Epidemiology of chronic pain, from the laboratory to the bus stop: time to add understanding of biological mechanisms to the study of risk factors in population-based research?

A cross-sectional study exploring relationships between triglyceride glucose index, atherogenic index of plasma, and chronic pain: NHANES 1999-2004

BACKGROUND

Triglyceride glucose (TyG) index and atherogenic index of plasma (AIP) are indicators of insulin resistance. However, inadequate evidence indicates that the TyG index, AIP, and chronic pain are linked.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) between 1999 and 2004 were used. Directed acyclic graphs were used to identify 11 potential confounders. The TyG index and AIP were treated as continuous variables in the multivariate logistic regression models to assess their association with chronic pain. Furthermore, the nonlinear relationships between these indices and outcomes were investigated using restricted cubic spline plots. Subsequently, subgroup analyses were conducted for the sensitive populations. Receiver operating characteristic curves were used to compare the relationships between indices and outcomes. Ultimately, two sensitivity analyses were performed.

RESULTS

This study identified nonlinear associations between the TyG index, AIP, and chronic pain in 16,996,513 Americans. The odds ratio and 95% confidence interval for the TyG index (per 1 standard deviation increase) was 1.17 (1.02, 1.33), and for AIP (per 1 standard deviation increase) was 1.19 (1.07, 1.34). According to the subgroup analyses, the relationships between exposure and outcome were more pronounced in the non-diabetic population. The TyG index and AIP performed similarly in assessing chronic pain in ROC curves. Additionally, the results of the two sensitivity analyses matched the conclusions of the main study.

CONCLUSIONS

Nonlinear correlations between the TyG index, AIP, and chronic pain were identified among adults in the United States. This demonstrated that the TyG index and AIP displayed similar effectiveness in predicting the risk of chronic pain.

Integrated Approach to Chronic Pain-The Role of Psychosocial Factors and Multidisciplinary Treatment: A Narrative Review

BACKGROUND

Chronic non-malignant pain represents a growing global public health priority. Chronic pain is multifactorial, with numerous biological, psychological, and social factors contributing to this pain syndrome. It affects not only the patients, impairing their quality of life, but also their family and social environment. Chronic pain is a diagnosis and requires effective and sustainable treatment strategies.

OBJECTIVE

Our aim was to critically review the available evidence on the importance of different approaches in treating patients with chronic non-malignant pain, emphasizing the effectiveness of integrating psychological and social factors within a multidisciplinary framework.

METHODS

This was a non-systematic narrative review of the basic and recent literature analyzing approaches to the treatment of chronic non-malignant pain. The inclusion criteria for the papers were chronic non-malignant pain, treatment approach, review, and original research papers published in English in the last five years (PubMed search), and the basic literature was selected from the references of new papers according to the knowledge and experience of the authors.

RESULTS

This literature review included 120 papers, of which 83 were basic, and 37 were new, published in the last 5 years (2018-2023). The results show that both the basic and newly published literature advocate for a biopsychosocial approach to treating chronic pain.

CONCLUSIONS

New findings, compared to the earlier literature, indicate a new classification of chronic pain into primary and secondary. Chronic pain should be approached with a biopsychosocial model within a multidisciplinary treatment framework. This model addresses the complex interplay of biological, psychological, and social factors, offering a holistic strategy for effective pain management.

Genetic Variants Influence the Development of Diabetic Neuropathy

The exact mechanism by which diabetic neuropathy develops is still not fully known, despite our advances in medical knowledge. Progressing neuropathy may occur with a persistently favorable metabolic status in some patients with diabetes mellitus, while, in others, though seldom, a persistently unfavorable metabolic status is not associated with significant neuropathy. This might be significantly due to genetic differences. While recent years have brought compelling progress in the understanding of the pathogenetic background-in particular, accelerated progress is being made in understanding molecular biological mechanisms-some aspects are still not fully understood. A comparatively small amount of information is accessible on this matter; therefore, by summarizing the available data, in this review, we aim to provide a clearer picture of the current state of knowledge, identify gaps in the previous studies, and possibly suggest directions for future studies. This could help in developing more personalized approaches to the prevention and treatment of diabetic neuropathy, while also taking into account individual genetic profiles.

Drug Safety and Suicidality Risk of Chronic Pain Medications

Chronic pain is one of the main leading causes of disability in the world at present. A variety in the symptomatology, intensity and duration of this phenomenon has led to an ever-increasing demand of pharmacological treatment and relief. This demand for medication, ranging from well-known groups, such as antidepressants and benzodiazepines, to more novel drugs, was followed by a rise in safety concerns of such treatment options. The validity, frequency, and diversity of such concerns are discussed in this paper, as well as their possible effect on future prescription practices. A specific caution is provided towards the psychological safety and toll of these medications, regarding suicidality and suicidal ideation. Most significantly, this paper highlights the importance of pharmacovigilance and underscores the necessity of surveillance programs when considering chronic pain medication.

The Relationship between Blood Lead Level and Chronic Pain in US Adults: A Nationwide Cross-Sectional Study

INTRODUCTION

Lead toxicity has been a major public health problem worldwide, yet no study has investigated the association between lead exposure and chronic pain.

METHODS

We used data from three cycles of National Health and Nutrition Examination Survey (NHANES) with chronic pain status. We conducted univariate and multivariate logistic regression analyses to investigate the association between chronic pain and blood lead level (BLL). Subgroup analyses were performed to explore which confounding factor modified the association between chronic pain and BLL.

RESULTS

A total of 13,485 participants were included in our final analysis, out of which 1950 (14.46%) had chronic pain. In the fully adjusted model, a 1 μg/dL increase of BLL was associated with 3% higher risk of chronic pain. The highest BLL quartile (BLL > 2.40 μg/dL) was associated with a 32% increase in the risk of chronic pain compared with the lowest BLL quartile (BLL < 0.90 μg/dL). In the subgroup analyses, hypertension (P for interaction = 0.018) and arthritis (P for interaction = 0.004) status modified the association between BLL and chronic pain. Higher quartiles of BLL were associated with a higher risk of chronic pain only in individuals with hypertension or arthritis but not those without these conditions.

CONCLUSION

A higher BLL was associated with a higher risk of chronic pain. Further research is warranted to investigate whether a causal relationship exists between the two, as well as potential underlying mechanisms.

Association between urinary phthalate levels and chronic pain in US adults, 1999-2004: A nationally representative survey

Introduction

Chronic pain is a public health concern throughout the world. Ascertaining and managing its risk factors helps develop well-directed treatment plans and prevention strategies. Phthalates (PAEs) exposure leads to various health problems. The present study aims to explore the potential correlation between urinary PAEs metabolites and chronic pain in adults.

Methods

The study population data were extracted from the National Health and Nutrition Examination Survey (NHANES) conducted from 1999 to 2004 in the United States. Seven urinary PAEs metabolites were used to assess long-term PAEs exposure. The assessment of chronic pain was determined by a self-report questionnaire. Weighted analyses were conducted to consider the complex sampling design. Models were adjusted by demographic data and lifestyle factors. Urinary PAEs metabolites were assessed as both continuous and categorical variables. Tertile 1 was considered as the reference. Stratified analyses were performed by gender and pain site. All data analyses were conducted with STATA, version 15.1. P < 0.05 was considered with statistical significance.

Results

A total of 4,196 participants were considered in our final analysis. Chronic pain prevalence reached 52.19% (n = 2,138) among the participants, with women accounting for a large proportion (57.75% vs. 42.25%). After multivariable logistic regression analysis, a higher prevalence of chronic pain was observed among participants in the third tertile of mono-(2-ethyl)-hexyl phthalate (MEHP) (OR = 1.23, 95% CI = 1.02-1.48, P = 0.034) and mono-benzyl phthalate (MBzP) (OR = 1.28, 95% CI = 1.04-1.58, P = 0.022) in our adjusted model. The logtransformed concentration of MBzP also showed a significant association with chronic pain prevalence (OR = 1.09, 95% CI = 1.01-1.18, P = 0.036) in the adjusted model. In further analysis, the positive correlations of urinary phthalate metabolites with chronic pain remained robust when stratified by gender and chronic pain site.

Conclusions

Our findings presented a positive correlation between urinary PAEs metabolites and chronic pain among adult participants, and more causal research should be conducted to ascertain the interactions between the two and to expound their underlying mechanisms.

The association of chronic pain and opioid withdrawal in men and women with opioid use disorder

BACKGROUND

Approximately 2.7 million individuals in the United States had an opioid use disorder (OUD) in 2020. Chronic pain may exacerbate opioid withdrawal severity, yet most research on opioid withdrawal has not collected data on chronic pain status. Moreover, there is limited evidence that women tend to experience greater opioid withdrawal severity than men, but large, confirmatory studies on this topic have not been published. The goal of this study was to examine the roles of chronic pain and gender on opioid withdrawal severity using a large, multi-site database.

METHODS

Data were collected from N = 1252 individuals with OUD entering eight residential addiction treatment facilities. Demographic, drug use behaviors, and chronic pain status were collected at treatment intake, and self-reported opioid withdrawal and craving were measured at intake and 1-3 days, 4-6 days, and 7-9 days after intake. Regression analyses were used to predict withdrawal and craving severity at intake and across the four timepoints.

RESULTS

At intake, withdrawal was higher in persons who were older, had greater SUD severity, women, had chronic pain, and used > 1 substance (p-values ≤.007) and craving was higher in persons with greater SUD severity (p < .001) and women (p = .033). Withdrawal remained higher in women and persons with chronic pain across timepoints but decreased at a similar rate relative to comparators.

CONCLUSIONS

Women and persons with chronic pain would benefit from earlier engagement in treatment and may require a more intensive strategy to mitigate opioid withdrawal in early treatment.

Relationships between Physical Activity Level and Pain in the Spanish Population: A Cross-Sectional Study

Introduction. One third of the world’s population suffers from some form of pain. Physical inactivity is one of the causes that reduces physical fitness and may lead to an increase in the prevalence of pain in the population. Aims. To analyse the relationships between the level of physical activity (PAL) and the prevalence and degree of pain, the limitations and impact of pain on daily activities and the use of pain medication in the Spanish population. Hypothesis. PAL is related to pain among Spaniards. Methodology. A cross-sectional study design was used, based on data obtained from the Spanish National Health Survey 2017 with 17,777 participants. A descriptive analysis was performed. Nonparametric statistical tests were used: chi-square statistic to analyse intergroup differences in ordinal variables; Mann−Whitney U test to analyse intergroup differences in continuous variables. A correlation study was also performed between the variables of interest, using Spearman’s rho. Results. Relationships were found between PAL and: prevalence of pain, degree of pain, limitations due to pain in usual activities, level of impact in daily activities and use of pain medication in the Spanish population (p < 0.001). Performing moderate and intense PA was related to lower prevalence and degree of pain in the population that performed it, compared to those who only walked or were inactive. Weak correlations were found between the level of PA and the study variables (p < 0.001). Conclusions. High PALs in the population are related to better indicators of pain among Spaniards, appearing to reduce the prevalence and degree of pain, as well as the limitations and impact caused by pain in the daily activities of citizens, and could reduce the use of pain medication in the adult Spanish population.

Individuals' beliefs about the biopsychosocial factors that contribute to their chronic musculoskeletal pain: protocol for a qualitative study in the UK

INTRODUCTION

Chronic musculoskeletal pain (CMP) is described as pain that persists for longer than 3 months. At present, no research is available that understands why CMP develops and continues from the perspective of the individual. Research is needed to establish if there are any consistent biopsychosocial factors perceived as contributing to CMP and what informs such beliefs. Understanding individual beliefs will inform more effective communication between clinicians and patients about their CMP, as well as informing future research into the epidemiology of CMP. Interpretative phenomenological analysis will be used as a methodological framework as it explores how individuals make sense of their world through personal experiences and perceptions while preserving individual nuance. The aim of this study is to understand individuals' beliefs and perceptions about the biological, psychological and social factors, which contribute to the development and maintenance of their CMP.

METHODS AND ANALYSIS

A qualitative study informed by the Consolidated Criteria for Reporting Qualitative Research using interpretative phenomenological analysis and semistructured interviews. A maximum variation purposive sample of 6-12 adults with CMP will be recruited from the general public in the UK. One semistructured interview will be conducted with each participant via an online video platform with interviews transcribed verbatim. The interview schedule (codesigned with expert patients and informed by existing evidence) identifies three domains of important questions; (1) patient beliefs on why they developed and continue to experience CMP; (2) the relationship between their biopsychosocial experiences and CMP; and (3) the origin of their beliefs. Strategies such as 'member checking' will be employed to ensure trustworthiness.

ETHICS AND DISSEMINATION

Ethical approval was granted by the Research Ethics Office at the University of Birmingham (reference ERN_21-0813). Informed consent will be obtained from all participants. The study findings will be submitted for publication in a peer-reviewed journal and for presentation at conferences.

Exercise Improves the Impact of Chronic Pain in Older Adults: Results of an RCT

Background:

Chronic Pain (CP) is a crucial determinant for disability in older adults. CP amplifies the impact of other common age-related diseases and increases cardiovascular risk. Physical exercise can improve CP. Randomized Controlled Trials (RCTs) with high-intensity exercise in older adults excluded people with Moderate Chronic Illness (MCI) and CP.

Objective:

This study aimed at evaluating in an RCT whether moderate exercise training can improve chronic pain in a sample of older adults, including people with MCI, and if any modification persists over time.

Methods:

A sample of 120 older adults was randomly selected for a moderate-intensity exercise program or cultural activities (control group). Chronic pain was assessed at t0, at t12 (end of the trial), and t48 weeks, by means of the Italian version of the SIP-Roland Scale.

Results:

Seventy-nine participants completed the follow-up (age 72.3±4.7, women 55.3%). At the end of RCT, an improvement in the SIP scale score was found in the exercise group (p=0.035), showing a lower score than the control group; this difference was not maintained at 48 weeks (p=0.235).

Conclusion:

Our study highlighted that a moderate-intensity exercise intervention reduced chronic pain in older adults, but this effect disappeared at follow-up after 36 weeks from the end of the training program. These findings suggested that such kinds of programs, easily accessible to old people even with MCI, should be implemented and supported over time, thus promoting active aging and preventing CP of age-related diseases.

Clinical Trial Registration: Clinical.Trials.gov.NCT03858114

Non-Medical Factors Associated with the Outcome of Treatment of Chronic Non-Malignant Pain: A Cross-Sectional Study

BACKGROUND

Chronic pain is a global public health issue with increasing prevalence. Chronic pain causes sleep disorder, reactive anxiety, and depression, impairs the quality of life; it burdens the individual and society as a whole. The aim of this study was to examine non-medical factors related to the outcome of the treatment of chronic non-malignant pain.

METHODS

A cross-sectional study with two groups of patients was conducted using a questionnaire with biological, psychological, and social characteristics of patients. Since this study was cross-sectional, it was not possible to determine whether some factors were the cause or the consequence of unsuccessful treatment outcome, which is at the same time one of the disadvantages of cross-sectional studies.

RESULTS

The poor outcome of the treatment of chronic non-malignant pain in a multivariate binary logistic regression model was statistically significantly associated with the lower quality of life (OR = 0.95 (95% CI: 0.91-0.99; p = 0.009), and higher depression level OR = 1.08 (95% CI: 1.02-1.14; p = 0.009). The outcome of the treatment was not directly related to social support measured by the multivariate binary logistic regression model (OR = 1.04, 95% CI: 0.95-1.15, p = 0.395), but solitary life (without partner) was (OR = 2.16 (95% CI: 1.03-4.53; p = 0.043).

CONCLUSION

The typical patient with a poor pain management outcome is retired, presents depressive behavior; their pain disturbs general activity and sleeping. Moreover, they have a physically disturbed quality of life and require self-treatment due to the inaccessibility of doctors and therapies. The principle of treatment of patients with chronic, non-malignant pain should take into account a biopsychosocial approach with individually adjusted procedures.

Chronic widespread pain in children and adolescents presenting in primary care: prevalence and associated risk factors

ABSTRACT

A significant proportion of children/adolescents report chronic widespread pain (CWP), but little is known about clinically relevant CWP or what factors lead to onset in this population. Objectives were to report the primary care consultation prevalence of CWP and investigate risk factors associated with onset. A validated algorithm for identifying CWP status from primary care electronic healthcare records was applied to a child or adolescent population (aged 8-18 years). The algorithm records patients who have recurrent pain consultations (axial skeleton and upper or lower limbs) or those with a nonspecific generalised pain disorder (eg, fibromyalgia). Prevalence was described, and a nested case-control study was established to identify risk factors associated with CWP onset using logistic regression producing odds ratios (ORs) and 95% confidence intervals (95% CIs). Two hundred seventy-one children or adolescents were identified with CWP, resulting in a 5-year consultation prevalence of 3.19%. Risk factors significantly associated with CWP onset were as follows: mental health (eg, anxiety/neurosis consultations), neurological (eg, headaches), genitourinary (eg, cystitis), gastrointestinal (eg, abdominal pain), and throat problems (eg, sore throats). Children or adolescents with 1 or 2 risk factors (OR 2.15, 95% CI 1.6-2.9) or 3 or more risk factors (OR 9.17, 95% CI 5.9-14.3) were at significantly increased odds of CWP onset compared with those with none. Findings show a significant proportion of the child or adolescent primary care population has CWP. Most risk factors involved pain-related conditions, suggesting potential pathways of pain development. Further work is now needed to better understand the development of CWP in children and adolescents.

Protective role of natural killer cells in neuropathic pain conditions

ABSTRACT

During the past few years, the research of chronic neuropathic pain has focused on neuroinflammation within the central nervous system and its impact on pain chronicity. As part of the ERA-Net NEURON consortium, we aimed to identify immune cell patterns in the cerebrospinal fluid (CSF) of patients with herpes zoster neuralgia and patients with polyneuropathy (PNP), which may contribute to pain chronicity in these neuropathic pain conditions. Cerebrospinal fluid of 41 patients (10 herpes zoster and 31 PNP) was analyzed by flow cytometry identifying lymphocyte subsets: CD4+ (T-helper cells), CD8+ (cytotoxic T cells), CD19+ (B cells), and CD56+ (natural killer [NK]) cells. At baseline and at follow-up, the somatosensory phenotype was assessed with quantitative sensory testing. In addition, the patients answered epidemiological questionnaires and the PainDETECT questionnaire. Immune cell profiles and somatosensory profiles, as well as painDETECT questionnaire scores, were analyzed and correlated to determine specific immune cell patterns, which contribute to chronic pain. We found a negative correlation (P = 0.004, r = -0.596) between the frequency of NK cells and mechanical pain sensitivity (MPS), one of the most relevant quantitative sensory testing markers for central sensitization; a high frequency of NK cells correlated with low MPS. The analysis of the individual follow-up showed a worsening of the pain condition if NK-cell frequency was low. Low NK-cell frequency is associated with signs of central sensitization (MPS), whereas high NK-cell frequency might prevent central sensitization. Therefore, NK cells seem to play a protective role within the neuroinflammatory cascade and may be used as a marker for pain chronicity.

Long-term trajectories of chronic musculoskeletal pain: a 21-year prospective cohort latent class analysis

ABSTRACT

Our knowledge of the prevalence, impact, and outcomes of chronic pain in the general population is predominantly based on studies over relatively short periods of time. The aim of this study was to identify and describe trajectories of the chronic pain status over a period of 21 years. Self-reported population data (n = 1858) from 5 timepoints were analyzed. Pain was categorized by: no chronic pain (NCP), chronic regional pain (CRP), and chronic widespread pain (CWP). Latent class growth analysis was performed for identification of trajectories and logistic regression analysis for identification of predictors for pain prognosis. Five trajectories were identified: (1) persistent NCP (57%), (2) migrating from NCP to CRP or CWP (5%), (3) persistent CRP or migration between CRP and NCP (22%), (4) migration from CRP to CWP (10%), and (5) persistent CWP (6%). Age, sleeping problems, poor vitality, and physical function at baseline were associated with pain progression from NCP. Female gender, seeking care for pain, lack of social support, poor physical function, vitality, and mental health predicted poor pain prognosis among those with CRP. In conclusion, chronic pain was common in the population including 6% reporting persistent CWP, although the majority persistently reported NCP. Most people had stable pain status, but some had ongoing change in pain status over time including people who improved from chronic pain. It was possible to identify clinically relevant factors, characterizing trajectories of chronic pain development, that can be useful for identifying individuals at risk and potential targets for intervention.

Chronic Pain and Friendship among Middle-Aged and Older U.S. Adults

OBJECTIVES

This study examines how chronic pain affects friendship in later life. We test whether onset of pain leads to social network activation, as suggested by research on other health conditions (Latham- Mintus, Forth.), or whether pain-an unverifiable and often stigmatizing condition-functions as a "threat to the social self" (Karos et al., 2018).

METHODS

Using longitudinal data from the Health and Retirement Study (HRS; N=4,598; 2006/2008 as Time 1 and 2010/2012 as Time 2), we conducted OLS regressions with the lagged dependent variable approach to assess how new-onset chronic pain predicted (a) respondents' number of close friends and (b) their frequency of in-person meetings with friends, controlling for sociodemographic variables and health conditions.

RESULTS

New-onset severe pain predicted a decrease in number of friends. New-onset moderate pain, in contrast, predicted more friends and more frequent in-person meetings. (Findings were significant or marginally significant depending on model specifications.) Mild pain showed no significant association with either outcome. Pain had a greater effect on men's friendship outcomes than women's.

DISCUSSION

The effects of chronic pain on later-life friendships appear to depend on pain severity, and to differ between men and women. Onset of severe pain serves as a "threat to the social self," while onset of moderate pain contributes to social network activation; both associations are significantly more pronounced among men. These findings highlight the complex associations between health and social outcomes.

Hip Disability and Osteoarthritis Outcome Score (HOOS): A Cross-Cultural Validation of the Brazilian Portuguese Version Study

Objective  Translated and validated outcome instruments are of great importance, since they can be used for researchers studying different populations with the same problem. The objective of the present study was to translate, culturally adapt and validate the Hip Disability and Osteoarthritis Outcome Score (HOOS) into Brazilian Portuguese.

Methods  The HOOS was translated from English into Brazilian Portuguese, translated back into English, and submitted to an experts committee. It was administered to 100 patients with hip osteoarthritis. The psychometric evaluation included factor analysis; internal reliability measures, test-retest reliability at 7 days, and construct validity comparison with the Brazilian version of the Graded Chronic Pain Scale (GCPS).

Results  Factor analyses demonstrated a five-factor solution. The test-retest reliability showed a high degree of internal consistency for the five subscales ( pain and physical difficulties , 0.97 at baseline and 0.93 at 7 days; pain and difficulty sitting, lying down and getting up , 0.93 at baseline and 0.89 at 7 days; difficulty flexing the knee , 0.92 at baseline and 0.83 at 7 days; difficulty walking , 0.88 at baseline and 0.87 at 7 days; quality of life , 0.80 at baseline and 0.35 at 7 days). The construct validity was established during the comparison of the Brazilian version of the GCPS.

Conclusions  A Brazilian version of the HOOS was developed with adequate reliability and validity. It will facilitate evaluation of the hip within a large patient population and across cultures.

The prevalence of chronic pain and its associated factors among Saudi Al-Kharj population; a cross sectional study

BACKGROUND

Chronic pain (CP) can be a symptom of many underlying health issues. The consequences of CP may vary from slight discomfort to disruption of quality of life and normal functioning. In this study, we aim to investigate the prevalence of CP and its associated factors in Al Kharj, Saudi Arabia.

METHODS

This was a cross-sectional study conducted in Al Kharj, Saudi Arabia. We recruited 1031 participants for our study. Data was collected on socio-demographic, health predictors and anthropometric measurements (such as weight, height and waist circumference). The data analysis was performed on JMP®, Version 12. SAS Institute Inc., Cary, NC, 1989-2007.

RESULTS

The prevalence of self-reported chronic pain in Al Kharj population was 19% with a mean age of 26.4 (SD = 8.6) years. The most common locations of pain included; back pain (30%), abdominal pain (26%), headache (13%), and any musculoskeletal pain (56%). Multiple logistic regression revealed that presence of a chronic disease (OR = 3.8; 95% CI = 2.3-6.2), psychological disease (OR = 2.3; 95% CI = 1.2-4.3), high General Health Questionnaire (GHQ)-12 score (OR = 1.06; 95% CI = 1.03-1.1), and pack-years of smoking (OR = 1.05; 95% CI = 1.01-1.08) were significantly related to chronic pain in Al Kharj population.

CONCLUSIONS

Our study results found a high burden of chronic pain in this selected Saudi population. The most prevalent pain was low back pain. The presence of chronic and psychological diseases were strongly related to chronic pain. Future prospective studies are needed to establish the temporal relationship of chronic pain with these factors.

Pain management in patients with vascular disease

Vascular disease covers a wide range of conditions, including arterial, venous, and lymphatic disorders, with many of these being more common in the elderly. As the population ages, the incidence of vascular disease will increase, with a consequent increase in the requirement to manage both acute and chronic pain in this patient population. Pain management can be complex, as there are often multiple co-morbidities to be considered. An understanding of the underlying pain mechanisms is helpful in the logical direction of treatment, particularly in chronic pain states, such as phantom limb pain or complex regional pain syndrome. Acute pain management for vascular surgery presents a number of challenges, including coexisting anticoagulant medication, that may preclude the use of regional techniques. Within the limited evidence base, there is a suggestion that epidural analgesia provides better pain relief and reduced respiratory complications after major vascular surgery. For carotid endarterectomy, there is again some evidence supporting the use of local anaesthetic analgesia, either by infiltration or by superficial cervical plexus block. Chronic pain in vascular disease includes post-amputation pain, for which well-known risk factors include high pain levels before amputation and in the immediate postoperative period, emphasizing the importance of good pain control in the perioperative period. Complex regional pain syndrome is another challenging chronic pain syndrome with a wide variety of treatment options available, with the strongest evidence being for physical therapies. Further research is required to gain a better understanding of the underlying pathophysiological mechanisms in pain associated with vascular disease and the best analgesic approaches to manage it.

Serum vitamin C and spinal pain: a nationwide study

Back pain brings about one of the heaviest burden of disease. Despite much research, this condition remains poorly understood, and effective treatments are frustratingly elusive. Thus, researchers in the field need to consider new hypotheses. Vitamin C (ascorbic acid) is an essential cofactor for collagen crosslinks, a key determinant of ligament, tendon, and bone quality. Recent studies have reported high frequency of hypovitaminosis C in the general population. We hypothesized that lack of vitamin C contributes to poor collagen properties and back pain. We conducted this study to examine the associations between serum concentration of vitamin C and the prevalence of spinal pain and related functional limitations in the adult general population. This study used nationwide cross-sectional data from the U.S. National Health and Nutrition Examination Survey (NHANES) 2003-2004. Data were available for 4742 individuals aged ≥20 years. Suboptimal serum vitamin C concentrations were associated with the prevalence of neck pain (adjusted odds ratio [aOR]: 1.5; 95% confidence interval [CI]: 1.2-2.0), low back pain (aOR: 1.3; 95% CI: 1.0-1.6), and low back pain with pain below knee (aOR: 1.3; 95% CI: 1.0-1.9) in the past 3 months, self-reported diagnosis of arthritis/rheumatism (aOR: 1.4; 95% CI: 1.2-1.7), and related functional limitations' score (adjusted difference of means [aB]: 0.03; 95% CI: 0.00-0.05). The prevalence of hypovitaminosis C in the general population is high. Our study shows associations between vitamin C and spinal pain that warrant further investigation to determine the possible importance of vitamin C in the treatment of back pain patients.

Physical activity and exercise for chronic pain in adults: an overview of Cochrane Reviews

BACKGROUND

Chronic pain is defined as pain lasting beyond normal tissue healing time, generally taken to be 12 weeks. It contributes to disability, anxiety, depression, sleep disturbances, poor quality of life, and healthcare costs. Chronic pain has a weighted mean prevalence in adults of 20%.For many years, the treatment choice for chronic pain included recommendations for rest and inactivity. However, exercise may have specific benefits in reducing the severity of chronic pain, as well as more general benefits associated with improved overall physical and mental health, and physical functioning.Physical activity and exercise programmes are increasingly being promoted and offered in various healthcare systems, and for a variety of chronic pain conditions. It is therefore important at this stage to establish the efficacy and safety of these programmes, and furthermore to address the critical factors that determine their success or failure.

OBJECTIVES

To provide an overview of Cochrane Reviews of adults with chronic pain to determine (1) the effectiveness of different physical activity and exercise interventions in reducing pain severity and its impact on function, quality of life, and healthcare use; and (2) the evidence for any adverse effects or harm associated with physical activity and exercise interventions.

METHODS

We searched theCochrane Database of Systematic Reviews (CDSR) on the Cochrane Library (CDSR 2016, Issue 1) for systematic reviews of randomised controlled trials (RCTs), after which we tracked any included reviews for updates, and tracked protocols in case of full review publication until an arbitrary cut-off date of 21 March 2016 (CDSR 2016, Issue 3). We assessed the methodological quality of the reviews using the AMSTAR tool, and also planned to analyse data for each painful condition based on quality of the evidence.We extracted data for (1) self-reported pain severity, (2) physical function (objectively or subjectively measured), (3) psychological function, (4) quality of life, (5) adherence to the prescribed intervention, (6) healthcare use/attendance, (7) adverse events, and (8) death.Due to the limited data available, we were unable to directly compare and analyse interventions, and have instead reported the evidence qualitatively.

MAIN RESULTS

We included 21 reviews with 381 included studies and 37,143 participants. Of these, 264 studies (19,642 participants) examined exercise versus no exercise/minimal intervention in adults with chronic pain and were used in the qualitative analysis.Pain conditions included rheumatoid arthritis, osteoarthritis, fibromyalgia, low back pain, intermittent claudication, dysmenorrhoea, mechanical neck disorder, spinal cord injury, postpolio syndrome, and patellofemoral pain. None of the reviews assessed 'chronic pain' or 'chronic widespread pain' as a general term or specific condition. Interventions included aerobic, strength, flexibility, range of motion, and core or balance training programmes, as well as yoga, Pilates, and tai chi.Reviews were well performed and reported (based on AMSTAR), and included studies had acceptable risk of bias (with inadequate reporting of attrition and reporting biases). However the quality of evidence was low due to participant numbers (most included studies had fewer than 50 participants in total), length of intervention and follow-up (rarely assessed beyond three to six months). We pooled the results from relevant reviews where appropriate, though results should be interpreted with caution due to the low quality evidence. Pain severity: several reviews noted favourable results from exercise: only three reviews that reported pain severity found no statistically significant changes in usual or mean pain from any intervention. However, results were inconsistent across interventions and follow-up, as exercise did not consistently bring about a change (positive or negative) in self-reported pain scores at any single point. Physical function: was the most commonly reported outcome measure. Physical function was significantly improved as a result of the intervention in 14 reviews, though even these statistically significant results had only small-to-moderate effect sizes (only one review reported large effect sizes). Psychological function and quality of life: had variable results: results were either favourable to exercise (generally small and moderate effect size, with two reviews reporting significant, large effect sizes for quality of life), or showed no difference between groups. There were no negative effects. Adherence to the prescribed intervention: could not be assessed in any review. However, risk of withdrawal/dropout was slightly higher in the exercising group (82.8/1000 participants versus 81/1000 participants), though the group difference was non-significant. Healthcare use/attendance: was not reported in any review. Adverse events, potential harm, and death: only 25% of included studies (across 18 reviews) actively reported adverse events. Based on the available evidence, most adverse events were increased soreness or muscle pain, which reportedly subsided after a few weeks of the intervention. Only one review reported death separately to other adverse events: the intervention was protective against death (based on the available evidence), though did not reach statistical significance.

AUTHORS' CONCLUSIONS

The quality of the evidence examining physical activity and exercise for chronic pain is low. This is largely due to small sample sizes and potentially underpowered studies. A number of studies had adequately long interventions, but planned follow-up was limited to less than one year in all but six reviews.There were some favourable effects in reduction in pain severity and improved physical function, though these were mostly of small-to-moderate effect, and were not consistent across the reviews. There were variable effects for psychological function and quality of life.The available evidence suggests physical activity and exercise is an intervention with few adverse events that may improve pain severity and physical function, and consequent quality of life. However, further research is required and should focus on increasing participant numbers, including participants with a broader spectrum of pain severity, and lengthening both the intervention itself, and the follow-up period.

Use of analgesics in young adults as a predictor of health care utilization and pain prevalence: Israel defense forces experience

Pain evaluation in large community studies is difficult. Analgesics can be a useful tool in estimating pain-related conditions in which analgesic use is highly regulated. In this study, we evaluated analgesics consumption patterns of regular Israel Defense Force soldiers. We have performed a historical cohort study of 665,137 young adults during active duty in 2002 to 2012. Analgesics were prescribed to 518,242 (78%) soldiers, mostly for musculoskeletal pain (69.3%), abdominal pain (12.7%), and headache (12.1%). Acute (1-14 days), subacute (15-90), and chronic (>90 days) analgesic use episodes were experienced by 396,987 (59.7%), 74,591 (11.2%), and 46,664 (7%) of the population. In a multivariate model, predictors for chronic analgesics use were as follows: low intelligence, service in a combat supporting unit, previous pain diagnosis, male sex, Israeli nativity, low socioeconomic status, and high body mass index. Low intelligence had the highest odds ratio for chronic analgesic consumption (2.1) compared with other predictors. Chronic analgesic use was associated with a significant increase in health care utilization cost per year (911$ per soldier vs 199$ for nonusers), increased sick leave days per year (7.09 vs 0.67 for nonusers), and higher dropout rate from combat units (25% vs 9.2% for nonusers). Chronic use of analgesics is common among young adults, and it is an important predictor for unsuccessful military service and high health care utilization costs. Further studies in other setups are indicated.

Physical activity and exercise for chronic pain in adults: an overview of Cochrane Reviews

BACKGROUND

Chronic pain is defined as pain lasting beyond normal tissue healing time, generally taken to be 12 weeks. It contributes to disability, anxiety, depression, sleep disturbances, poor quality of life, and healthcare costs. Chronic pain has a weighted mean prevalence in adults of 20%.For many years, the treatment choice for chronic pain included recommendations for rest and inactivity. However, exercise may have specific benefits in reducing the severity of chronic pain, as well as more general benefits associated with improved overall physical and mental health, and physical functioning.Physical activity and exercise programmes are increasingly being promoted and offered in various healthcare systems, and for a variety of chronic pain conditions. It is therefore important at this stage to establish the efficacy and safety of these programmes, and furthermore to address the critical factors that determine their success or failure.

OBJECTIVES

To provide an overview of Cochrane Reviews of adults with chronic pain to determine (1) the effectiveness of different physical activity and exercise interventions in reducing pain severity and its impact on function, quality of life, and healthcare use; and (2) the evidence for any adverse effects or harm associated with physical activity and exercise interventions.

METHODS

We searched theCochrane Database of Systematic Reviews (CDSR) on the Cochrane Library (CDSR 2016, Issue 1) for systematic reviews of randomised controlled trials (RCTs), after which we tracked any included reviews for updates, and tracked protocols in case of full review publication until an arbitrary cut-off date of 21 March 2016 (CDSR 2016, Issue 3). We assessed the methodological quality of the reviews using the AMSTAR tool, and also planned to analyse data for each painful condition based on quality of the evidence.We extracted data for (1) self-reported pain severity, (2) physical function (objectively or subjectively measured), (3) psychological function, (4) quality of life, (5) adherence to the prescribed intervention, (6) healthcare use/attendance, (7) adverse events, and (8) death.Due to the limited data available, we were unable to directly compare and analyse interventions, and have instead reported the evidence qualitatively.

MAIN RESULTS

We included 21 reviews with 381 included studies and 37,143 participants. Of these, 264 studies (19,642 participants) examined exercise versus no exercise/minimal intervention in adults with chronic pain and were used in the qualitative analysis.Pain conditions included rheumatoid arthritis, osteoarthritis, fibromyalgia, low back pain, intermittent claudication, dysmenorrhoea, mechanical neck disorder, spinal cord injury, postpolio syndrome, and patellofemoral pain. None of the reviews assessed 'chronic pain' or 'chronic widespread pain' as a general term or specific condition. Interventions included aerobic, strength, flexibility, range of motion, and core or balance training programmes, as well as yoga, Pilates, and tai chi.Reviews were well performed and reported (based on AMSTAR), and included studies had acceptable risk of bias (with inadequate reporting of attrition and reporting biases). However the quality of evidence was low due to participant numbers (most included studies had fewer than 50 participants in total), length of intervention and follow-up (rarely assessed beyond three to six months). We pooled the results from relevant reviews where appropriate, though results should be interpreted with caution due to the low quality evidence. Pain severity: several reviews noted favourable results from exercise: only three reviews that reported pain severity found no statistically significant changes in usual or mean pain from any intervention. However, results were inconsistent across interventions and follow-up, as exercise did not consistently bring about a change (positive or negative) in self-reported pain scores at any single point. Physical function: was the most commonly reported outcome measure. Physical function was significantly improved as a result of the intervention in 14 reviews, though even these statistically significant results had only small-to-moderate effect sizes (only one review reported large effect sizes). Psychological function and quality of life: had variable results: results were either favourable to exercise (generally small and moderate effect size, with two reviews reporting significant, large effect sizes for quality of life), or showed no difference between groups. There were no negative effects. Adherence to the prescribed intervention: could not be assessed in any review. However, risk of withdrawal/dropout was slightly higher in the exercising group (82.8/1000 participants versus 81/1000 participants), though the group difference was non-significant. Healthcare use/attendance: was not reported in any review. Adverse events, potential harm, and death: only 25% of included studies (across 18 reviews) actively reported adverse events. Based on the available evidence, most adverse events were increased soreness or muscle pain, which reportedly subsided after a few weeks of the intervention. Only one review reported death separately to other adverse events: the intervention was protective against death (based on the available evidence), though did not reach statistical significance.

AUTHORS' CONCLUSIONS

The quality of the evidence examining physical activity and exercise for chronic pain is low. This is largely due to small sample sizes and potentially underpowered studies. A number of studies had adequately long interventions, but planned follow-up was limited to less than one year in all but six reviews.There were some favourable effects in reduction in pain severity and improved physical function, though these were mostly of small-to-moderate effect, and were not consistent across the reviews. There were variable effects for psychological function and quality of life.The available evidence suggests physical activity and exercise is an intervention with few adverse events that may improve pain severity and physical function, and consequent quality of life. However, further research is required and should focus on increasing participant numbers, including participants with a broader spectrum of pain severity, and lengthening both the intervention itself, and the follow-up period.

A genome-wide association study suggests an association of Chr8p21.3 (GFRA2) with diabetic neuropathic pain

Background

Neuropathic pain, caused by a lesion or a disease affecting the somatosensory system, is one of the most common complications in diabetic patients. The purpose of this study is to identify genetic factors contributing to this type of pain in a general diabetic population.

Method

We accessed the Genetics of Diabetes Audit and Research Tayside (GoDARTS) datasets that contain prescription information and monofilament test results for 9439 diabetic patients, among which 6927 diabetic individuals were genotyped by Affymetrix SNP6.0 or Illumina OmniExpress chips. Cases of neuropathic pain were defined as diabetic patients with a prescription history of at least one of five drugs specifically indicated for the treatment of neuropathic pain and in whom monofilament test result was positive for sensory neuropathy in at least one foot. Controls were individuals who did not have a record of receiving any opioid analgesics. Imputation of non‐genotyped SNPs was performed by IMPUTE2, with reference files from 1000 Genomes Phase I datasets.

Results

After data cleaning and relevant exclusions, imputed genotypes of 572 diabetic neuropathic pain cases and 2491 diabetic controls were used in the Fisher's exact test. We identified a cluster in the Chr8p21.3, next to GFRA2 with a lowest p‐value of 1.77 × 10⁻⁷ at rs17428041. The narrow‐sense heritability of this phenotype was 11.00%.

Conclusion

This genome‐wide association study on diabetic neuropathic pain suggests new evidence for the involvement of variants near GFRA2 with the disorder, which needs to be verified in an independent cohort and at the molecular level.

Neuropathic pain phenotyping by international consensus (NeuroPPIC) for genetic studies: a NeuPSIG systematic review, Delphi survey, and expert panel recommendations

For genetic research to contribute more fully to furthering our knowledge of neuropathic pain, we require an agreed, valid, and feasible approach to phenotyping, to allow collaboration and replication in samples of sufficient size. Results from genetic studies on neuropathic pain have been inconsistent and have met with replication difficulties, in part because of differences in phenotypes used for case ascertainment. Because there is no consensus on the nature of these phenotypes, nor on the methods of collecting them, this study aimed to provide guidelines on collecting and reporting phenotypes in cases and controls for genetic studies. Consensus was achieved through a staged approach: (1) systematic literature review to identify all neuropathic pain phenotypes used in previous genetic studies; (2) Delphi survey to identify the most useful neuropathic pain phenotypes and their validity and feasibility; and (3) meeting of experts to reach consensus on the optimal phenotype(s) to be collected from patients with neuropathic pain for genetic studies. A basic "entry level" set of phenotypes was identified for any genetic study of neuropathic pain. This set identifies cases of "possible" neuropathic pain, and controls, and includes: (1) a validated symptom-based questionnaire to determine whether any pain is likely to be neuropathic; (2) body chart or checklist to identify whether the area of pain distribution is neuroanatomically logical; and (3) details of pain history (intensity, duration, any formal diagnosis). This NeuroPPIC "entry level" set of phenotypes can be expanded by more extensive and specific measures, as determined by scientific requirements and resource availability.

A Genome-wide Association Study Provides Evidence of Sex-specific Involvement of Chr1p35.1 (ZSCAN20-TLR12P) and Chr8p23.1 (HMGB1P46) With Diabetic Neuropathic Pain

Neuropathic pain is defined as pain arising as a direct consequence of a lesion or a disease affecting the somatosensory system and it affects around 1 in 4 diabetic patients in the UK. The purpose of this genome-wide association study (GWAS) was to identify genetic contributors to this disorder. Cases of neuropathic pain were defined as diabetic patients with a multiple prescription history of at least one of five drugs specifically indicated for the treatment of neuropathic pain. Controls were diabetic individuals who were not prescribed any of these drugs, nor amitriptyline, carbamazepine, or nortriptyline. Overall, 961 diabetic neuropathic pain cases and 3260 diabetic controls in the Genetics of Diabetes Audit and Research Tayside (GoDARTS) cohort were identified. We found a cluster in the Chr1p35.1 (ZSCAN20-TLR12P) with a lowest P value of 2.74 × 10(- 7) at rs71647933 in females and a cluster in the Chr8p23.1, next to HMGB1P46 with a lowest P value of 8.02 × 10(- 7) at rs6986153 in males. Sex-specific narrow sense heritability was higher in males (30.0%) than in females (14.7%). This GWAS on diabetic neuropathic pain provides evidence for the sex-specific involvement of Chr1p35.1 (ZSCAN20-TLR12P) and Chr8p23.1 (HMGB1P46) with the disorder, indicating the need for further research.

Attrition with spinal cord stimulation

The aim of this prospective study was to investigate whether spinal cord stimulation (SCS) significantly reduces pain intensity for up to 18-month follow-up in patients with chronic neuropathic pain. Forty-eight patients were recruited. Patients rated their pain using a Visual analog scale (VAS) and pain-related disability using the Oswestry Disability Index (ODI) at baseline (1 week prior to SCS surgery) and at 6-, 12-, and 18-month follow-up. Pain intensity significantly decreased from baseline to all 3 time points [F (3,135) = 16.264, p < 0.001]. The greatest difference in the reduction of pain intensity was observed between baseline (M = 7.20, SD = 1.34) and 6-month follow-up (M = 4.60, SD = 2.20), [t(47) = 6.741, p < 0.001]. However, when looking at differences between the 6-month follow-up and subsequent assessments, statistically significant increases in pain intensity from the 6-month to the 12-month follow-up [t(47) = -2.788, p = 0.008], and from the 6-month to the 18-month follow-up [t(47) = -3.339, p = 0.002] could be observed. Statistically significant changes were also observed for clinical changes in pain scores [F (2,94) = 4.972, p = 0.009. There was a significant decrease in the percentage of clinical change obtained from the 6-month (M = 33.19, SD = 35.63) to the 12-month follow-up (M = 23.76, SD = 33.62), [t(47) = 2.347, p = 0.025], and from the 6-month to the 18-month follow-up (M = 18.34, SD = 33.51), [t(47) = 3.072, p = 0.004]. A number of patients also reported higher levels of pain intensity at the 12-and 18-month follow-up than at baseline. Pain-related disability scores significantly decreased from baseline (M = 55.04, SD = 16.43) to the 6-month follow up (M = 46.98, SD = 19.05), [t(47) = 3.464, p = 0.001] and from baseline to the 12-month follow up (M = 48.49, SD = 20.94), [t(47) = 2.918, p = 0.005], but not during the 18-month follow up (M = 51.75, SD = 20.92), [t(47) = 1.330, p = .190]. There was a significant increase in pain-related disability between the 6- and the 18-month follow up [t(47) = -2.188. p = 0.034]. These findings suggest that the beneficial effect of SCS on pain intensity may diminish over time, and that the 6-month follow-up scores may reflect a placebo effect.

Cancer treatment-related neuropathic pain: proof of concept study with menthol--a TRPM8 agonist

PURPOSE

Effective treatment of neuropathic pain without unacceptable side effects is challenging. Cancer sufferers increasingly live with long-term treatment-related neuropathic pain, resulting from chemotherapy-induced peripheral neuropathy (CIPN) or surgical scars. This proof-of-concept study aimed to determine whether preclinical evidence for TRPM8 ion channels in sensory neurons as a novel analgesic target could be translated to clinical benefit in patients with neuropathic pain, using the TRPM8 activator menthol.

PATIENTS AND METHODS

Patients with problematic treatment-related neuropathic pain underwent a baseline assessment using validated questionnaires, psychophysical testing, and objective functional measures. The painful area was treated with topical 1 % menthol cream twice daily. Assessments were repeated at 4-6 weeks. The primary outcome was the change in Brief Pain Inventory total scores at 4-6 weeks. Secondary outcomes included changes in function, mood and skin sensation.

RESULTS

Fifty-one patients (female/male, 32/19) were recruited with a median age of 61 (ranging from 20 to 89). The commonest aetiology was CIPN (35/51), followed by scar pain (10/51). Thirty-eight were evaluable on the primary outcome. Eighty-two per cent (31/38) had an improvement in total Brief Pain Inventory scores (median, 47 (interquartile range, 30 to 64) to 34 (6 to 59), P < 0.001). Improvements in mood (P = 0.0004), catastrophising (P = 0.001), walking ability (P = 0.008) and sensation (P < 0.01) were also observed.

CONCLUSION

This proof-of-concept study indicates that topical menthol has potential as a novel analgesic therapy for cancer treatment-related neuropathic pain. Improvements in patient-rated measures are supported by changes in objective measures of physical function and sensation. Further systematic evaluation of efficacy is required.

Reduced sleep, stress responsivity, and female sex contribute to persistent inflammation-induced mechanical hypersensitivity in rats

Studies in humans suggest that female sex, reduced sleep opportunities and biological stress responsivity increase risk for developing persistent pain conditions. To investigate the relative contribution of these three factors to persistent pain, we employed the Sciatic Inflammatory Neuritis (SIN) model of repeated left sciatic perineurial exposures to zymosan, an inflammatory stimulus, to determine their impact upon the development of persistent mechanical hypersensitivity. Following an initial moderate insult, a very low zymosan dose was infused daily for eight days to model a sub-threshold inflammatory perturbation to which only susceptible animals would manifest or maintain mechanical hypersensitivity. Using Sprague Dawley rats, maintaining wakefulness throughout the first one-half of the 12-h light phase resulted in a bilateral reduction in paw withdrawal thresholds (PWTs); zymosan infusion reduced ipsilateral PWTs in all animals and contralateral PWTs only in females. This sex difference was validated in Fischer 344, Lewis and Sprague Dawley rats, suggesting that females are the more susceptible phenotype for both local and centrally driven responses to repeated low-level inflammatory perturbations. Hypothalamic-pituitary-adrenal (HPA) axis hyporesponsive Lewis rats exhibited the most robust development of mechanical hypersensitivity and HPA axis hyperresponsive Fischer 344 rats matched the Lewis rats' mechanical hypersensitivity throughout the latter four days of the protocol. If HPA axis phenotype does indeed influence these findings, the more balanced responsivity of Sprague Dawley rats would seem to promote resilience in this paradigm. Taken together, these findings are consistent with what is known regarding persistent pain development in humans.

Recovery sleep does not mitigate the effects of prior sleep loss on paclitaxel-induced mechanical hypersensitivity in Sprague-Dawley rats

Society has a rapidly growing accumulative sleep debt due to employment obligations and lifestyle choices that limit sleep opportunities. The degree to which poor sleep may set the stage for adverse symptom outcomes among more than 1.7 million persons who will be diagnosed with cancer is not entirely understood. Paclitaxel (PAC), a commonly used chemotherapy agent, is associated with painful, debilitating peripheral neuropathy of the hands and feet, which may persist long after adjuvant therapy is completed. The aims of this preclinical study were to determine the accumulative and sustained effects of sleep restriction on PAC-induced mechanical sensitivity in animals and whether there are male-female differences in mechanical sensitivity in PAC-injected animals. Sixty-two adult Sprague-Dawley rats (n = 31 females) were assigned to three cycles of intraperitoneal injections of PAC (1 mg/kg) versus vehicle (VEH; 1 ml/kg) every other day at light onset for 7 days, followed by seven drug-free days and to sleep restriction versus unperturbed sleep. Sleep restriction involved gentle handling to maintain wakefulness during the first 6 hr of lights on immediately following an injection; otherwise, sleep was unperturbed. Mechanical sensitivity was assessed via von Frey filaments, using the up-down method. Mechanical sensitivity data were Log10 transformed to meet the assumption of normality for repeated measures analysis of variance. Chronic sleep restriction of the PAC-injected animals resulted in significantly increased mechanical sensitivity that progressively worsened despite sleep recovery opportunities. If these relationships hold in humans, targeted sleep interventions employed during a PAC protocol may improve pain outcomes.

Chronic pain prevalence and associated factors in a segment of the population of São Paulo City

A cross-sectional epidemiologic survey was performed to determine the prevalence of chronic pain (CP) and to identify associated factors in a random sample of persons 15 years or older from a segment of the population of São Paulo City, Brazil. A total of 1,108 eligible participants were randomly selected, and face-to-face interviews were performed with 826 individuals (74.5%) between December 2011 and February 2012. Chronic Pain Grade, Hospital Anxiety and Depression Scale, and EuroQol-5D were used to verify pain characteristics and the associated signs of psychological distress. A prevalence of 42% (95% confidence interval, 38.6-45.4) was observed for CP, and the participants with CP had an average pain intensity of 5.9 (standard deviation = 1.9) and a pain-related disability of 4.1 (standard deviation = 3.2) on a 0 to 10 scale. Persistent pain was present in 68.6% of those with CP, and 32.8% of the population sample had high-intensity or high-interference pain (Chronic Pain Grade II, III, and IV). Quality of life was significantly worse among the CP individuals. The following factors were independently associated with CP: female gender, age 30 years or older, ≤ 4 years of education, symptoms consistent with anxiety, and intense physical strain. Indicators of pain severity increased with pain grades.

PERSPECTIVE

CP is highly prevalent in the city of São Paulo and has a considerable impact on health-related quality of life. Demographic, socioeconomic, and psychological factors are independently associated with this condition.

Prevalence and long-term predictors of persistent chronic widespread pain in the general population in an 11-year prospective study: the HUNT study

BACKGROUND

Chronic widespread pain (CWP) is common and associated with prominent negative consequences. The aim of this study was to assess the prevalence of persistent CWP in an 11-year prospective cohort study in the general population, and to examine anxiety, depression, alcohol use, poor sleep, body mass index (BMI) and chronic disease, along with demographic, lifestyle and other health-related variables as possible predictors for the assumed CWP persistence.

METHODS

CWP was defined as having pain at three or more predefined sites (involving the trunk and upper and lower limbs) for at least three months in the last year. We used a Norwegian general population cohort of 28,367 individuals who responded to both the second (1995-1997) and the third (2006-2008) waves of the Nord-Trøndelag Health Study (HUNT2 and HUNT3, respectively). Data were analysed with logistic regression models.

RESULTS

CWP prevalence in HUNT2 was 17%. Of those reporting CWP in HUNT2, 53% still reported CWP at follow-up in HUNT3. Adjusted analyses revealed that depression and alcohol consumption were not substantially associated with the 11-year prospective CWP outcome. Poor sleep, obesity and chronic disease predicted persistent CWP, and being male and/or 60 years or older was protective.

CONCLUSIONS

This cohort study revealed that nearly half of the participants with baseline CWP resolved from CWP 11 years later. Among those whose CWP did not resolve, obesity, sleeping problems and chronic disease predicted CWP persistence, while aging and male sex was protective. Anxiety, mixed anxiety and depression, former smoking, and overweight were weakly associated, while depression, moderate exercise, and alcohol use were not associated with persistent CWP.

Widespread pain in temporomandibular disorders

SUMMARY Chronic widespread pain (CWP) represents pain involving several regions of the body. Various psychological and social risk factors such as poor general health status, sleep disturbance, fatigue and high psychological distress have been identified for the development of CWP. Numerous chronic pain conditions are comorbid, resulting in the development of CWP in many of these patients. Temporomandibular disorder is one of the most extensively studied chronic musculoskeletal pain condition in terms of its comorbidity with CWP and fibromyalgia. It has been proposed that these comorbid pain disorders share common denominators, including exposure to certain environmental events, elevated psychological distress, pain amplification and genetic predisposition. Increased awareness of CWP is important for improved diagnoses and more effective pain management. Patients with CWP can be effectively managed in multidisciplinary pain clinics.

Chronic pain epidemiology - where do lifestyle factors fit in?

Chronic pain is common and complex and has a large impact on individuals and society. Good epidemiological pain data provide key information on the use of resources (both in general practice and in specialist clinics), insight into factors that lead to or favour chronicity and the design of interventions aimed at reducing or preventing the effects of chronic pain. This review aims to highlight the important factors associated with chronic pain, including those factors which are amenable to lifestyle intervention.

Chronic pain epidemiology and its clinical relevance

Chronic pain affects ∼20% of the European population and is commoner in women, older people, and with relative deprivation. Its management in the community remains generally unsatisfactory, partly because of lack of evidence for effective interventions. Epidemiological study of chronic pain, through an understanding of its distribution and determinants, can inform the development, targeting, and evaluation of interventions in the general population. This paper reviews current knowledge of risk markers associated with chronic pain and considers how these might inform management and prevention. Risk factors include socio-demographic, clinical, psychological, and biological factors. These are relevant to our understanding of chronic pain mechanisms and the nature of, and responses to, current and future treatments.

Predictive validity of behavioural animal models for chronic pain

Rodent models of chronic pain may elucidate pathophysiological mechanisms and identify potential drug targets, but whether they predict clinical efficacy of novel compounds is controversial. Several potential analgesics have failed in clinical trials, in spite of strong animal modelling support for efficacy, but there are also examples of successful modelling. Significant differences in how methods are implemented and results are reported means that a literature-based comparison between preclinical data and clinical trials will not reveal whether a particular model is generally predictive. Limited reports on negative outcomes prevents reliable estimate of specificity of any model. Animal models tend to be validated with standard analgesics and may be biased towards tractable pain mechanisms. But preclinical publications rarely contain drug exposure data, and drugs are usually given in high doses and as a single administration, which may lead to drug distribution and exposure deviating significantly from clinical conditions. The greatest challenge for predictive modelling is, however, the heterogeneity of the target patient populations, in terms of both symptoms and pharmacology, probably reflecting differences in pathophysiology. In well-controlled clinical trials, a majority of patients shows less than 50% reduction in pain. A model that responds well to current analgesics should therefore predict efficacy only in a subset of patients within a diagnostic group. It follows that successful translation requires several models for each indication, reflecting critical pathophysiological processes, combined with data linking exposure levels with effect on target.

Chronic Pain in a Biracial Cohort of Young Women

This is a longitudinal study of a large US biracial community cohort of 732 young women - 50% African-American and 50% Caucasian - specifically investigating incidence, remission, and progression of, as well as factors associated with common chronic pains (back, head, face, chest and abdomen). The results show back, head and abdominal pains were the most common, severe and persistent pains. Facial pain, although less common and severe, was the only pain presenting significant racial differences with Caucasians having higher prevalence, incidence and persistence; incidence per 1000 person-years was 58 for Caucasians and 18 for African-Americans while remission per 1000 person-years was 107 for Caucasians and 247 for African-Americans (p<0.05). Risk factors associated with incidence (I) differed from those associated with persistence(P), perhaps due to the young age and shorter pain duration in this population. Face pain incidence, but not persistence for example, was associated with student status, fatigue, perceived stress and general health. Depression does not seem to be associated with any of these pains. However, increased number of existing pain sites was related to subsequent increase chance of developing new pain (I) or maintaining the existing pain (P).

A different kind of co-morbidity: Understanding posttraumatic stress disorder and chronic pain

Many traumatic events leave lingering physical injuries and chronic pain in their wake, in addition to trauma-related psychopathology. In this review, we provide an overview of developments in the recent literature on co-morbid posttraumatic stress disorder (PTSD) and chronic pain. Starting with the conceptual models presented by Sharp and Harvey (2001) and Asmundson, Coons, Taylor, and Klatz (2002), this review summarizes newer studies that examine prevalence of these co-morbid conditions. Additionally, we present an updated synthesis of research on factors that may maintain both chronic physical pain and PTSD in trauma survivors. Consideration of the impact of this co-morbidity on psychosocial assessment and treatment also is discussed, with particular attention to issues that warrant additional research.

The Italian version of the Sickness Impact Profile-Roland Scale for chronic pain: cross-cultural adaptation, reliability, validity and sensitivity to change

PURPOSE

As no adapted form of the 23-item Sickness Impact Profile (SIP)-Roland Scale for patients with chronic pain has ever been validated in the Italian population, the aim of this study was to translate, culturally adapt and validate an Italian version.

METHODS

The development of the Italian version involved translation and back-translation, a final review by an expert committee and the testing of the pre-final version to establish its correspondence with the original. The psychometric testing included testing reliability by internal consistency (Cronbach's α) and test-retest repeatability (intraclass coefficient correlation; ICC), construct validity by comparison with an 11-point pain intensity numerical rating scale (NRS; Pearson's correlation) and the Short Form Health Survey (SF-36; Pearson's correlation) and sensitivity to change by calculating the minimum detectable change (MDC).

RESULTS

It took 3 months to obtain a shared version of the scale, which was administered to 243 subjects and proved to be satisfactorily acceptable. It had a high degree of internal consistency (α = 0.860) and test-retest reliability (ICC = 0.972). Construct validity testing revealed a moderate correlation with the NRS (r = 0.418), close correlations with the SF-36 physical subscales and moderate-poor correlations with the mental and social subscales; the MDC was 2.33.

CONCLUSIONS

The SIP-Roland scale was successfully translated into Italian, showing satisfactory psychometric properties. The measure can be recommended for use in research and clinical practice to improve the assessment of physical dysfunction in subjects with chronic pain.