Mechanical Temporal Summation Research Articles

Associations of pain sensitivity and conditioned pain modulation with physical activity: findings from the Multicenter Osteoarthritis Study (MOST)

ObjectiveIndividuals with chronic pain due to knee osteoarthritis (OA) are insufficiently physically active, and alterations of facilitatory and inhibitory nociceptive signaling are common in this population. Our objective was to examine the association of these alterations in nociceptive signaling with objective accelerometer-based measures of physical activity in a large observational cohort. DesignWe used data from the Multicenter Osteoarthritis Study (MOST). Measures of peripheral and central pain sensitivity included pressure pain threshold (PPT) at the knee and mechanical temporal summation (TS) at the wrist, respectively. The presence of descending pain inhibition was assessed by conditioned pain modulation (CPM). Physical activity was quantitatively assessed over 7-days using a lower back-worn activity monitor. Summary metrics included steps/day, activity intensity, and sedentary time. Linear regression analyses were used to evaluate the association of pain sensitivity and the presence of descending pain inhibition with physical activity measures. ResultsData from 1,873 participants was analyzed (55.9% female, age = 62.8±10.0 years). People having greater peripheral and central sensitivity showed lower step counts. CPM was not significantly related to any of the physical activity measures, and none of the exposures were significantly related to sedentary time. ConclusionsIn this cohort, greater peripheral and central sensitivity were associated with reduced levels of objectively-assessed daily step counts. Further research may investigate ways to modify or treat heightened pain sensitivity as a means to increase physical activity in older adults with knee OA.

Preliminary Characterization of Age and Chronic Low Back Pain Effects on Multimodal Pain Sensitivity: A Comparison Study in Older Adults with and Without Chronic Low Back Pain

Though pain sensitivity impairments contribute to chronic pain in younger adults, it is unclear if pain hypersensitivity manifests with aging and is heightened in the geriatric chronic low back pain population. The cross-sectional study preliminarily addressed this gap by measuring pain sensitivity in older adults with chronic low back pain (n = 25) as well as pain-free sex-matched older (n = 25) and younger adults (n = 25). Pain sensitivity was quantified by 8 distinct measures that were subdivided as static (ie, pressure pain thresholds, heat pain thresholds, fixed mechanical pain, and fixed cold pain) and dynamic pain sensitivity (ie, mechanical temporal summation, thermal ramp and hold, heat pain aftersensations, and conditioned pain modulation). Test-retest reliability values for pain sensitivity ranged from moderate to excellent (intraclass correlation coefficients ≥ .500; p’s < .05). The main effect for the group was significant (partial η2 = .413, P < .001), revealing between-group differences in pain sensitivity on 5 out of 8 tests (p’s ≤ .043). Predominantly, both older adult groups demonstrated increased pain facilitation and decreased pain inhibition during dynamic pain sensitivity testing compared to pain-free younger adults (p’s ≤ .044). Despite qualitative differences, static and dynamic pain sensitivity responses were statistically similar between older adults with and without chronic LBP (p’s > .05). Findings suggest pain sensitivity can be reliably measured in older adults and that pain hypersensitivity develops with chronological aging, providing partial support for the theory that pain hypersensitivity may impact geriatric chronic pain populations. Further study is needed to more definitively parse out whether pain hypersensitivity is comparatively heightened in older adults with chronic LBP beyond the influence of chronological aging. PerspectiveThis article establishes that surrogate measures of centrally mediated pain sensitization are heightened with aging. Impaired endogenous pain modulation may influence chronic pain development, maintenance, treatment efficacy, and/or ensuing disability, necessitating research to comprehensively characterize how pain hypersensitivity contributes to geriatric chronic pain conditions.

Investigating Factors Associated with the Development of Postnatal Depression After Cesarean Delivery: A Validation Cohort Study.

This study aimed to validate a proposed association model previously published to determine the clinical relevance of pre-operative determinants in the development of PND after Cesarean delivery (CD). Parturients undergoing elective CD under neuraxial anesthesia were recruited for a prospective cohort study between Oct 2021 and Oct 2022 at KK Women's and Children's Hospital, Singapore. Predelivery pain, psychological and mechanical temporal summation, and demographic data were recorded. A follow-up survey was conducted at 6 to 10 weeks after CD. The primary outcome was the incidence of PND, defined as an Edinburgh Postnatal Depression Scale (EPDS) score ≥ 10. A total of 180 patients were recruited for validation. PND 6 to 10 weeks post-delivery occurred in 18.9% of recruited parturients. Multivariate regression analyses showed that higher pre-operative CSI scores (p=0.0156), higher anxiety levels about upcoming surgery (p=0.0429), increased pre-operative pain scores on movement (p=0.0110), and higher pre-operative HADS subscale scores on anxiety (p=0.0041) were independently associated with the development of PND weeks post-CD. Lower anticipation of pain medication needs (p=0.0038) was independently associated with the development of PND post-CD. The area under curve (AUC) of this multivariable model (training cohort), internal cross validation (training cohort) and external cross validation (validation cohort) were 0.818 (95% CI, 0.746 to 0.889), 0.785 (95% CI, 0.707 to 0.864) and 0.604 (95% CI, 0.497 to 0.710) respectively. The proposed model performed well in a local population. Further refinement is necessary to test the proposed model in populations with social and cultural differences.

The association between mechanical temporal summation, state anxiety at baseline, and persistent low back pain: a 12-month prospective cohort study

BackgroundPersons with acute low back pain (LBP) have a good prognosis for regaining function, while pain often persists. Neurobiological and psychosocial factors are recognized to amplify pain responses, as reported for central sensitization. This study investigated the combination of mechanical temporal summation (TS) chosen to characterize central sensitization and state anxiety representing a psychological factor and their association with persistent pain.MethodsA longitudinal prospective cohort study including 176 participants aged between 18 and 65 with acute LBP was performed. The following independent variables were analyzed at baseline: The mechanical TS at the lower back, of whom the Wind-up ratio (WUR) was calculated, and the state anxiety level measured with the State and Trait Anxiety Inventory (STAI-S). The outcome pain intensity was assessed at baseline and 2,3,6 and 12 months after the onset of acute LBP with the Numeric Rating Scale 0–10 (NRS). Linear mixed models (LMM) were used to analyze the association of the independent variables with pain intensity over time.ResultsThe mean baseline WUR was 1.3 (SD 0.6) for the right and 1.5 (SD 1.0) for the left side. STAI-S revealed a mean score of 43.1 (SD 5.2). Pain intensity was, on average, 5.4 points (SD 1.6) on the NRS and decreased over one year to a mean of 2.2 (SD 2.4). After one year, 56% of the participants still experienced pain. The LMM revealed a considerable variation, as seen in large confidence intervals. Therefore, associations of the independent variables (WUR and STAI-S) with the course of the outcome pain intensity over one year were not established.ConclusionThis investigation did not reveal an association of mechanical TS and state anxiety at baseline with pain intensity during the one-year measurement period. Pain persistence, mediated by central sensitization, is a complex mechanism that single mechanical TS and state anxiety cannot capture.

Association of mechanical temporal summation of pain with muscle co-contraction during walking in people with knee osteoarthritis

BackgroundPeople with knee osteoarthritis walk with excessive muscle co-contraction that can accelerate disease progression. Central pain sensitization is common in people with knee osteoarthritis and may be related to walking patterns. The objective of this study was to examine the relation of central pain sensitization with muscle co-contraction during walking in people with knee osteoarthritis. MethodsThis study reports secondary analysis from baseline data of two clinical trials (n = 90 participants with knee osteoarthritis). The presence of central pain sensitization was measured by mechanical temporal summation at the patella and the wrist. Quadriceps and hamstrings activation was assessed using surface electromyography during walking at self-selected and fast paces. Muscle co-contraction indices for vastus medialis-medial hamstrings and vastus lateralis-lateral hamstrings muscle pairs were calculated during stance phases. Co-contraction outcomes were compared between people with and without mechanical temporal summation at each site, adjusting for age, sex, and body mass index. FindingsPeople with mechanical temporal summation at the knee had greater vastus lateralis-lateral hamstrings co-contraction while walking at a fast pace (P = 0.04). None of the other differences was statistically significant, but the overall trends and effect sizes indicated greater co-contraction in people with temporal summation at the knee irrespective of gait phase, walking speed, or muscle pairs. InterpretationCentral pain sensitization, assessed as mechanical temporal summation at the knee, is related to greater knee muscle co-contraction during fast walking in people with knee osteoarthritis. Thus, mitigating central sensitization may be an interventional target to reduce muscle co-contraction for people with knee osteoarthritis.

Initial effect of high-volume mobilisation with movement on shoulder range of motion and pain in patients with rotator cuff-related shoulder pain: protocol for a randomised controlled trial (Evolution Trial)

IntroductionMobilisation with movement (MWM) is commonly used for treating patients with rotator cuff-related shoulder pain (RCRSP). However, the evidence supporting MWM efficacy for improving shoulder range of motion (ROM) and...

Within-Session Test-Retest Reliability of Pressure Pain Threshold and Mechanical Temporal Summation in Chronic Low Back Pain.

To determine the absolute and relative within-session test-retest reliability of pressure pain threshold (PPT) and temporal summation of pain (TSP) at the low back and the forearm in individuals with chronic low back pain (CLBP) and to test the impact of different sequences of measurements on reliability metrics. Twenty-eight adults with CLBP were recruited. Relative (intraclass correlation coefficient [ICC] and coefficient of variation) and absolute reliability (standard error of measurement and minimal detectable changes) were quantified at 4 sites (back: sacrum and lumbar erector spinae; wrist: hand dorsum and wrist flexors) for PPT and 2 sites (hand and low back) for TSP, for various sequences of measurements. Systematic differences were found between within test and retest for most PPT sequences at the lumbar erector spinae site and 1 TSP sequence (1-2-3) at back and hand sites, precluding reliability analyses for these data. Within-session PPT relative reliability was excellent at low back (ICC = 0.83 to 0.94) and wrist (ICC = 0.88 to 0.97) sites, whereas TSP showed good to excellent reliability at hand (ICC = 0.80 to 0.90) and low back (ICC = 0.73 to 0.89). In general, 2 and 3 measurements optimized absolute and relative reliability for TSP and PPT, respectively. Within-session reliability was generally excellent for PPT and TSP at the low back and hand sites among individuals with CLBP. We recommend using 3 measurements for PPT and 2 for TSP to optimize reliability. Caution is recommended when testing PPT of the painful lower back area since a systematic difference was present between the test and retest.

Risk factors for persistent pain after breast cancer surgery: a multicentre prospective cohort study.

Identifying factors associated with persistent pain after breast cancer surgery may facilitate risk stratification and individualised management. Single-population studies have limited generalisability as socio-economic and genetic factors contribute to persistent pain development. Therefore, this prospective multicentre cohort study aimed to develop a predictive model from a sample of Asian and American women. We enrolled women undergoing elective breast cancer surgery at KK Women's and Children's Hospital and Duke University Medical Center. Pre-operative patient and clinical characteristics and EQ-5D-3L health status were recorded. Pain catastrophising scale; central sensitisation inventory; coping strategies questionnaire-revised; brief symptom inventory-18; perceived stress scale; mechanical temporal summation; and pressure-pain threshold assessments were performed. Persistent pain was defined as pain score ≥ 3 or pain affecting activities of daily living 4months after surgery. Univariate associations were generated using generalised estimating equations. Enrolment site was forced into the multivariable model, and risk factors with p < 0.2 in univariate analyses were considered for backwards selection. Of 210 patients, 135 (64.3%) developed persistent pain. The multivariable model attained AUC=0.807, with five independent associations: age (OR 0.85 95%CI 0.74-0.98 per 5 years); diabetes (OR 4.68, 95%CI 1.03-21.22); pre-operative pain score at sites other than the breast (OR 1.48, 95%CI 1.11-1.96); previous mastitis (OR 4.90, 95%CI 1.31-18.34); and perceived stress scale (OR 1.35, 95%CI 1.01-1.80 per 5 points), after adjusting for: enrolment site; pre-operative pain score at the breast; pre-operative overall pain score at rest; postoperative non-steroidal anti-inflammatory drug use; and pain catastrophising scale. Future research should validate this model and evaluate pre-emptive interventions to reduce persistent pain risk.

Sensitivity to movement-evoked pain, central sensitivity symptoms, and pro-nociceptive profiles in people with chronic shoulder pain: Aparallel-group cross-sectional investigation.

To investigate whether sensitivity to movement-evoked pain (SMEP), central sensitivity symptom burden, and quantitative sensory testing (QST) outcomes differ between healthy controls and people with chronic shoulder pain. People with chronic shoulder pain (n=39) and healthy controls (n=26) completed validated questionnaires measuring demographic, pain characteristics, psychological factors, social support, sleep quality, central sensitivity inventory (CSI), and physical activity levels. A blinded assessor administered QST measuring pressure pain threshold, temporal summation, conditioned pain modulation, and cold hyperalgesia. All participants performed repeated lifting of weighted canisters and reported severity of pain over successive lifts of the weighted canisters. Between-group differences in the QST, SMEP and CSI scores were investigated. Demographic and psychosocial variables were adjusted in the analyses. Dynamic mechanical allodynia, mechanical temporal summation, movement-evoked pain scores, SMEP index, and CSI scores were significantly (p ≤ 0.05) higher in the chronic shoulder pain group than in healthy controls. A significant proportion of people with chronic shoulder pain presented with pro-nociceptive profiles and experienced higher pain severity, interference, and disability. People with chronic shoulder pain displayed symptoms and signs of central sensitization. Future research should investigate the predictive role of central sensitization on clinical outcomes in shoulder pain.

Experimental Pain Phenotype Profiles in Community-dwelling Older Adults.

Pain sensitivity and the brain structure are critical in modulating pain and may contribute to the maintenance of pain in older adults. However, a paucity of evidence exists investigating the link between pain sensitivity and brain morphometry in older adults. The purpose of the study was to identify pain sensitivity profiles in healthy, community-dwelling older adults using a multimodal quantitative sensory testing protocol and to differentiate profiles based on brain morphometry. This study was a secondary analysis of the Neuromodulatory Examination of Pain and Mobility Across the Lifespan (NEPAL) study. Participants completed demographic and psychological questionnaires, quantitative sensory testing, and a neuroimaging session. A Principal Component Analysis with Varimax rotation followed by hierarchical cluster analysis identified 4 pain sensitivity clusters (the "pain clusters"). Sixty-two older adults ranging from 60 to 94 years old without a specific pain condition (mean [SD] age=71.44 [6.69] y, 66.1% female) were analyzed. Four pain clusters were identified characterized by (1) thermal pain insensitivity; (2) high pinprick pain ratings and pressure pain insensitivity; (3) high thermal pain ratings and high temporal summation; and (4) thermal pain sensitivity, low thermal pain ratings, and low mechanical temporal summation. Sex differences were observed between pain clusters. Pain clusters 2 and 4 were distinguished by differences in the brain cortical volume in the parieto-occipital region. While sufficient evidence exists demonstrating pain sensitivity profiles in younger individuals and in those with chronic pain conditions, the finding that subgroups of experimental pain sensitivity also exist in healthy older adults is novel. Identifying these factors in older adults may help differentiate the underlying mechanisms contributing to pain and aging.

Evidence for alterations to dynamic quantitative sensory tests in patients with chronic temporomandibular myalgia: A systematic review of observational studies with meta-analysis.

Conflicting results exist between somatosensory profiles of patients with temporomandibular myalgia (TMDm). The objective of this review was to examine whether adults with TMDm show altered responses to dynamic quantitative sensory tests compared with healthy controls. We searched five electronic databases for studies, excluding those without suitable controls or where TMDm was associated with confounding non-musculoskeletal disorders. Risk of bias was assessed with the SIGN case-control study checklist. Findings were structured around dynamic quantitative sensory tests and their localization. Where possible, we performed meta-analysis with a random inverse variance model to compare patients with TMDm and healthy controls. Statistical heterogeneity was estimated with Chi² test and inconsistency index, I². We extracted data from 23 studies comprising 1284 adults with chronic TMDm and 2791 healthy controls. Risk of bias was assessed as high for 20 studies. Mechanical temporal summation, the most studied phenomenon (14studies), is increased in the upper limb of patients with TMDm (SMD=0.43; 95% CI: .11 to .75; p=.009) but not in the jaw area (p=.09) or in the cervical area (p=.29). Very little evidence for altered thermal temporal summation (five studies), conditioned pain modulation (seven studies), exercise-induced hypoalgesia (two studies), placebo analgesia (two studies), stress-induced hypoalgesia (one study) and offset analgesia (one study) was found. A major limitation of this review was the risk of bias of included studies. Future studies would benefit from following methodological guidelines and consideration of confounding factors.

Evaluation of intraoperative ketamine on the prevention of severe rebound pain upon cessation of peripheral nerve block: a prospective randomised, double-blind, placebo-controlled study

BackgroundPain after resolution of peripheral nerve block, known as ‘rebound pain’ (RP), is a major problem in outpatient surgery. The primary objective was to evaluate the benefit of intraoperative ketamine at an anti-hyperalgesic dose on the incidence of rebound pain after upper limb surgery under axillary plexus block in ambulatory patients. The secondary objective was to better understand the rebound pain phenomenon (individual risk factors). MethodsIn this prospective, double-blind study, patients were randomised to receive either a single dose of i.v. ketamine (0.3 mg kg−1) or a placebo. Preoperative mechanical temporal summation and central sensitization inventory were applied to question underlying central sensitisation. Pain catastrophising and Douleur Neuropathique 4 questionnaires were used. Rebound pain was defined as pain intensity score >7 (numeric rating scale, 0–10) after block resolution. Postoperative pain was recorded at Days 1, 4, and 30 after discharge. ResultsA total of 109 subjects completed the study, and 40.4% presented with rebound pain. Ketamine administration did not reduce rebound pain incidence or intensity. Temporal summation and central sensitisation inventory scores did not differ between subjects with and without rebound pain. The predictive risk factors were bone surgery (odds ratio [OR]=5.2; confidence interval [CI], 1.9–14.6), severe preoperative pain (OR=4.2; CI, 1.5–11.7), and high pain catastrophising (OR=4.8; CI, 1.0–22.3). At Day 30, the average daily pain was higher in the rebound pain group involving neuropathic characteristics. ConclusionKetamine at an anti-hyperalgesic dose showed no benefit on rebound pain development. Although central sensitisation might not be involved, preoperative pain intensity, and catastrophising stand as risk factors. Because rebound pain remains frequent despite adequate procedure-specific postoperative analgesia, future studies should focus on patient-specific pain management.

Does weight-bearing versus non-weight-bearing pain reflect different pain mechanisms in knee osteoarthritis?: the Multicenter Osteoarthritis Study (MOST)

Knee osteoarthritis (OA) is predominantly characterized by pain with weight-bearing activities. Pain at rest also occurs but the mechanisms for this are not clear. We evaluated the relations of nociceptive signal alterations to weight-bearing and non-weight-bearing pain in knee OA. We used data from a NIH-funded longitudinal cohort of older adults with or at risk of knee OA. We evaluated quantitative sensory testing (QST) measures (pressure pain threshold (PPT) at patellae and the wrist; mechanical temporal summation (TS); conditioned pain modulation (CPM)). Each WOMAC pain question was dichotomized as having at least moderate pain, and we further categorized them as weight-bearing pain and non-weight-bearing pain. We evaluated the relation of QST measures to each pain outcome using logistic regression, adjusting for potential confounders. 2,749 participants (5,479 knees) were included (mean age 64±11, 57% female). Each SD unit decrease in patellar PPT was associated with greater odds of both weight-bearing pain (OR 1.51 (95% CI 1.27, 1.79)) and non-weight-bearing pain (OR 1.46 (1.20-1.77)), while wrist PPT was associated with greater odds of weight-bearing pain (OR 1.27 (1.15, 1.39)) but only with pain during sitting/lying (OR 1.20 (1.01, 1.43)). TS was significantly associated with greater odds of pain with walking and stairs (OR 1.11 (1.01, 1.23), 1.11 (1.03, 1.20), respectively). CPM was not associated with any pain outcomes. Our findings challenge the hypothesis that non-weight-bearing pain may reflect greater pain sensitization and/or inefficient CPM than weight-bearing pain in knee OA, suggesting other mechanisms are likely responsible.

Predicting pain after Cesarean delivery: pressure algometry, temporal summation, three-item questionnaire

Approximately one in five women will experience severe postoperative pain after Cesarean delivery (CD). Previously, a bedside three-item questionnaire (3-IQ) has shown to predict women experiencing higher evoked pain intensity after CD, with an area under the receiver operator characteristics (ROC) curve of 0.72. We hypothesized that the addition of psychophysical pain tests to the existing 3-IQ would improve the ability to predict severe pain in women undergoing elective CD under spinal anesthesia METHODS: This was a prospective cohort study on women undergoing elective CD under spinal anesthesia. Women were assessed preoperatively using the 3-IQ, pressure algometry (PA) and mechanical temporal summation (TS) response. All women received standard perioperative care, including a multimodal analgesia regimen that included intrathecal fentanyl and morphine. A 0-100 mm visual analogue scale (VAS) was used to assess the severity of pain at rest (VASr) and on movement (VASm) at 24 and 48 hr after surgery. Patient satisfaction and opioid consumption were also recorded. We performed ROC curve analyses to assess whether we could improve the ability to predict our primary outcome of severe pain on movement at 24 hr (VASm24 ≥ 70). We studied 195 women. Median [interquartile range] VASm24 was 53 [32-72] and 28% of patients experienced a VASm24 ≥ 70. The ability to predict a VASm24 ≥ 70 assessed by the area under the ROC curve was 0.64 using the 3-IQ and 0.67 using the 3-IQ combined with TS and PA. The addition of PA and TS to the 3-IQ model resulted in a predictive model that performed similarly to the 3-IQ model alone. Further research is warranted in this area to better predict women at risk of severe pain post CD.

Pro-nociceptive pain modulation profile in patients with acute and chronic shoulder pain: a hypothesis-generating topical review

Shoulder pain is a common musculoskeletal complaint associated with a significant impact on health and socioeconomic outcomes. Current evidence indicates a poor understanding of the mechanisms driving shoulder pain experience. The heightened nociceptive processing (pro-nociceptive pain modulation profile) within the central nervous system could explain variability in the shoulder pain experience. This topical review and hypothesis-generating paper discuss the current evidence and gaps regarding abnormal nociceptive processing in patients with shoulder pain. This paper also proposes hypotheses to test the presence of a pro-nociceptive pain modulation profile by measuring the pain responses to conditioned pain modulation, mechanical temporal summation and movement-evoked pain procedures. Moreover, this paper proposes whether a pro-nociceptive pain modulation profile can explain the variability in the pain experience in people with shoulder pain. Gaining insights into the abnormal nociceptive processing in people with acute and chronic shoulder pain will guide future research and clinical practice to improve shoulder pain outcomes.

Mechanical temporal summation is associated with greater muscle co-contraction during walking in knee osteoarthritis

Purpose: People with knee osteoarthritis (OA) walk with altered motor patterns, including excessive muscular co-contraction, that can lead to disease worsening. Factors related to increased muscular co-contraction during walking in people with knee OA are not well known, but one is suggested to be pain sensitization. An abnormally augmented pain response to repetitive mechanical stimuli can be present in people with chronic pain. Mechanical loading during activities like walking could activate peripheral and central nociceptive pathways ; if the central nervous system is sensitized, it is possible that could then affect motor function leading to altered muscle activity.

Within-session test-retest reliability of pressure pain threshold and mechanical temporal summation in healthy subjects

To determine the absolute and relative intra-rater within-session test-retest reliability of pressure pain threshold (PPT) and mechanical temporal summation of pain (TSP) at the low back and the forearm in healthy participants and to test the influence of the number and sequence of measurements on reliability metrics. In 24 participants, three PPT and TSP measures were assessed at four sites (2 at the low back, 2 at the forearm) in two blocks of measurements separated by 20 minutes. The standard error of measurement, the minimal detectable change (MDC) and the intraclass correlation coefficient (ICC) were investigated for five different sequences of measurements (e.g. measurement 1, 1-2, 1-2-3). The MDC for the group (MDCgr) for PPT ranged from 28.71 to 50.56 kPa across the sites tested, whereas MDCgr for TSP varied from 0.33 to 0.57 out of 10 (numeric scale). Almost all ICC showed an excellent relative reliability (between 0.80 and 0.97), except when only the first measurement was considered (moderate). Although minimal differences in absolute PPT reliability were present between the different sequences, in general, using only the first measurement increase measurement error. Three TSP measures reduced the measurement error. We established that two measurements of PPT and three of TSP reduced the measurement error and demonstrated an excellent relative reliability. Our results could be used in future pain research to confirm the presence of true hypo/hyperalgesia for paradigms such as conditioned pain modulation or exercise-induced hypoalgesia, indicated by a change exceeding the measurement variability.

Pain relief for osteoarthritis through combined treatment (PROACT): Protocol for a randomized controlled trial of mindfulness meditation combined with transcranial direct current stimulation in non-Hispanic black and white adults with knee osteoarthritis

Knee osteoarthritis (OA) is a leading cause of late life pain and disability, and non-Hispanic black (NHB) adults experience greater OA-related pain and disability than non-Hispanic whites (NHWs). Recent evidence implicates psychosocial stress, cognitive-attentional processes, and altered central pain processing as contributors to greater OA-related pain and disability among NHBs. To address these ethnic/race disparities, this clinical trial will test whether a mindfulness intervention (Breathing and Attention Training, BAT) combined with transcranial direct current stimulation (tDCS) will enhance pain modulatory balance and pain-related brain function, reduce clinical pain, and attenuate ethnic differences therein, among NHBs and NHWs with knee OA. Participants will complete assessments of clinical pain, function, psychosocial measures, and quantitative sensory testing (QST), including mechanical temporal summation and conditioned pain modulation. Neuroimaging will be performed to examine pain-related brain structure and function. Then, participants will be randomized to one of four groups created by crossing two BAT conditions (Real vs. Sham) with two tDCS conditions (Real vs. Sham). Participants will then undergo five treatment sessions during which the assigned BAT and tDCS interventions will be delivered concurrently for 20 min over one week. After the fifth intervention session, participants will undergo assessments of clinical pain and function, QST and neuroimaging identical to the pretreatment measures, and monthly follow-up assessments of pain will be conducted for three months. This will be the first study to determine whether mindfulness and tDCS treatments will show additive or synergistic effects when combined, and whether treatment effects differ across ethnic/race groups.

Greater mechanical temporal summation of pain in Latinx-Americans and the role of adverse life experiences.

Adverse life experiences disproportionately impact Latinx-Americans and are related to greater chronic pain rates. However, little is known about how adversities interact with central pain mechanisms for the development of later pain among Latinx-Americans. The current study examined the relationship between adverse life experiences (eg, trauma and ethnic discrimination) and correlates (eg, social status) with mechanical temporal summation of pain (a proxy measure of central sensitization) between pain-free U.S. native Latinx (n = 65) and non-Hispanic White (NHW) (n = 51) adults. Participants completed self-report adverse life experience and correlational measures regarding childhood and adulthood and a mechanical temporal summation protocol. Relative to NHWs, Latinx-Americans reported experiencing significantly greater trauma, discrimination, and lower social status during childhood and adulthood, along with greater temporal summation. Contrary to hypotheses, recent and lifetime experiences of ethnic discrimination significantly correlated with less temporal summation among Latinx-Americans. Decreases in objective and subjective social status across the lifespan (childhood to present day) correlated with greater temporal summation for Latinx-Americans. However, r-to-z transformation analyses confirmed that significant adversity and social status correlations observed among the Latinx group did not significantly differ from NHW participants. The present findings highlight the complex association between adverse experiences, adverse experience risk factors, and pain for Latinx-Americans. Given the disproportion of experienced pain and adversity among Latinx-Americans, the current findings suggest that a better understanding of the unique adversities for this sample may help elucidate the mechanisms underlying the relationship between adversities, adversity correlates, and pain risk for Latinx-Americans.

Risk Factors Associated with Development of Acute and Sub-Acute Post-Cesarean Pain: A Prospective Cohort Study.

BackgroundAlthough cesarean delivery is one of the most commonly performed surgical procedures, robust data regarding post-cesarean pain is still lacking. Recent studies showed an association between pain upon local anesthetic (LA) injection for spinal anesthesia, or the use of a “three simple questions”, and acute post-cesarean pain. Nevertheless, these assessments have yet to be validated further, despite their relative ease of use. We aimed to assess the association between pain score upon LA injection with acute post-cesarean pain after 24 hours at rest (primary outcome) and sub-acute post-cesarean pain lasting for 4 weeks or more (secondary outcome).MethodsWomen undergoing cesarean delivery under spinal anesthesia were given pre-operative questionnaires on pain and psychological vulnerability. We also assessed the pain score upon LA injection and mechanical temporal summation. Univariate and multivariable logistic regressions were performed.ResultsThe incidence of moderate-to-severe acute post-cesarean pain at 24 hours was 21.0% (95% CI=16.6–27.6%) (48 of 217 patients). Pain score upon LA injection was not significantly associated with acute post-cesarean pain after 24 hours at rest (unadjusted OR=1.10, 95% CI=0.95–1.27, P=0.21). However, pain score upon LA injection was significantly associated with sub-acute post-cesarean pain (adjusted OR=1.29, 95% CI=1.07–1.55, P=0.0089) with significant covariate of increased pre-operative central sensitization inventory (CSI) scores (adjusted OR=1.05, 95% CI=1.01–1.09, P=0.0111; area under the curve (AUC)=0.691).ConclusionThere was no association between increased pain score upon LA injection and acute post-cesarean pain, but it was associated with sub-acute post-cesarean pain. Further work is needed to define pain score upon LA injection as a convenient pragmatic measure of risk stratifying patients predisposed to sub-acute post-cesarean pain.