CYP2D6-guided opioid therapy improves pain control in CYP2D6 intermediate and poor metabolizers: a pragmatic clinical trial

PURPOSE

CYP2D6 bioactivates codeine and tramadol, with intermediate and poor metabolizers (IMs and PMs) expected to have impaired analgesia. This pragmatic proof-of-concept trial tested the effects of CYP2D6-guided opioid prescribing on pain control.

METHODS

Participants with chronic pain (94% on an opioid) from seven clinics were enrolled into CYP2D6-guided (n = 235) or usual care (n = 135) arms using a cluster design. CYP2D6 phenotypes were assigned based on genotype and CYP2D6 inhibitor use, with recommendations for opioid prescribing made in the CYP2D6-guided arm. Pain was assessed at baseline and 3 months using PROMIS^® measures.

RESULTS

On stepwise multiple linear regression, the primary outcome of composite pain intensity (composite of current pain and worst and average pain in the past week) among IM/PMs initially prescribed tramadol/codeine (n = 45) had greater improvement in the CYP2D6-guided versus usual care arm (-1.01 ± 1.59 vs. -0.40 ± 1.20; adj P = 0.016); 24% of CYP2D6-guided versus 0% of usual care participants reported ≥30% (clinically meaningful) reduction in the composite outcome. In contrast, among normal metabolizers prescribed tramadol or codeine at baseline, there was no difference in the change in composite pain intensity at 3 months between CYP2D6-guided (-0.61 ± 1.39) and usual care (-0.54 ± 1.69) groups (adj P = 0.540).

CONCLUSION

These data support the potential benefits of CYP2D6-guided pain management.

Assessing Mentor Academy Program Effectiveness using Mixed Methods

The purpose of our study was to assess how an academic health center (AHC) mentor academy program affected mentor competence and optimized mentor-mentee relationship. Mixed methods were used to assess the effectiveness of an AHC mentor program at a clinical translational science institute (CTSI). Twenty biomedical research faculty mentors took a validated survey and submitted reflective writings to discover if they corroborated or refuted statistically significant survey results. There was significant improvement in participants' confidence of mentor skills, integral mentoring quality and the extent to which they fulfill mentees' expectations. Males provided constructive feedback and helped mentees develop goal strategies more often compared to females. Reflective writings supported these findings yet refuted two survey findings. The use of a mixed methods approach offers novel insight into how mentoring programs benefit translational research mentoring capacity building and raises questions about the sole use of surveys as evidence of program effectiveness.

Epigenetic aging is associated with clinical and experimental pain in community-dwelling older adults

Gerontological research reveals considerable interindividual variability in aging phenotypes, which has motivated research efforts to identify “aging biomarkers.” Aging biomarkers are used to calculate biological age, which are better predictors of disease risk and residual lifespan when compared to chronological age alone. Emerging evidence using the epigenetic clock as an aging biomarker supports highly reliable individualized predictions about future health. This study aimed to determine whether an epigenetic aging biomarker was associated with chronic pain in older adults (60–83 years old). A subset of participants (n = 29) in the Neuromodulatory Examination of Pain and Mobility Across the Lifespan study underwent a blood draw, demographic, psychological, cognitive, and pain assessments. We estimated Horvath’s epigenetic clock and calculated the difference between epigenetic age and chronological age that has been previously reported to predict overall mortality risk. Older individuals without chronic pain (n = 9) had significantly “younger” epigenetic age compared to those with chronic pain (n = 20, p < 0.05). Older epigenetic age was associated with greater pain during daily activities (r = 0.494, p = 0.010) and anatomical pain sites (r = 0.741, p < 0.001) but not pain frequency/duration. An older epigenetic age was also associated with higher vibratory detection thresholds (r = 0.490, p = 0.021), heat pain thresholds (r = −0.478, p = 0.028), and pressure pain thresholds at the trapezius (r = −0.571, p = 0.006) but not thermal detection, pressure pain at the quadriceps or pain inhibition (p’s > 0.05). Epigenetic aging was associated with greater emotional stability (r = −0.461, p = 0.027), conscientiousness (r = −0.549, p = 0.007), and lower extraversion (r = 0.414, p = 0.049) but not depression or affect (p’s > 0.05). Epigenetic aging was also associated with lower episodic (r = −0.698, p = 0.001) and working memory (r = −0.760, p < 0.001). Our findings suggest that chronic pain is associated with accelerated epigenetic aging in healthy, community-dwelling older individuals, and future studies with larger samples are needed to confirm our findings. An aging biomarker such as the epigenetic clock may help identify people with chronic pain at greater risk of functional decline and poorer health outcomes.

Resilience factors may buffer cellular aging in individuals with and without chronic knee pain

Telomere length, a measure of cellular aging, is inversely associated with chronic pain severity. While psychological resilience factors (e.g., optimism, acceptance, positive affect, and active coping) are associated with lower levels of clinical pain and greater physical functioning, it is unknown whether resilience may buffer against telomere shortening in individuals with chronic pain. Additionally, a broader conceptualization of resilience that includes social and biobehavioral factors may improve our understanding of the relationship between resilience, chronic pain, and health outcomes. In individuals with and without chronic knee pain, we investigated whether (1) psychological resilience would be positively associated with telomere length and if (2) a broader conceptualization of resilience including social and biobehavioral factors would strengthen the association. Seventy-nine adults, 45 to 85 years of age, with and without knee pain completed demographic, health, clinical pain, psychological, social, and biobehavioral questionnaires. Resilience levels were determined by summing the total number of measures indicating resilience based on published clinical ranges and norms. Blood samples were collected, and telomere length was determined. In regression analyses controlling for sex, race, age, and characteristic pain intensity, greater psychological resilience and psychosocial/biobehavioral resilience were associated with longer telomeres ( p = .0295 and p = .0116, respectively). When compared, psychosocial/biobehavioral resilience was significantly more predictive of telomere length than psychological resilience ( p < .0001). Findings are promising and encourage further investigations to enhance understanding of the biological interface of psychosocial and biobehavioral resilience factors in individuals with musculoskeletal chronic pain conditions.

Racial-Ethnic Differences in Osteoarthritis Pain and Disability: A Meta-Analysis

Osteoarthritis (OA), a leading cause of disability and pain, affects 32.5 million Americans, producing tremendous economic burden. Although some findings suggest that racial/ethnic minorities experience increased OA pain severity, other studies have shown conflicting results. This meta-analysis examined differences in clinical pain severity between African Americans (AAs) and non-Hispanic whites with OA. Articles were initially identified between October 1 and 5, 2016, and updated May 30, 2018, using PubMed, Web of Science, PsycINFO, and the Cochrane Library Database. Eligibility included English-language peer-reviewed articles comparing clinical pain severity in adult black/AA and non-Hispanic white/Caucasian patients with OA. Nonduplicate article abstracts (N = 1,194) were screened by 4 reviewers, 224 articles underwent full-text review, and 61 articles reported effect sizes of pain severity stratified by race. Forest plots of the standard mean difference showed higher pain severity in AAs for studies using the Western Ontario and McMasters Universities Osteoarthritis Index (0.57; 95% confidence interval [CI], 0.54-0.61) and non-Western Ontario and McMasters Universities Osteoarthritis Index studies (0.35, 95% CI, 0.23-0.47). AAs also showed higher self-reported disability (0.38, 95% CI, 0.22-0.54) and poorer performance testing (-0.58, 95% CI, -0.72 to -0.44). Clinical pain severity and disability in OA is higher among AAs and future studies should explore the reasons for these differences to improve pain management. PERSPECTIVE: This meta-analysis shows that differences exist in clinical pain severity, functional limitations, and poor performance between AAs and non-Hispanic whites with OA. This research may lead to a better understanding of racial/ethnic differences in OA-related pain.

Prescription Drug Monitoring Program Use: National Dental PBRN Results

INTRODUCTION

The American Dental Association recommends that dentists use a prescription drug monitoring program (PDMP) prior to prescribing an opioid for acute pain management.

OBJECTIVE

The objective of this study was to examine dentists' experiences using their state PDMP, as well as the impact that state-mandated registration policies, mandated use policies, and practice characteristics had on the frequency with which dentists used their PDMP.

METHODS

We conducted a web-based cross-sectional survey among practicing dentist members of the National Dental Practice-Based Research Network ( n = 805). The survey assessed prescribing practices for pain management and implementation of risk mitigation strategies, including PDMP use. Survey data were linked with network Enrollment Questionnaire data to include practitioner demographics and practice characteristics.

RESULTS

Nearly half of respondents ( n = 375, 46.6%) reported having never accessed a PDMP, with the most common reasons for nonaccess being lack of awareness ( n = 214, 57.1%) and lack of knowledge regarding registration and use ( n = 94, 25.1%). The majority of PDMP users reported the program to be very helpful (58.1%) or somewhat helpful (31.6%). Dentists reported that PDMP use most often did not change their intended prescribing behavior (40.2%), led them not to prescribe an opioid (33.5%), or led them to prescribe fewer opioid doses (25.5%). Presence of a mandated use policy was significantly associated with increased frequency of PDMP use across a variety of situations, including prior to 1) prescribing any opioid for pain management, 2) issuing refills, 3) prescribing to new patients, and 4) prescribing to patients deemed high risk.

CONCLUSION

Findings suggest that the majority of dentists find PDMPs helpful in informing their opioid-prescribing practices. Whereas the existence of a state-mandated use policy is a consistent predictor of dentists' PDMP use, outreach and education efforts may overcome key barriers to use identified in this study.

KNOWLEDGE TRANSFER STATEMENT

Findings from this national survey suggest that the majority of practicing dentists find PDMPs helpful in informing their opioid-prescribing practices; however, consistent PDMP use was not common. Whereas the existence of a state-mandated use policy is a consistent predictor of dentists' PDMP use, outreach and education efforts may overcome key barriers to use identified in this study.

Genetic and psychological factors interact to predict physical impairment phenotypes following exercise-induced shoulder injury

Background

We investigated interactions between genetic and psychological factors in predicting shoulder impairment phenotypes. We hypothesized that pro-inflammatory genes would display stronger relationships compared with pain-related genes when combined with psychological factors for predicting phenotypic changes.

Subjects and methods

Altogether, 190 participants completed a 5-day experimental protocol. An experimental shoulder injury model was used to induce physical impairment, and a priori selected genetic (pain-related, pro-inflammatory) and psychological (anxiety, depressive symptoms, pain catastrophizing, fear of pain, kinesiophobia) factors were included as predictors of interest. Impairment phenotypes were injury-induced deficits in range of motion (ROM) and strength. After controlling for age, sex, and race, genetic and psychological predictors were entered separately as main effects and interaction terms in regression models for each phenotype.

Results

Strong statistical evidence was provided for interactions between: 1) IL-1β (rs1143634) and fear of pain for predicting loss of shoulder flexion and abduction, 2) IL-1β (rs1143634) and anxiety for predicting loss of flexion, and 3) IL-1β (rs1143634) and depressive symptoms for predicting loss of internal rotation. In addition, the interaction between OPRM1 (rs1799971) and fear of pain as well as COMT (rs4818) and pain catastrophizing provided strong statistical evidence for predicting strength loss.

Conclusion

Pro-inflammatory gene variants contributed more to physical impairment with two single nucleotide polymorphisms (SNPs; IL-1β [rs1143634] and TNF/LTA [rs2229094]) interacting with psychological factors to predict six shoulder impairment phenotypes. In comparison, two pain-related gene SNPs (OPRM1 [rs1799971] and COMT [rs4818]) interacted with psychological factors to predict four shoulder impairment phenotypes (abduction: 5-day average loss; strength loss: 5-day average, peak, and relative loss).

Characteristics Associated With High-Impact Pain in People With Temporomandibular Disorder: A Cross-Sectional Study

High-impact (disabling) pain diminishes the quality of life and increases health care costs. The purpose of this study was to identify the variables that distinguish between high- and low-impact pain among individuals with painful temporomandibular disorder (TMD). Community-dwelling adults (N = 846) with chronic TMD completed standardized questionnaires that assessed the following: 1) sociodemographic characteristics, 2) psychological distress, 3) clinical pain, and 4) experimental pain. We used high-impact pain, classified using the Graded Chronic Pain Scale, as the dependent variable in logistic regression modeling to evaluate the contribution of variables from each domain. Cross-validated area under the receiver operating characteristic curve (AUC) quantified model discrimination. One-third of the participants had high-impact pain. Sociodemographic variables discriminated weakly between low- and high-impact pain (AUC = .61, 95% confidence interval [CI] = 0.57, 0.65), with the exception of race. An 18-variable model encompassing all 4 domains had good discrimination (AUC = 0.79, 95% CI = 0.75, 0.82), as did a simplified model (sociodemographic variables plus catastrophizing, jaw limitation, and number of painful body sites) (AUC = 0.79, 95% CI = 0.76, 0.82). Duration of pain, sex, and experimental pain testing results were not associated. The characteristics that discriminated most effectively between people with low- and high-impact TMD pain included clinical pain features and the ability to cope with pain. PERSPECTIVE: This article presents the results of a multivariable model designed to discriminate between people with high- and low-impact pain in a community-based sample of people with painful chronic TMD. The findings emphasize the importance of catastrophizing, jaw limitation, and painful body sites associated with pain-related impact.

Bayesian analysis of the effect of transcranial direct current stimulation on experimental pain sensitivity in older adults with knee osteoarthritis: randomized sham-controlled pilot clinical study

Purpose

Previous studies have indicated that transcranial direct current stimulation (tDCS) with the anode over the motor cortex and the cathode over the contralateral supraorbital region is effective in reducing clinical pain in patients with chronic pain, but these studies have not focused on experimental pain sensitivity. Therefore, the aim of this study was to examine the effect of tDCS on experimental pain sensitivity in older adults with knee osteoarthritis (OA).

Patients and methods

Forty community-dwelling participants aged 50–70 years with knee OA pain were randomly assigned to receive five daily sessions of 2 mA tDCS for 20 minutes (n = 20) or sham tDCS (n = 20) using a parallel group design. A multimodal quantitative sensory testing battery was completed, including heat pain, pressure pain threshold (PPT), punctate mechanical pain, and conditioned pain modulation (CPM).

Results

The active tDCS group showed greater increases in heat pain thresholds and tolerances, PPTs, and CPM, and reductions in punctate pain. In addition, beneficial changes in experimental pain measures were associated with reductions in clinical pain. Future studies are needed to extend these findings to better understand the underlying mechanisms of tDCS as well as to optimize treatment parameters including number and duration of stimulation sessions.

Conclusion

Our findings demonstrate that tDCS reduces experimental pain sensitivity, and these beneficial changes in experimental pain measures were associated with reductions in clinical pain.

Single Nucleotide Polymorphism in the COL11A2 Gene Associated with Heat Pain Sensitivity in Knee Osteoarthritis

Pain is one of the most prominent symptoms of osteoarthritis. However, there is often discordance between the pain experienced by individuals with osteoarthritis and the degree of articular pathology. This suggests that individual differences, including genetic variability in the central processing of nociceptive stimuli, may impact the presentation of osteoarthritis. Here, we show that the single nucleotide polymorphism rs16868943 in the collagen gene COL11A2 is significantly associated with lowered heat pain tolerance on the arm in participants with knee osteoarthritis (P = 1.21 × 10⁻⁶, P = 0.0053 after Bonferroni correction, beta = −3.42). A total of 161 knee osteoarthritis participants were included and evaluated for heat, punctate and pressure pain sensitivity of the affected knee and the ipsilateral arm. Each participant was genotyped for 4392 single nucleotide polymorphisms in genes implicated in pain perception, inflammation and mood and tested for association with pain sensitivity. The minor A allele of single nucleotide polymorphism rs16868943 was significantly associated with lower arm heat pain tolerance after correction for age, gender, race, and study site. This single nucleotide polymorphism was also nominally associated with other measures of heat pain sensitivity, including lowered knee heat pain tolerance (P = 1.14 × 10⁻⁵, P = 0.05 after Bonferroni correction), lowered arm heat pain threshold (P = 0.0039, uncorrected) and lowered knee heat pain threshold (P = 0.003, uncorrected). Addition of genotypes from 91 participants without knee pain produced a significant interaction between knee osteoarthritis status and the rs16868943 single nucleotide polymorphism in heat pain tolerance (P = 1.71 × 10⁻⁵), such that rs16868943 was not associated with heat pain tolerance in participants without knee pain (P = 0.12, beta = 1.3). This is the first study to show genetic association with heat pain tolerance in individuals with osteoarthritis. The association is specific to participants who have already developed knee osteoarthritis, suggesting that the COL11A2 gene, which has previously been associated with familial osteoarthritis, may play a role in pain sensitization after the development of osteoarthritis.

Sex Differences in Brain Regions Modulating Pain Among Older Adults: A Cross-Sectional Resting State Functional Connectivity Study

Objective

A long-standing hypothesis is that when compared with males, females may be at increased risk of experiencing greater pain sensitivity and unpleasantness. The purpose of this study was to examine sex differences in pain psychophysics and resting state functional connectivity (RSFC) in core pain regions in an age- and sex-matched sample of healthy older adults.

Design

Between groups, cross-sectional.

Setting

Vanderbilt University and Medical Center.

Subjects

The sample in the analyses reported here consisted of 19 cognitively intact males matched with 19 cognitively intact females of similar ages (median ages: females = 70 years, males = 68 years).

Methods

Psychophysical assessment of experimental thermal pain and RSFC.

Results

There were no significant differences in perceptual thresholds or unpleasantness ratings in response to thermal stimuli. Older males showed greater RSFC between the affective and sensory networks and between affective and descending modulatory networks. Conversely, older females showed greater RSFC between the descending modulatory network and both sensory and affective networks. The strongest evidence for sex differences emerged in the associations of thermal pain with RSFC between the anterior cingulate cortex (ACC) and amygdala and between the ACC and periaqueductal gray matter in older females relative to older males.

Conclusions

We found no differences in pain sensitivity or pain affect between older males and older females. Additionally, we found that older females exhibited a greater association between thermal pain sensitivity and RSFC signal between regions typically associated with pain affect and the descending modulatory system. One interpretation of these findings is that older females may better engage the descending pain modulatory system. This better engagement possibly translates into older females having similar perceptual thresholds for temperature sensitivity and unpleasantness associated with mild and moderate pain. These findings contrast with studies demonstrating that younger females find thermal pain more sensitive and more unpleasant.

Examining the Impact of a Resilience-Based Hope Intervention on Pain-Evoked Cortisol Response

Temporomandibular disorder (TMD) is an orofacial pain condition often resulting in functional impairment and pain-related disability. Given the relationship between stress and pain in TMD, it has been suggested that dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis (e.g., cortisol responsivity) could contribute to the onset and maintenance of the condition. Research has shown that therapies to control pain and stress can improve quality of life in patients with persistent pain, with recent evidence supporting resilience as a potential target of intervention. However, no studies have systematically examined whether a resilience intervention has efficacy in modulating neuroendocrine functioning in TMD. Therefore, the primary objective of this pilot study was to investigate the effects of a resilience-based hope intervention on pain-evoked cortisol levels in individuals with TMD. Twenty-nine participants were randomized to a 3-session intervention intended to increase hope or a control intervention targeting pain and stress education. Prior to and after the intervention, participants attended two experimental sessions whereby salivary cortisol was obtained after the induction of a painful, cold-water procedure. While there were no intervention group differences in pain-evoked cortisol response, greater situational and dispositional hope were associated with lower levels of cortisol. Overall, findings suggest that positive emotional resources may attenuate heightened neuroendocrine activity; however, further research is needed to determine the physiological benefits of resilience-oriented therapies.

Depression and Pain in Asian and White Americans With Knee Osteoarthritis

Few studies have examined the underlying psychosocial mechanisms of pain in Asian Americans. Using the biopsychosocial model, we sought to determine whether variations in depression contribute to racial group differences in symptomatic knee osteoarthritis pain between Asian Americans and non-Hispanic white Americans. The sample consisted of 100 participants, including 50 Asian Americans (28 Korean Americans, 9 Chinese Americans, 7 Japanese Americans, 5 Filipino Americans, and 1 Indian American) and 50 age- and sex-matched non-Hispanic white Americans with symptomatic knee osteoarthritis pain. The Centers for Epidemiologic Studies Depression Scale was used to assess symptoms of depression, and the Western Ontario and McMaster Universities Osteoarthritis Index and the Graded Chronic Pain Scale were used to measure clinical pain. In addition, quantitative sensory testing was used to measure experimental sensitivity to heat- and mechanically-induced pain. The results indicated that higher levels of depression in Asian Americans may contribute to greater clinical pain and experimental pain sensitivity. These findings add to the growing literature regarding ethnic and racial differences in pain and its associated psychological conditions, and additional research is warranted to strengthen these findings.

PERSPECTIVE

This article shows the contribution of depression to clinical pain and experimental pain sensitivity in Asian Americans with knee osteoarthritis. Our results suggest that Asian Americans have higher levels of depressive symptoms and that depression plays a relevant role in greater clinical pain and experimental pain sensitivity in Asian Americans.

Overlapping Chronic Pain Conditions: Implications for Diagnosis and Classification

There is increasing recognition that many if not most common chronic pain conditions are heterogeneous with a high degree of overlap or coprevalence of other common pain conditions along with influences from biopsychosocial factors. At present, very little attention is given to the high degree of overlap of many common pain conditions when recruiting for clinical trials. As such, many if not most patients enrolled into clinical studies are not representative of most chronic pain patients. The failure to account for the heterogeneous and overlapping nature of most common pain conditions may result in treatment responses of small effect size when these treatments are administered to patients with chronic overlapping pain conditions (COPCs) represented in the general population. In this brief review we describe the concept of COPCs and the putative mechanisms underlying COPCs. Finally, we present a series of recommendations that will advance our understanding of COPCs.

PERSPECTIVE

This brief review describes the concept of COPCs. A mechanism-based heuristic model is presented and current knowledge and evidence for COPCs are presented. Finally, a set of recommendations is provided to advance our understanding of COPCs.

Efficacy of transcranial direct current stimulation over primary motor cortex (anode) and contralateral supraorbital area (cathode) on clinical pain severity and mobility performance in persons with knee osteoarthritis: An experimenter- and participant-blinded, randomized, sham-controlled pilot clinical study

BACKGROUND

Previous studies indicate that transcranial direct current stimulation (tDCS) with anode over motor cortex (M1) and cathode over contralateral supraorbital region (SO) may be effective in reducing pain, but these studies are limited in number and have not focused on older adults with osteoarthritis (OA).

OBJECTIVE

To evaluate the preliminary efficacy and safety of M1-SO applied tDCS on clinical pain severity and mobility performance in adults with knee OA pain.

METHODS

Forty 50- to 70-year-old community-dwelling participants with knee OA were randomly assigned to receive five daily sessions of 2 mA tDCS for 20 min (n = 20) or sham tDCS (n = 20). We measured clinical pain severity via Numeric Rating Scale, Western Ontario and McMaster Universities Osteoarthritis Index, and Short-Form McGill Pain Questionnaire. In addition, we measured mobility performance using the 6-Minute Walk Test and the Short Physical Performance Battery. Moreover, we obtained a sensation/safety questionnaire and measured cognition changes using the PROMIS-Applied Cognition-Abilities-Short Form 8a.

RESULTS

Active tDCS over M1-SO significantly reduced Numeric Rating Scale of pain compared to sham tDCS after completion of the five daily sessions, and remained up to three weeks. No other measures were significantly different from sham. Participants tolerated tDCS over M1-SO well without serious adverse effects or cognition changes.

CONCLUSION

Although not consistent in all pain measurements, our findings demonstrate promising clinical efficacy for reduction in pain perception for older adults with knee OA.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT02512393.

Loss of Temporal Inhibition of Nociceptive Information Is Associated With Aging and Bodily Pain

An age-related decline in endogenous pain inhibitory processes likely places older adults at an increased risk for chronic pain. Limited research indicates that older adults may be characterized by deficient offset analgesia, an inhibitory temporal sharpening mechanism that increases the detectability of minor decreases in noxious stimulus intensity. The primary purpose of the study was to examine age differences in offset analgesia in community-dwelling younger, middle-aged, and older adults. An additional aim of the study was to determine whether the magnitude of offset analgesia predicted self-reported bodily pain. Eighty-seven younger adults, 42 middle-aged adults, and 60 older adults completed 4 offset analgesia trials and 3 constant temperature trials in which a noxious heat stimulus was applied to the volar forearm for 40 seconds. The offset trials consisted of 3 continuous phases: an initial 10-second painful stimulus, either a 1.0°C or .4°C increase in temperature from the initial 10-second painful stimulus for 10 seconds, and either a 1.0°C or .4°C decrease back to the initial testing temperature for 20 seconds. During each trial, subjects rated pain intensity continuously using an electronic visual analog scale (0-100). All subjects also completed the Short-Form Health Survey-36 including the Bodily Pain subscale. The results indicated that older and middle-aged adults showed reduced offset analgesia compared with younger adults in the 1.0°C and .4°C offset trials. Furthermore, the magnitude of offset analgesia predicted self-reported bodily pain, with those exhibiting reduced offset analgesia reporting greater bodily pain. Dysfunction of this endogenous inhibitory system could increase the risk of developing chronic pain for middle-aged and older adults.

PERSPECTIVE

Older and middle-aged adults showed reduced offset analgesia compared with younger adults. The significant association between reduced offset analgesia and pain in daily life supports the notion that pain modulatory deficits are associated with not just a chronic pain condition but with the experience of pain in general.

Physical performance and movement-evoked pain profiles in community-dwelling individuals at risk for knee osteoarthritis

BACKGROUND

Knee pain associated with osteoarthritis is a significant contributor to decreased physical function. Recent evidence supports the inter-individual heterogeneity associated with knee pain presentation, but whether there is similar heterogeneity in physical performance among these individuals has not been previously examined. The aim of the present study was to characterize the variability in physical performance profiles and the pain evoked by their performance (i.e., movement-evoked pain).

METHODS

In a secondary analysis of the community-based study Understanding Pain and Limitations in Osteoarthritic Disease (UPLOAD), individuals (n=270) completed functional, pain, psychological, and somatosensory assessments. Hierarchical cluster analysis was used to derive physical function profiles that were subsequently compared across several clinical, psychological and experimental pain measures.

RESULTS

Our results support the hypothesis that among persons with knee OA pain, three different physical performance profiles exist with varying degrees of movement-evoked pain. Even as all three groups experienced moderate to severe levels of spontaneous knee pain, those individuals with the most severe movement-evoked pain and lowest physical functional performance also had the least favorable psychological characteristics along with increased mechanical pain sensitivity and temporal summation.

CONCLUSIONS

Our findings support the need for the assessment and consideration of movement-evoked pain during physical performance tasks as these have the potential to increase the value of functional and pain assessments clinically. The identification of the mechanisms driving pain burden within homogeneous groups of individuals will ultimately allow for targeted implementation of treatments consistent with a biopsychosocial model of pain.

Epiregulin and EGFR interactions are involved in pain processing

The EGFR belongs to the well-studied ErbB family of receptor tyrosine kinases. EGFR is activated by numerous endogenous ligands that promote cellular growth, proliferation, and tissue regeneration. In the present study, we have demonstrated a role for EGFR and its natural ligand, epiregulin (EREG), in pain processing. We show that inhibition of EGFR with clinically available compounds strongly reduced nocifensive behavior in mouse models of inflammatory and chronic pain. EREG-mediated activation of EGFR enhanced nociception through a mechanism involving the PI3K/AKT/mTOR pathway and matrix metalloproteinase-9. Moreover, EREG application potentiated capsaicin-induced calcium influx in a subset of sensory neurons. Both the EGFR and EREG genes displayed a genetic association with the development of chronic pain in several clinical cohorts of temporomandibular disorder. Thus, EGFR and EREG may be suitable therapeutic targets for persistent pain conditions.

Accelerated aging in adults with knee osteoarthritis pain: consideration for frequency, intensity, time, and total pain sites

INTRODUCTION

Individuals with osteoarthritis (OA) show increased morbidity and mortality. Telomere length, a measure of cellular aging, predicts increased morbidity and mortality. Telomeres shorten with persisting biological and psychosocial stress. Living with chronic OA pain is stressful. Previous research exploring telomere length in people with OA has produced inconsistent results. Considering pain severity may clarify the relationship between OA and telomeres.

OBJECTIVES

We hypothesized that individuals with high OA chronic pain severity would have shorter telomeres than those with no or low chronic pain severity.

METHODS

One hundred thirty-six adults, ages 45 to 85 years old, with and without symptomatic knee OA were included in the analysis. Peripheral blood leukocyte telomere length was measured, and demographic, clinical, and functional data were collected. Participants were categorized into 5 pain severity groups based on an additive index of frequency, intensity, time or duration, and total number of pain sites (FITT). Covariates included age, sex, race or ethnicity, study site, and knee pain status.

RESULTS

The no or low chronic pain severity group had significantly longer telomeres compared with the high pain severity group, P = 0.025. A significant chronic pain severity dose response emerged for telomere length, P = 0.034. The FITT chronic pain severity index was highly correlated with the clinical and functional OA pain measures. However, individual clinical and functional measures were not associated with telomere length.

CONCLUSION

Results demonstrate accelerated cellular aging with high knee OA chronic pain severity and provide evidence for the potential utility of the FITT chronic pain severity index in capturing the biological burden of chronic pain.

Increased spatial dimensions of repetitive heat and cold stimuli in older women

Protocols of temporal summation (TS) of pain typically involve the delivery of brief repetitive noxious pulses of a constant intensity while measuring the perceived intensity of pain after each pulse. The size percept of noxious repetitive stimulation has been poorly characterized. Furthermore, no studies have investigated age differences in TS of cold pain. The current study examined TS of pain intensity and the perceived size of the painful area during repetitive noxious heat and cold pulses in healthy younger (n = 104) and older adults (n = 40). Trials of 10 brief repetitive noxious heat or cold pulses were delivered to the upper extremities. Participants rated the perceived size of the painful area or intensity of pain after each pulse. The magnitude of change for the size percept and intensity for pain were calculated for each trial. The results indicated that older adults experienced greater TS of the size percept of cold stimuli compared with younger adults. Additionally, older women experienced greater TS of the size percept of heat stimuli compared with older men and all younger participants. No overall age or sex differences were found in the TS of pain intensity for cold or heat trials. These results suggest dysfunctional modulation of the spatial percept of the painful stimuli by older adults, and in particular older women, during repetitive noxious thermal pulses.

Stress-related psychological symptoms contribute to axial pain persistence after motor vehicle collision: path analysis results from a prospective longitudinal study

Posttraumatic stress disorder (PTSD) symptoms and pain after traumatic events such as motor vehicle collision (MVC) have been proposed to be mutually promoting. We performed a prospective multicenter study that enrolled 948 individuals who presented to the emergency department within 24 hours of MVC and were discharged home after evaluation. Follow-up evaluations were completed 6 weeks, 6 months, and 1 year after MVC. Path analysis results supported the hypothesis that axial pain after MVC consistently promotes the maintenance of hyperarousal and intrusive symptoms, from the early weeks after injury through 1 year. In addition, path analysis results supported the hypothesis that one or more PTSD symptom clusters had an influence on axial pain outcomes throughout the year after MVC, with hyperarousal symptoms most influencing axial pain persistence in the initial months after MVC. The influence of hyperarousal symptoms on pain persistence was only present among individuals with genetic vulnerability to stress-induced pain, suggesting specific mechanisms by which hyperarousal symptoms may lead to hyperalgesia and allodynia. Further studies are needed to better understand the specific mechanisms by which pain and PTSD symptoms enhance one another after trauma, and how such mechanisms vary among specific patient subgroups, to better inform the development of secondary preventive interventions.

Causal Mediation in the Development of Painful Temporomandibular Disorder

We explored causal mediation of sleep quality and perceived stress in development of painful temporomandibular disorder (TMD). Sleep quality and perceived stress were assessed at baseline and quarterly intervals thereafter in 2,737 initially TMD-free adults in the Orofacial Pain Prospective Evaluation and Risk Assessment study (OPPERA) prospective cohort study. During follow-up, incident TMD cases were classified using research diagnostic criteria. Mediation analysis was conducted using a weighted Cox proportional hazards regression model that estimated hazard ratios (HRs) and 95% confidence limits (CL) of first-onset TMD. Models determined whether: 1) poor sleep quality during follow-up mediated the effect of baseline perceived stress on first-onset TMD, and 2) perceived stress during follow-up mediated the effect of baseline poor sleep quality on first-onset TMD. In both analyses, the total effect was decomposed into natural direct and indirect effects. Poor baseline sleep quality led to heightened perceived stress that then contributed to TMD development. When the total effect of poor sleep quality (HR = 2.10, CL = 1.76, 2.50) was decomposed, 34% of its effect was mediated by perceived stress (indirect effect HR = 1.29, CL = 1.06, 1.58). The effect of perceived stress on first-onset TMD was not mediated by sleep quality. Improving sleep may avert escalation of stress, limiting effects of both factors on TMD development.

PERSPECTIVE

Causal mediation analysis highlights mechanisms by which poor sleep quality promotes development of TMD. First, poor sleep quality exerts a direct effect on pain. Second, it triggers a heightened perception of stress, which acts as an intermediate factor in the causal pathway between poor sleep quality and first-onset TMD pain.

Biopsychosocial influence on shoulder pain: Rationale and protocol for a pre-clinical trial

BACKGROUND

Chronic musculoskeletal pain conditions are a prevalent and disabling problem. Preventing chronic musculoskeletal pain requires multifactorial treatment approaches that address its complex etiology. Prior cohort studies identified a high risk subgroup comprised of variation in COMT genotype and pain catastrophizing. This subgroup had increased chance of heightened pain responses (in a pre-clinical model) and higher 12month post-operatives pain intensity ratings (in a clinical model). This pre-clinical trial will test mechanisms and efficacy of personalized pain interventions matched to the genetic and psychological characteristics of the high-risk subgroup.

METHODS

Potential participants will be screened for high risk subgroup membership, appropriateness for exercise-induced muscle injury protocol, and appropriateness for propranolol administration. Eligible participants that consent to the study will then be randomized into one of four treatment groups; 1) personalized pharmaceutical and psychological education; 2) personalized pharmaceutical and general education; 3) placebo pharmaceutical and psychological education; 4) placebo pharmaceutical and psychological education. Over the 5-day study period participants will complete an exercise-induced muscle injury protocol and receive study interventions. Pain and disability assessments will be completed daily, with primary outcomes being duration of shoulder pain (number of days until recovery), peak shoulder pain intensity, and peak shoulder disability. Secondary outcomes include inflammatory markers, psychological mediators, and measures of pain sensitivity regulation.

CONCLUSION

This pre-clinical trial builds on prior cohort studies and its completion will provide foundational data supporting efficacy and mechanisms of personalized interventions for individuals that may be at increased risk for developing chronic shoulder pain.

TRIAL REGISTRATION

ClinicalTrials.gov registry, NCT02620579 (Registered on November 13, 2015).