support the hypothesis that as BMI increased, pain sensation and balance characteristics worsened. Our findings suggest that nutritional counseling as well as exercise and weight management programs in survivors with CIPN may improve these clinically important problems.

Increased Pain Sensitivity in Obese Patients After Lung Cancer Surgery

Background: Obesity and cancer are recognized worldwide health threats. While there is no reported causal relationship, the increasing frequency of both conditions results in a higher incidence of obese patients who are being treated for cancer. Physiological data indicate that there is a relationship between obesity and susceptibility to pain; however, currently, there are no specific pharmacological interventions.

Objective: To evaluate the self-reported intensity of postoperative pain in obese and nonobese lung cancer who receive either thoracotomy or video-assisted thoracic surgery (VATS) surgical therapy.

Material and Methods: In 50 obese [mean body mass index (BMI) of 34.1 ± 3.2 kg/m²] and 62 nonobese (mean BMI of 24.9 ± 3 kg/m²) lung cancer patients, the intensity of pain was estimated every 4 h using a visual analog scale (VAS, 0 indicating no pain and 10 indicating “worst imaginable pain”) beginning shortly after surgery (Day O) and continuing until the day of discharge (Day D).

Results: The self-reported pain was more severe in obese than in nonobese patients, both at the time of the operation [Day O (4.5 ± 1.2 vs 3.4 ± 1.1; p < 0.0001)] and at the day of discharge [Day D (3.9 ± 1.4 vs 2.6 ± 0.9, p < 0.0001)]. This finding was consistent both in the patients after thoracotomy and after video-assisted thoracic surgery (VATS, p < 0.0001). The patients with severe pain shortly after surgery (VAS score >4) had significantly higher BMI (31.8 ± 5.6 kg/m²vs 28.8 ± 5.2 kg/m², p < 0.01) and were hospitalized longer than the remaining patients (13.0 ± 13.6 days vs 9.5 ± 3.6 days, p < 0.05).

Conclusion: The reported perception of pain in obese lung cancer patients is greater than in nonobese patients undergoing the same thoracic surgery. In obese patients, severe pain persisted longer. Pain management is an important consideration in the postoperative care of lung cancer patients, even more so with obese patients.

Short- and long-term impact of remifentanil on thermal detection and pain thresholds after cardiac surgery: A randomised controlled trial

BACKGROUND

The clinical relevance of the suggested hyperalgesic effects of remifentanil is still unclear, especially in the long term.

OBJECTIVE

The current study evaluated the impact of remifentanil on thermal thresholds 3 days and 12 months after surgery, measured with Quantitative Sensory Testing.

DESIGN

A single-blind, randomised controlled trial.

SETTING

A tertiary care teaching hospital in The Netherlands, from 2014 to 2016.

PATIENTS

A total of 126 patients aged between 18 and 85 years, undergoing cardiothoracic surgery via sternotomy (coronary artery bypass grafts and/or valve replacement) were included. Exclusion criteria were BMI above 35 kg m, history of cardiac surgery, chronic pain conditions, neurological conditions, allergy to opioids or paracetamol, language barrier and pregnancy.

INTERVENTIONS

Patients were allocated randomly to receive intra-operatively either a continuous remifentanil infusion or intermittent intra-operative fentanyl as needed in addition to standardised anaesthesia with propofol and intermittent intravenous fentanyl at predetermined time points.

MAIN OUTCOME MEASURES

Warm and cold detection and pain thresholds 3 days and 12 months after surgery. In addition the use of remifentanil, presence of postoperative chronic pain, age, opioid consumption and pre-operative quality of life were tested as a predictor for altered pain sensitivity 12 months after surgery.

RESULTS

Both warm and cold detection, and pain thresholds, were not significantly different between the remifentanil and fentanyl groups 3 days and 12 months after surgery (P > 0.05). No significant predictors for altered pain sensitivity were identified.

CONCLUSION

Earlier reports of increased pain sensitivity 1 year after the use of remifentanil could not be confirmed in this randomised study using Quantitative Sensory Testing. This indicates that remifentanil plays a minor role in the development of chronic thoracic pain. Still, the relatively high incidence of chronic thoracic pain and its accompanying impact on quality of life remain challenging problems.

TRIAL REGISTRATION

The study was registered at EudraCT (ref: 2013-000201-23) and ClinicalTrials.gov (https://clinicaltrials.gov/ct2/show/NCT02031016).

Analgesia nociception index for the assessment of pain in critically ill patients: a diagnostic accuracy study

Background

Behavioural pain tools are used in Intensive Care Unit (ICU) patients unable to self-report their pain-intensity but need sustained efforts to educate and train the ICU team because of the subjective nature of these clinical tools. This study measured the validity and performance of an electrophysiological monitoring tool based on the spectral analysis of heart rate variability, the Analgesia Nociception Index (ANI) which varies from 0 (minimal parasympathetic tone, maximal stress-response and pain) to 100 (maximal parasympathetic tone, minimal stress-response and pain).

Methods

Mean-ANI (ANIm) and Instant-ANI (ANIi) were continuously recorded then compared with the Behavioral Pain Scale (BPS) before, during and after routine care procedures in critically-ill non-comatose patients.

Results

969 assessments were performed in 110 patients. ANIi was the most discriminative pain tool. It was significantly correlated with BPS (r=-0.30; 95%CI -0.37 to -0.25; P<0.001). For an ANIi threshold of 42.5, the sensitivity, specificity, positive and negative predictive values were respectively 61.4%, 77.4%, 37.0%, and 90.4%. Compared with the BPS, ANIi had no significantly different ability to change during turning and tracheal-suctioning but changed significantly more during dressing change. ANIi increased independently with age, obesity and severity of illness, and controlled mechanical-ventilation, vasopressors use and analgesia. ANIi decreased independently when vigilance status and respiratory rate increased. ANIm demonstrated poor psychometric properties to detect pain.

Conclusions

Despite low sensitivity/specificity, ANIi≥43 had a Negative-Predictive-Value of 90%. Hence ANIi may be of highest benefit for excluding significant pain. A randomized controlled trial should compare sedation-analgesia protocols based on ANIi to presently recommended behavioural-pain-tools.

Safety analysis of proposed pegfilgrastim biosimilar in Phase I and Phase III studies

Aim: This analysis compares safety data for Sandoz proposed biosimilar (LA-EP2006) and reference pegfilgrastim from a Phase I pharmacokinetic/pharmacodynamic study in healthy volunteers (HVs) and two Phase III confirmatory studies in patients with breast cancer (BC; total n = 808). Patients & methods: Baseline characteristics were summarized, and event rates of bone pain and headache calculated. Results: HVs in the Phase I pharmacokinetic/pharmacodynamic study were generally younger, with lower mean body mass index, versus BC patients in PROTECT-1/-2. Bone pain was the most frequent adverse event with similar incidences with reference versus proposed biosimilar in all studies. Conclusion: No differences in adverse events were found between Sandoz proposed biosimilar and reference pegfilgrastim, notwithstanding some differences between HVs and BC patients.

DIAGNOSTIC VALUE OF C-REACTIVE PROTEIN AND THE INFLUENCE OF VISCERAL FAT IN PATIENTS WITH OBESITY AND ACUTE APPENDICITIS

BACKGROUND

The C reactive protein (CRP) is one of the most accurate inflammatory markers in acute appendicitis (AA). Obesity leads to a pro-inflammatory state with increased CRP, which may interfere with the interpretation of this laboratory test in AA.

AIM

To assess sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CRP in patients with AA and their correlation to body mass index (BMI) and body fat composition.

METHOD

This is a retrospective study based on clinical records and imaging studies of 191 subjects with histopathologically confirmed AA compared to 249 controls who underwent abdominal computed tomography (CT). Clinical and epidemiological data, BMI, and CRP values were extracted from medical records. CT scans were assessed for AA findings and body composition measurements.

RESULTS

CRP values increased according to patients' BMI, with varying sensitivity from 79.78% in subjects with normal or lean BMI, 87.87% in overweight, and 93.5% in individuals with obesity. A similar pattern was observed for NPV: an increase with increasing BMI, 69.3% in individuals with normal or lean BMI, 84.3% in overweight, and 91.3% in individuals with obesity. There was a positive correlation between CRP and visceral fat area in patients with AA.

CONCLUSIONS

Variations exist for sensitivity, specificity, PPV, and NPV values of CRP in patients with AA, stratified by BMI. An increase in visceral fat area is associated with elevated CRP across the BMI spectrum.

Managing severe pain and abuse potential: the potential impact of a new abuse-deterrent formulation oxycodone/naltrexone extended-release product

Proper management of severe pain represents one of the most challenging clinical dilemmas. Two equally important goals must be attained: the humanitarian/medical goal to relieve suffering and the societal/legal goal to not contribute to the drug abuse problem. This is an age-old problem, and the prevailing emphasis placed on one or the other goal has resulted in pendulum swings that have resulted in either undertreatment of pain or the current epidemic of misuse and abuse. In an effort to provide efficacious strong pain relievers (opioids) that are more difficult to abuse by the most dangerous routes of administration, pharmaceutical companies are developing products in which the opioid is manufactured in a formulation that is designed to be tamper resistant. Such a product is known as an abuse-deterrent formulation (ADF). ADF opioid products are designed to deter or resist abuse by making it difficult to tamper with the product and extracting the opioid for inhalation or injection. To date, less than a dozen opioid formulations have been approved by the US Food and Drug Administration to carry specific ADF labeling, but this number will likely increase in the coming years. Most of these products are extended-release formulations.

Efficacy of Noninvasive Brain Stimulation on Pain Control in Migraine Patients: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the efficacy of noninvasive brain stimulation (NIBS) on pain control in migraine patients.

BACKGROUND

Recent studies have used NIBS as an abortive and prophylactic treatment for migraine; however, its efficacy regarding meaningful clinical effects remains to be critically analyzed.

DESIGN

Systematic review of controlled clinical trials.

METHODS

Searches were conducted in six databases: MEDLINE (via PubMed), LILACS (via BIREME), CINAHL (via EBSCO), Scopus (via EBSCO), Web of Science, and CENTRAL. Two independent authors searched for randomized controlled clinical trials published through until January 2016 that involved the use of transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) in migraineurs. Studies which met the eligibility criteria were assessed and methodological quality was examined using the Cochrane tool for assessing risk of bias. Information about pain intensity (primary outcome), migraine attacks, painkiller intake, and adverse effects were extracted.

RESULTS

Eight studies were included in the quantitative analysis with 153 migraine patients that received NIBS and 143 sham NIBS. In overall meta-analysis, we did not find significant results for pain intensity (SMD: -0.61; CI: -1.35 to 0.13; P = .11), for migraine attacks (SMD: -0.44; 95%; CI: -1.15 to 0.26; P = .22), and for painkiller intake (SMD: -0.57; 95% CI: -1.21 to 0.07; P = .08). However, subgroup analysis considering only tDCS effects have demonstrated a decrease for pain intensity (SMD: -0.91; 95% CI: -1.79 to -0.03; P = .04), migraine attacks (SMD: -0.75; 95% CI: -1.25 to -0.24; P = .004), and painkiller intake (SMD: -0.64; 95% CI: -1.21 to -0.07; P = .03). Subgroup analysis for TMS did not reveal significant effects for any outcome.

CONCLUSION

Low or very low quality of evidence suggests that our primary outcome evaluation failed to find support for the superiority of NIBS over sham treatment. Although, subgroup analysis reveals that tDCS have moderate to high effects and could be a promising nonpharmacological alternative to pain control, mainly for painkiller intake reduction. However, there is a need for larger controlled trials with methodological rigor, which could increase the power of result inference.