Differences in Clinical Pain and Experimental Pain Sensitivity Between Asian Americans and Whites With Knee Osteoarthritis

OBJECTIVE

Ethnicity has been associated with clinical and experimental pain responses. Whereas ethnic disparities in pain in other minority groups compared with whites are well described, pain in Asian Americans remains poorly understood. The purpose of this study was to characterize differences in clinical pain intensity and experimental pain sensitivity among older Asian American and non-Hispanic white (NHW) participants with knee osteoarthritis (OA).

METHODS

Data were collected from 50 Asian Americans ages 45 to 85 (28 Korean, 9 Chinese, 7 Japanese, 5 Filipino, and 1 Indian) and compared with 50 age-matched and sex-matched NHW individuals with symptomatic knee OA pain. The Western Ontario and McMaster Universities Osteoarthritis Index and Graded Chronic Pain Scale were used to assess the intensity of clinical knee pain. In addition, quantitative sensory testing was used to measure experimental sensitivity to heat-induced and mechanically induced pain.

RESULTS

Asian American participants had significantly higher levels of clinical pain intensity than NHW participants with knee OA. In addition, Asian American participants had significantly higher experimental pain sensitivity than NHW participants with knee OA.

DISCUSSION

These findings add to the growing literature regarding ethnic and racial differences in clinical pain intensity and experimental pain sensitivity. Asian Americans in particular may be at risk for clinical pain and heightened experimental pain sensitivity. Further investigation is needed to identify the mechanisms underlying ethnic group differences in pain between Asian Americans and NHWs, and to ensure that ethnic group disparities in pain are ameliorated.

GWAS Identifies New Loci for Painful Temporomandibular Disorder: Hispanic Community Health Study/Study of Latinos

Temporomandibular disorder (TMD) is a musculoskeletal condition characterized by pain and reduced function in the temporomandibular joint and/or associated masticatory musculature. Prevalence in the United States is 5% and twice as high among women as men. We conducted a discovery genome-wide association study (GWAS) of TMD in 10,153 participants (769 cases, 9,384 controls) of the US Hispanic Community Health Study/Study of Latinos (HCHS/SOL). The most promising single-nucleotide polymorphisms (SNPs) were tested in meta-analysis of 4 independent cohorts. One replication cohort was from the United States, and the others were from Germany, Finland, and Brazil, totaling 1,911 TMD cases and 6,903 controls. A locus near the sarcoglycan alpha ( SGCA), rs4794106, was suggestive in the discovery analysis ( P = 2.6 × 10⁶) and replicated (i.e., 1-tailed P = 0.016) in the Brazilian cohort. In the discovery cohort, sex-stratified analysis identified 2 additional genome-wide significant loci in females. One lying upstream of the relaxin/insulin-like family peptide receptor 2 ( RXP2) (chromosome 13, rs60249166, odds ratio [OR] = 0.65, P = 3.6 × 10^-8) was replicated among females in the meta-analysis (1-tailed P = 0.052). The other (chromosome 17, rs1531554, OR = 0.68, P = 2.9 × 10^-8) was replicated among females (1-tailed P = 0.002), as well as replicated in meta-analysis of both sexes (1-tailed P = 0.021). A novel locus at genome-wide level of significance (rs73460075, OR = 0.56, P = 3.8 × 10^-8) in the intron of the dystrophin gene DMD (X chromosome), and a suggestive locus on chromosome 7 (rs73271865, P = 2.9 × 10^-7) upstream of the Sp4 Transcription Factor ( SP4) gene were identified in the discovery cohort, but neither of these was replicated. The SGCA gene encodes SGCA, which is involved in the cellular structure of muscle fibers and, along with DMD, forms part of the dystrophin-glycoprotein complex. Functional annotation suggested that several of these variants reside in loci that regulate processes relevant to TMD pathobiologic processes.

Time to Onset of Sustained Postoperative Pain Relief (SuPPR): Evaluation of a New Systems-level Metric for Acute Pain Management

OBJECTIVES

Prior work on postoperative pain trajectories has examined pain score changes over time using daily averages of pain scores. However, little is known about the time required until patients consistently report minimal postoperative pain.

MATERIALS AND METHODS

We conducted a retrospective cohort study of surgical case data from 7293 adult patients to examine the impact of age, sex, and the type of surgery on the time to sustained postoperative pain relief (SuPPR). We defined SuPPR as the time required until a patient reports the first of multiple (2, 3, 4, or 5 sequential measurements; eg, SuPPR-2, SuPPR-3), uninterrupted, mild pain scores (≤4/10).

RESULTS

Overall, SuPPR times ranged from 3 minutes for SuPPR-2 and 9 minutes for SuPPR-5 to 160.1 hours for SuPPR-2 and 183.1 hours for SuPPR-5. For the SuPPR-2 outcome, the median time to event was 10.9 hours (interquartile range, 3 to 26.1 h) after surgery. For the SuPPR-5 outcomes, the median time to event was 31.5 hours (interquartile range, 17.8 to 54.2 h) after surgery. The peak median difference between 2 sequential SuPPR definitions was between SuPPR-3 and SuPPR-2 at 9 hours, with subsequent decreases to 6.5 hours between SuPPR-4 and SuPPR-3, and 5.2 hours between SuPPR-5 and SuPPR-4. There were statistically different differences across SuPPR-2 through SuPPR-5 definitions by age, sex, and type of surgery.

DISCUSSION

Although additional analyses are necessary, SuPPR may represent a novel method for evaluating acute pain service performance.

The effect of EHR-integrated patient-reported outcomes on satisfaction with chronic pain care

OBJECTIVES

Given its complexity, chronic noncancer pain presents an opportunity to use health information technology (IT) to improve care experiences. The objective of this study was to assess whether integrating patient-reported outcomes (PROs) data in an electronic health record (EHR) affects provider and patient satisfaction with chronic noncancer pain care.

STUDY DESIGN

We conducted a pragmatic cluster randomized trial involving 4 family medicine clinics.

METHODS

We enrolled primary care providers (PCPs) and their patients with chronic noncancer pain. In the first 7 months (education phase), PCPs in intervention practices received education on how to use PROs for pain care. In the second 7 months (PRO phase), patients in intervention practices reported pain-related outcomes on arrival at their visits. PROs were immediately reported to PCPs through the EHR. Control group PCPs provided usual care. We compared intervention and control practices in terms of provider and patient satisfaction with care.

RESULTS

During the education phase, patients' mean ratings of their visits did not differ between control and intervention (9.33 vs 9.08; P = .20). During the PRO phase, patients' mean ratings did not differ between control and intervention (9.28 vs 9.01; P = .20). Similarly, there were no differences between the intervention and control groups in terms of provider satisfaction.

CONCLUSIONS

Delivering EHR-integrated PROs did not consistently improve patient or provider satisfaction. Positively, we found no evidence that the PRO tools negatively affected satisfaction. Future studies and technological innovations are needed to translate point-of-care health IT tools into improvements in patient and provider experiences.

Testing Assumptions in Human Pain Models: Psychophysical Differences Between First and Second Pain

Acute pain arises from activation of myelinated (A delta) and unmyelinated (C) nociceptive afferents, leading to first (A-fiber) or second (C-fiber) pain sensations. The current study sought to investigate first and second pain within glabrous and hairy skin sites in human upper limbs. Fifty healthy adults (25 male/25 female, 18-30 years old, mean = 20.5 ± 1.4 years) participated in a psychophysical study investigating electronically rated, thermal first and second pain sensations within the glabrous skin at the palm and hairy skin of the forearm. Repeated measures analysis of variance indicated that the threshold for first pain was lower (more sensitive) than for second pain (P = .004), for glabrous as well as hairy skin, and thresholds at glabrous skin were higher than for hairy skin (P = .001). Hairy skin presented a steeper slope for testing, whereas there were no differences in slope between first and second pain. The study findings support assumptions associated with mechanistic differences between first and second pain sensations, while offering a novel method for producing first and second pain with the same thermal stimulus. Efforts to understand abnormalities among people with clinical pain and development of new therapeutic agents will benefit from specific psychophysical methods.

PERSPECTIVE

This article presents a novel method for directly comparing first and second pain within the same thermal stimulus. The ability to directly compare first and second pain sensations can aid in understanding pain abnormalities in clinical pain and development of therapeutic aids.

Estrogen-Induced Monocytic Response Correlates with TMD Pain: A Case Control Study

Temporomandibular disorders (TMD) are a set of conditions characterized by pain and dysfunction in the temporomandibular joint and muscles of mastication. These pain conditions are associated with considerable morbidity, societal costs, and reduced quality of life. The prevalence varies between 4% and 10%, with females at higher risk, and a higher prevalence occurs during reproductive years. The increased prevalence of TMD in females and low prevalence in childhood reinforce that sex hormones, like estrogen, play an important, complex role in the pathophysiology of these disorders. The goal of this study was to determine whether women with TMD exhibit a monocytic hyperinflammatory response compared with control women, and to examine associations of monocytic inflammatory responses with clinical pain. Eighteen women, aged 18 to 35 y, were seen during their follicular menstrual phase. A blood sample was collected, a clinical questionnaire about pain history was administered, and a Research Diagnostic Criteria (RDC) exam was performed. Extracted monocytes were stimulated with the toll-like receptor (TLR)-4 ligand, lipopolysaccharide (LPS), in the presence and absence of estrogen, and the levels of IL6 expression evaluated. Women with TMD showed a systemic hyperinflammatory phenotype, manifested by an increased monocytic release of cytokines after an inflammatory insult, and this was further increased by estrogen. In addition, monocytes from participants who self-reported more pain on the VAS scale produced higher levels of IL6 compared with those from participants who self-reported lower pain sensitivity. These data suggest that an estrogen-induced hyperinflammatory phenotype in women with TMD may at least in part contribute to heightened clinical pain, perhaps via central sensitization.

Effects of High-Dose Capsaicin on TMD Subjects: A Randomized Clinical Study

Temporomandibular joint disorder (TMD) is a complex musculoskeletal disorder that presents with pain, limited jaw opening, and abnormal noises in the temporomandibular joint. Despite the significant impact that TMD has in terms of suffering and financial burden, relatively few new treatments have emerged; therefore, development of novel treatments to treat TMD pain remains a high priority. The rationale of this study was to use a double-blind, vehicle-controlled clinical trial to evaluate the effects of a high-concentration (8%) capsaicin cream on TMD. This is based on the hypothesis that targeting TRP vanilloid subfamily member 1 (TRPV1) for pain control may provide a novel method for pain relief in TMD patients. TRPV1 is primarily expressed on a population of nociceptive-specific neurons and provides a candidate target for the development of pain treatments. Capsaicin is the primary agonist for TRPV1 and has been used previously in relatively low doses (0.025% to 0.075%) as a therapeutic for a variety of pain disorders, including postherpetic neuralgia and osteoarthritis; however, analgesic efficacy remains equivocal. TMD and healthy control subjects were assigned to either an active capsaicin or vehicle control group. The treatments were applied for 2 h and then removed. Quantitative sensory testing (QST) was completed prior to drug application (baseline), 2 h after drug application, and 1 wk later. Perceived pain intensity was measured using a visual analog scale (VAS) following capsaicin or vehicle cream application. Significantly lower pain was reported in the week after application in the capsaicin-treated TMD subjects. For QST measures, there was a decreased thermal pain threshold 2 h after capsaicin application for both the control and TMD groups, but this resolved within a week. Capsaicin had no effect on pressure pain threshold or mechanical sensitivity in both TMD and healthy individuals. This study demonstrates that 8% topical capsaicin therapy is a relatively safe, simple, and effective treatment for patients with TMD. Knowledge Transfer Statement: This study evaluated a novel topical capsaicin therapy for reducing orofacial pain. The results of this study can be used to provide another treatment option for patients with TMD.

Biopsychosocial Influence on Shoulder Pain: Influence of Genetic and Psychological Combinations on Twelve-Month Postoperative Pain and Disability Outcomes

OBJECTIVE

To identify novel combinations of genetic and psychological factors that predicted 12-month postoperative pain and disability outcomes following arthroscopic shoulder surgery.

METHODS

A prospective presurgical cohort (n = 150) was recruited to complete validated psychological questionnaires and have their DNA collected from saliva. DNA was genotyped for a priori selected genes involved with pain modulation (ADRB2, OPRM1, AVPR1A, GCH1, and KCNS1) and inflammation (IL1B, TNF/LTA, and IL6). The outcome measures of interest were the Brief Pain Inventory and Disabilities of the Arm, Shoulder, and Hand questionnaire. Followup for the cohort was at 3, 6, and 12 months postoperatively. After controlling for age, sex, race, and preoperative status, genetic and psychological factors were entered as main effects and interaction terms in separate general linear models for predicting postoperative pain and disability outcomes.

RESULTS

Seven interactions involving pain-modulatory genes were identified. Three provided strong statistical evidence for different outcomes, including KCNS1 and kinesiophobia for preoperative pain intensity, ADRB2 and depressive symptoms for postoperative course, and GCH1 and anxiety symptoms for 12-month pain-intensity outcome. Ten interactions involving inflammatory genes were identified. Three provided strong statistical evidence for the 12-month postoperative course outcome, including 2 different IL6 single-nucleotide polymorphism and pain catastrophizing, and IL6 and depressive symptoms.

CONCLUSION

The current study identified novel genetic and psychological interactions that can be used in future studies to further understand the development of persistent postoperative pain and investigate the effectiveness of tailored treatment.

Assessment of Chronic Pain: Domains, Methods, and Mechanisms

Accurate classification of chronic pain conditions requires reliable and valid pain assessment. Moreover, pain assessment serves several additional functions, including documenting the severity of the pain condition, tracking the longitudinal course of pain, and providing mechanistic information. Thorough pain assessment must address multiple domains of pain, including the sensory and affective qualities of pain, temporal dimensions of pain, and the location and bodily distribution of pain. Where possible, pain assessment should also incorporate methods to identify pathophysiological mechanisms underlying the pain. This article discusses assessment of chronic pain, including approaches available for assessing multiple pain domains and for addressing pathophysiological mechanisms. We conclude with recommendations for optimal pain assessment.

PERSPECTIVE

Pain assessment is a critical prerequisite for accurate pain classification. This article describes important features of pain that should be assessed, and discusses methods that can be used to assess the features and identify pathophysiological mechanisms contributing to pain.

Experimental pain phenotyping in community-dwelling individuals with knee osteoarthritis

Pain among individuals with knee osteoarthritis (OA) is associated with significant disability in older adults, and recent evidence demonstrates enhanced experimental pain sensitivity. Although previous research showed considerable heterogeneity in the OA clinical pain presentation, less is known regarding the variability in responses to experimental pain. The present study included individuals with knee OA (n = 292) who participated in the Understanding Pain and Limitations in Osteoarthritic Disease study and completed demographic and psychological questionnaires followed by a multimodal quantitative sensory testing (QST) session. Quantitative sensory testing measures were subjected to variable reduction procedures to derive pain sensitivity index scores, which in turn were entered into a cluster analysis. Five clusters were significantly different across all pain sensitivity index variables (P < 0.001) and were characterized by: (1) low pain sensitivity to pressure pain (N = 39); (2) average pain sensitivity across most modalities (N = 88); (3) high temporal summation of punctate pain (N = 38); (4) high cold pain sensitivity (N = 80); and (5) high sensitivity to heat pain and temporal summation of heat pain (N = 41). Clusters differed significantly by race, gender, somatic reactivity, and catastrophizing (P < 0.05). Our findings support the notion that there are distinct subgroups or phenotypes based on experimental pain sensitivity in community-dwelling older adults with knee OA, expanding previous findings of similar cluster characterizations in healthy adults. Future research is needed to further understand the pathophysiological mechanisms underlying pain within these subgroups, which may be of added value in tailoring effective treatments for people with OA.

Endogenous Opioids, Blood Pressure, and Diffuse Noxious Inhibitory Controls: A Preliminary Study

A 2003 study suggested that there are age differences in diffuse noxious inhibitory controls (DNIC), a form of endogenous pain inhibition. The present report describes a followup study employing a pharmacological blockade of endogenous opioids, i.e., using naloxone, in a small subset ( n = 6) of healthy young volunteers to characterize the opioid-dependence of DNIC, as well as DNIC's association with cardiovascular reactivity. Findings suggested that, while opioid blockade enhanced cardiovascular reactivity to cold pain, DNIC was not affected by administering naloxone. Interestingly, greater cardiovascular responses to noxious cold were associated with enhanced DNIC in this small sample. This relationship, which did not appear opioid-dependent, supports previous models integrating cardiovascular activity with the functioning of pain-modulatory systems.

Enhanced Pain Sensitivity Among Individuals With Symptomatic Knee Osteoarthritis: Potential Sex Differences in Central Sensitization

OBJECTIVE

Symptomatic knee osteoarthritis (OA) is a condition commonly associated with increased pain, disability, and functional limitations. Given the poor correspondence between radiographic evidence and clinical pain, central sensitization has been implicated as a potential mechanism underlying pain facilitation in knee OA. Sex may be a moderator of centrally mediated changes in knee OA pain; however, few studies have systematically assessed this. Therefore, the aim of this study was to examine differences in peripheral and central sensitization in men and women with symptomatic knee OA, as well as to determine whether these differences vary across age (middle age versus older age).

METHODS

Participants (n = 288) between the ages of 45 and 85 years completed a battery of quantitative sensory pain procedures assessing sensitivity to contact heat, cold pressor, mechanical pressure, and punctate stimuli. Differences in temporal summation (TS) were examined, as well as measures of clinical pain and functional performance.

RESULTS

When compared to men, women exhibited greater sensitivity to multiple pain modalities (i.e., lower heat, cold, pressure thresholds/tolerances, greater TS of pain); however, there were no sex differences in clinical pain, with the exception of greater widespread pain observed in women. Although there were select age-related differences in pain sensitivity, sex differences in pain varied minimally across the age cohort.

CONCLUSION

Overall, these findings provide evidence for greater overall sensitivity to experimental pain in women with symptomatic knee OA compared to men, suggesting that enhanced central sensitivity may be an important contributor to pain in this group.

Painful Temporomandibular Disorder: Decade of Discovery from OPPERA Studies

In 2006, the OPPERA project (Orofacial Pain: Prospective Evaluation and Risk Assessment) set out to identify risk factors for development of painful temporomandibular disorder (TMD). A decade later, this review summarizes its key findings. At 4 US study sites, OPPERA recruited and examined 3,258 community-based TMD-free adults assessing genetic and phenotypic measures of biological, psychosocial, clinical, and health status characteristics. During follow-up, 4% of participants per annum developed clinically verified TMD, although that was a "symptom iceberg" when compared with the 19% annual rate of facial pain symptoms. The most influential predictors of clinical TMD were simple checklists of comorbid health conditions and nonpainful orofacial symptoms. Self-reports of jaw parafunction were markedly stronger predictors than corresponding examiner assessments. The strongest psychosocial predictor was frequency of somatic symptoms, although not somatic reactivity. Pressure pain thresholds measured at cranial sites only weakly predicted incident TMD yet were strongly associated with chronic TMD, cross-sectionally, in OPPERA's separate case-control study. The puzzle was resolved in OPPERA's nested case-control study where repeated measures of pressure pain thresholds revealed fluctuation that coincided with TMD's onset, persistence, and recovery but did not predict its incidence. The nested case-control study likewise furnished novel evidence that deteriorating sleep quality predicted TMD incidence. Three hundred genes were investigated, implicating 6 single-nucleotide polymorphisms (SNPs) as risk factors for chronic TMD, while another 6 SNPs were associated with intermediate phenotypes for TMD. One study identified a serotonergic pathway in which multiple SNPs influenced risk of chronic TMD. Two other studies investigating gene-environment interactions found that effects of stress on pain were modified by variation in the gene encoding catechol O-methyltransferase. Lessons learned from OPPERA have verified some implicated risk factors for TMD and refuted others, redirecting our thinking. Now it is time to apply those lessons to studies investigating treatment and prevention of TMD.

Novel method for assessing age-related differences in the temporal summation of pain

Temporal summation (TS) of pain protocols typically involve the delivery of brief repetitive noxious stimuli held at a constant intensity and measuring the consequent increase in the perceived intensity of pain sensations. To date, no studies have examined the effect of a TS protocol on the perceived spatial dimensions of the pain experience and its interaction with age. This study used a new TS protocol that examined changes in the perceived size of the painful area in 22 younger adults and 20 older adults. Four trials of ten brief heat pulses delivered at a constant intensity were administered on the volar forearm. Interpulse intervals (IPIs) were 2.5 seconds or 3.5 seconds. Subjects rated the peak pain intensity (trials 1 and 3) or the size of the painful area (trials 2 and 4) after each pulse on a 0-100 scale. The magnitude of summation was calculated for each trial. Three seconds and 6 seconds after delivering the last heat pulse, the subjects rated the intensity or the size of any remaining pain (aftersensations). The results indicated that older adults compared to younger adults exhibited significantly greater summation of size ratings for the 2.5-second and 3.5-second IPI trials and size of pain aftersensations at 3 seconds following the 2.5-second IPI TS trial. These results suggest that aging is associated with enhanced endogenous facilitation of the perceived size of pain. The potential clinical and mechanistic implications of enhanced TS of size of pain remain unknown and warrant further investigation.

Exploring Ethnic Differences in Taste Perception

It is well known that nutritional intake can vary substantially as a function of demographic variables such as ethnicity and/or sex. Although a variety of factors are known to underlie the relationship between these demographic variables and nutritional intake, it is interesting to speculate that variation in food intake associated with ethnicity or sex may result, in part, from differences in the perceived taste of foods in these different populations. Thus, we initiated a study to evaluate taste responsiveness in different ethnic groups. Moreover, because of the known differences in taste responsiveness between males and females, analyses were stratified by sex. The ethnic groups tested differed significantly from one another in reported perceived taste intensity. Our results showed that Hispanics and African Americans rated taste sensations higher than non-Hispanic Whites and that these differences were more pronounced in males. Understanding the nature of these differences in taste perception is important, because taste perception may contribute to dietary health risk. When attempting to modify diet, individuals of different ethnicities may require personalized interventions that take into account the different sensory experience that these individuals may have when consuming foods.

Increasing Neuroplasticity to Bolster Chronic Pain Treatment: A Role for Intermittent Fasting and Glucose Administration?

Neuroplastic changes in brain structure and function are not only a consequence of chronic pain but are involved in the maintenance of pain symptoms. Thus, promotion of adaptive, treatment-responsive neuroplasticity represents a promising clinical target. Emerging evidence about the human brain's response to an array of behavioral and environmental interventions may assist in identifying targets to facilitate increased neurobiological receptivity, promoting healthy neuroplastic changes. Specifically, strategies to maximize neuroplastic responsiveness to chronic pain treatment could enhance treatment gains by optimization of learning and positive central nervous system adaptation. Periods of heightened plasticity have been traditionally identified with the early years of development. More recent research, however, has identified a wide spectrum of methods that can be used to "reopen" and enhance plasticity and learning in adults. In addition to transcranial direct current stimulation and transcranial magnetic stimulation, behavioral and pharmacological interventions have been investigated. Intermittent fasting and glucose administration are two propitious strategies, that are noninvasive, inexpensive to administer, implementable in numerous settings, and might be applicable across differing chronic pain treatments. Key findings and neurophysiological mechanisms are summarized, and evidence for the potential clinical contributions of these two strategies toward ameliorating chronic pain is presented.

PERSPECTIVE

Neuroplastic changes are a defining feature of chronic pain and a complicating factor in treatment. Noninvasive strategies to optimize the brain's response to treatment interventions might improve learning and memory, increase the positive adaptability of the central nervous system, and enhance treatment outcomes.

Dental opioid prescribing practices and risk mitigation strategy implementation: Identification of potential targets for provider-level intervention

BACKGROUND

Given the regular use of immediate-release opioids for dental pain management, as well as documented opioid misuse among dental patients, the dental visit may provide a viable point of intervention to screen, identify, and educate patients regarding the risks associated with prescription opioid misuse and diversion. The aims of this statewide survey of dental practitioners were to assess (a) awareness of the scope of prescription opioid misuse and diversion; (b) current opioid prescribing practices; (c) use of and opinions regarding risk mitigation strategies; and (d) use and perceived utility of drug monitoring programs.

METHODS

This cross-sectional study surveyed dentists (N = 87) participating in statewide professional and alumni organizations. Dentists were invited via e-mail and listserv announcement to participate in a one-time, online, 59-item, self-administered survey.

RESULTS

A majority of respondents reported prescribing opioids (n = 66; 75.8%). A minority of respondents (n = 38; 44%) reported regularly screening for current prescription drug abuse. Dentists reported low rates of requesting prior medical records (n = 5; 5.8%). Only 38% (n = 33) of respondents had ever accessed a prescription drug monitoring program (PDMP), and only 4 (4.7%) consistently used a PDMP. Dentists reporting prior training in drug diversion were significantly more likely to have accessed their PDMP, P < .01. Interest in continuing education regarding assessment of prescription drug abuse/diversion and use of drug monitoring programs was high.

CONCLUSIONS

Although most dentists received training related to prescribing opioids, findings identified a gap in existing dental training in the assessment/identification of prescription opioid misuse and diversion. Findings also identified gaps in the implementation of recommended risk mitigation strategies, including screening for prescription drug abuse, consistent provision of patient education, and use of a PDMP prior to prescribing opioids.

A Cross-sectional Examination of Vitamin D, Obesity, and Measures of Pain and Function in Middle-aged and Older Adults With Knee Osteoarthritis

OBJECTIVES

The prevalence of knee osteoarthritis (OA) is increasing with the aging population and is exacerbated by the growing numbers of obese older adults. Low levels of vitamin D, measured by serum 25-hydroxyvitamin D (25(OH)D), in older adults and obese individuals are correlated with several negative health conditions, including chronic pain. This cross-sectional study sought to examine the interactive influence of 25(OH)D levels and obesity on knee OA pain and functional performance measures.

METHODS

The sample consisted of 256 (63% female) racially diverse (55% black/African Americans) middle-aged and older adults (mean age 56.8 y). Blood was collected for analysis of 25(OH)D by high-performance liquid chromatography. Participants provided self-report regarding knee OA pain and underwent a lower extremity functional performance test.

RESULTS

Results demonstrated that obesity was associated with lower levels of 25(OH)D. Participants with adequate 25(OH)D levels reported significantly less knee OA pain compared with participants with deficient or insufficient levels, regardless of obesity status. Furthermore, there was a significant interaction between obesity and 25(OH)D levels for lower extremity functional performance, such that obese individuals with adequate 25(OH)D levels demonstrated better performance than those obese participants with deficient or insufficient 25(OH)D levels.

DISCUSSION

The mechanisms by which adequate 25(OH)D levels are associated with pain severity and improved function have not been completely elucidated. It may be that the pleiotropic role of biologically active 25(OH)D influences pain and pain processing through peripheral and central mechanisms. Alternatively, higher levels of pain may lead to reduced outdoor activity, which may contribute to both obesity and decreased vitamin D. Thus, investigating vitamin D status in obese and nonobese individuals with knee OA warrants further study.

Age Group Comparisons of TENS Response Among Individuals With Chronic Axial Low Back Pain

Chronic low back pain (CLBP) is a highly prevalent and disabling musculoskeletal pain condition among older adults. Transcutaneous electrical nerve stimulation (TENS) is commonly used to treat CLBP, however response to TENS in older adults compared with younger adults is untested. In a dose-response study stratified by age, 60 participants with axial CLBP (20 young, 20 middle-aged, 20 older) received four 20-minute sessions of high-frequency high-intensity TENS over a 2- to 3-week period in a laboratory-controlled setting. Experimental measures of pain sensitivity (mechanical pressure pain detection threshold) and central pain excitability (phasic heat temporal summation and heat aftersensations) were assessed before and after TENS. Episodic or immediate axial CLBP relief was assessed after TENS via measures of resting pain, movement-evoked-pain, and self-reported disability. Cumulative or prolonged axial CLBP relief was assessed by comparing daily pain reports across sessions. Independent of age, individuals experienced episodic increase in the pressure pain detection threshold and reduction in aftersensation after TENS application. Similarly, all groups, on average, experienced episodic axial CLBP relief via improved resting pain, movement-evoked pain, and disability report. Under this design, no cumulative effect was observed as daily pain did not improve for any age group across the 4 sessions. However, older adults received higher TENS amplitude across all sessions to achieve TENS responses similar to those in younger adults. These findings suggest that older adults experience similar episodic axial CLBP relief to that of younger individuals after high-frequency, high-intensity TENS when higher dose parameters are used.

PERSPECTIVE

This study examined age group differences in experimental and axial CLBP response to TENS, delivered under the current recommended parameters of strong, but tolerable amplitude. Older adults had comparable TENS response although at higher TENS amplitude than younger adults, which may have important mechanistic and clinical implications.

Successful aging: Advancing the science of physical independence in older adults

The concept of 'successful aging' has long intrigued the scientific community. Despite this long-standing interest, a consensus definition has proven to be a difficult task, due to the inherent challenge involved in defining such a complex, multi-dimensional phenomenon. The lack of a clear set of defining characteristics for the construct of successful aging has made comparison of findings across studies difficult and has limited advances in aging research. A consensus on markers of successful aging is furthest developed is the domain of physical functioning. For example, walking speed appears to be an excellent surrogate marker of overall health and predicts the maintenance of physical independence, a cornerstone of successful aging. The purpose of the present article is to provide an overview and discussion of specific health conditions, behavioral factors, and biological mechanisms that mark declining mobility and physical function and promising interventions to counter these effects. With life expectancy continuing to increase in the United States and developed countries throughout the world, there is an increasing public health focus on the maintenance of physical independence among all older adults.

Vitamin D status and pain sensitization in knee osteoarthritis: a critical review of the literature

Diagnostic imaging of disease severity has been found thus far to be a relatively modest predictor of knee osteoarthritis (OA) pain and disability, suggesting that other factors likely contribute to clinical symptoms in this condition. Recent evidence suggests that sensitization of the peripheral and central pathways that process nociceptive information (i.e., pain sensitization) is an important contributor to knee OA clinical symptoms. Furthermore, low levels of vitamin D have been found to be associated with the presence of pain sensitization, as well as the overall experience of clinical pain severity in knee OA. African-Americans with knee OA may be at increased risk for poor clinical outcomes given evidence of lower vitamin D levels as well as greater pain sensitization compared with non-Hispanic whites. Whether vitamin D supplementation is effective for alleviating knee OA clinical symptoms is an important topic to be addressed in future research with racially diverse samples that include sufficient numbers of African-Americans.

Inflammatory genes and psychological factors predict induced shoulder pain phenotype

PURPOSE

The pain experience has multiple influences, but little is known about how specific biological and psychological factors interact to influence pain responses. The current study investigated the combined influences of genetic (pro-inflammatory) and psychological factors on several preclinical shoulder pain phenotypes.

METHODS

An exercise-induced shoulder injury model was used, and a priori selected genetic (IL1B, TNF/LTA region, and IL6 single nucleotide polymorphisms (SNP)) and psychological (anxiety, depression symptoms, pain catastrophizing, fear of pain, and kinesiophobia) factors were included as the predictors of interest. The phenotypes were pain intensity (5-d average and peak reported on numerical rating scale), upper extremity disability (5-d average and peak reported on the Quick Disabilities of the Arm, Shoulder and Hand instrument), and duration of shoulder pain (d).

RESULTS

After controlling for age, sex, and race, the genetic and psychological predictors were entered separately as main effects and interaction terms in regression models for each pain phenotype. Results from the recruited cohort (n = 190) indicated strong statistical evidence for the interactions between 1) TNF/LTA SNP rs2229094 and depression symptoms for average pain intensity and duration and 2) IL1B two SNP diplotype and kinesiophobia for average shoulder pain intensity. Moderate statistical evidence for prediction of additional shoulder pain phenotypes included interactions of kinesiophobia, fear of pain, or depressive symptoms with TNF/LTA rs2229094 and IL1B.

CONCLUSIONS

These findings support the combined predictive ability of specific genetic and psychological factors for shoulder pain phenotypes by revealing novel combinations that may merit further investigation in clinical cohorts to determine their involvement in the transition from acute to chronic pain conditions.

Investigation of central pain processing in postoperative shoulder pain and disability

BACKGROUND

Measures of central pain processing like conditioned pain modulation and suprathreshold heat pain response (SHPR) have been described to assess different components of central pain modulatory mechanisms. Central pain processing potentially plays a role in the development of postsurgical pain, however, the role of conditioned pain modulation and SHPR in explaining postoperative clinical pain and disability is still unclear.

METHODS

Seventy-eight patients with clinical shoulder pain were included in this study. Patients were examined before shoulder surgery, at 3 months, and 6 months after surgery. The primary outcome measures were pain intensity and upper extremity disability.

RESULTS

Analyses revealed that the change score (baseline- 3 mo) of fifth pain rating of SHPR accounted for a significant amount of variance in 6-month postsurgical clinical pain intensity and disability after age, sex, preoperative pain intensity, and relevant psychological factors were considered.

CONCLUSIONS

The present study suggests that baseline measures of central pain processing were not predictive of 6-month postoperative pain outcome. Instead, the 3-month change in SHPR might be a relevant factor in the transition to an elevated 6-month postoperative pain and disability outcomes. In patients with shoulder pain, the 3-month change in a measure of central pain processing might be a relevant factor in the transition to elevated 6-month postoperative pain and disability scores.