Patients and healthcare professionals perspectives on creating a chronic pain support line in Portugal: A qualitative study protocol.

Chronic pain affects almost 38% of the Portuguese adult population, with high costs for both patients and society. Those who suffer with chronic pain frequently complain of feeling misunderstood and of lack of support. These complaints are the main reason why support telephone lines for chronic pain were created in some countries. However, there is no scientific data supporting their creation or evaluating their performance. This paper presents a qualitative study protocol to assess patients and healthcare professionals' perspectives on the creation of a telephone support line for chronic pain. It constitutes the first step to attain the main goal of developing and implementing a functioning support line for chronic pain in Portugal. The methodology to assess patients and healthcare professionals' perspectives and needs is presented. In order to gather information as close to reality as possible, focus groups interviews were chosen as data sources. Given the present context of the COVID-19 pandemic, meetings will take place online, using a digital platform. All interviews will be transcribed verbatim, coded and synthesised into categories and main themes. Thematic analysis will be conducted using NVivo® V12 software, employing an iterative and reflexive approach. Finally, comparative and relational analysis will be performed in order to identify topics where patients and professionals converge or greatly diverge. The findings will be useful for grounding the creation of a telephone support line for chronic pain patients. Results dissemination will be important for policy-makers to develop a new perspective towards chronic pain services available.

Pain as the fifth vital sign-A comparison between public and private healthcare systems.

BACKGROUND: The assessment of pain as the fifth vital sign (P5VS) is of paramount importance since it leads to the management of undertreated pain, consequently reducing suffering, readmissions and emergency department visits after hospital discharge. OBJECTIVE: To evaluate the implementation of P5VS in public and private hospitals. METHODS: Data analysis on validated questionnaires was sent to all 171 Portuguese hospitals via an official letter. RESULTS: When compared to private hospitals, public hospitals presented a higher adherence to the process related to the P5VS. It has demonstrated superiority in the charts properly placed to record P5VS, in the number of emergency departments recording P5VS, in the regularity of audits, and in the existence of guidelines and staff training on pain assessment and management. CONCLUSION: The standardization of both evaluation and recording of pain intensity constitutes a measure of good clinical practice. Public hospitals demonstrated better commitment to these procedures that should be properly carried out in all health care institutions.

TLR4 Antagonism Reduces Movement-Induced Nociception and ATF-3 Expression in Experimental Osteoarthritis.

INTRODUCTION: Toll-like receptor 4 (TLR4) is a pattern recognition receptor involved in the detection of pathogen-associated molecular patterns (PAMPs), but also a "danger-sensing" receptor that recognizes host-derived endogenous molecules called damage-associated molecular patterns (DAMPs). The involvement of TLR4 in rheumatic diseases is becoming evident, as well as its potential role as a target for therapeutic intervention. Moreover, increasing evidence also suggests that TLR4 is implicated in chronic pain states. Thus, in this study, we evaluated whether a systemic administration of a synthetic antagonist of TLR4 (TLR4-A1) could decrease nociception and cartilage degradation in experimental osteoarthritis (OA). Furthermore, as the activation transcription factor (ATF)-3 serves as a negative regulator for TLR4-stimulated inflammatory response, we also evaluated the effect of TLR4 inhibition on ATF-3 expression in primary afferent neurons at the dorsal root ganglia (DRG). METHODS: OA was induced in adult male Wistar rats through an intra-articular injection of 2 mg of sodium mono-iodoacetate (MIA) into the left knee. From days 14 to 28 after OA induction, animals received an intraperitoneal injection of either TLR4-A1 (10 mg/kg) or vehicle. Movement- and loading-induced nociception was evaluated in all animals, by the Knee-Bend and CatWalk tests, before and at several time-points after TLR4-A1/vehicle administration. Immunofluorescence for TLR4 and ATF-3 was performed in L3-L5 DRG. Knee joints were processed for histopathological evaluation. RESULTS: Administration of TLR4-A1 markedly reduced movement-induced nociception in OA animals, particularly in the Knee-Bend test. Moreover, the increase of ATF-3 expression observed in DRG of OA animals was significantly reduced by TLR4-A1. However, no effect was observed in cartilage loss nor in the neuronal cytoplasmic expression of TLR4 upon antagonist administration. CONCLUSION: The TLR4 antagonist administration possibly interrupts the TLR4 signalling cascade, thus decreasing the neurotoxic environment at the joint, which leads to a reduction in ATF-3 expression and in nociception associated with experimental OA.

Amylin, a peptide expressed by nociceptors, modulates chronic neuropathic pain.

BACKGROUND: Amylin is a calcitonin gene-related peptide family member expressed by nociceptors. Amylin's expression is down-regulated following nerve damage, and studies suggested it affects nociception. We aimed at clarifying amylin's effects on chronic neuropathic pain and investigating its site of action. METHODS: Chronic neuropathic pain was induced in rats by spared nerve injury (SNI) surgery. Mechanical allodynia/hyperalgesia and cold allodynia/hyperalgesia were assessed by the von Frey, pinprick, acetone and cold plate behavioural tests, respectively. Amylin, amylin-receptor antagonist (AC187) or vehicle solutions were delivered chronically, by a subcutaneous (SC) mini-osmotic pump, or acutely, by SC or intrathecal (IT) injections. Cellular and fibre markers were used to detect spinal cord alterations in SNI rats after chronic amylin administration. RESULTS: Continuous subcutaneous amylin administration aggravated cold allodynia in SNI animals, possibly via amylin-receptors (AmyR) in supraspinal areas. Acute intrathecal administration of amylin attenuated mechanical hyperalgesia, whereas AC187 reduced mechanical allodynia, suggesting distinct roles of endogenous amylin and of pharmacological amylin doses when targeting spinal cord amylin receptors. Chronic amylin administration promoted c-Fos activation only in the dorsal horn neurons of SHAM animals, suggesting a distinctive role of amylin in the activation of the spinal neuronal circuitry under neuropathic and physiological conditions. ERK1/2 phosphorylation increased in the dorsal horn neurons of SNI rats chronically treated with amylin. This ERK1/2 cascade activation may be related to amylin's effect on the aggravation of cold allodynia in SNI rats. CONCLUSIONS: Amylin's nociceptive effects seem to depend on the treatment duration and route of administration by acting at different levels of the nervous system. SIGNIFICANCE: Amylin modulated neuropathic pain by acting at different levels of the nervous system. Whereas supraspinal areas may be involved in amylin's induced pronociception, modulation of spinal cord amylin receptors by endogenous or pharmacological amylin doses triggers both pro- and antinociceptive effects.

Lung cancer: a brief review of epidemiology and screening.

The global burden of lung cancer has been increasing over the past years, and is still a major threat to public health worldwide, leading to disabilities and premature mortality. Despite multifactorial cause, smoking remains as the major etiological factor, followed by occupational exposure to carcinogens, genetic predisposition and other concomitant diseases. In order to reduce the individual and social burden due to the direct and indirect costs related to the lung cancer treatment, accurate methods of screening are needed. Among those, x-ray with cytological analysis of sputum was first proposed. Nowadays, more sensitive methods such as low-dose computed tomography are being used to improve the early detection. In the future, molecular biomarkers may complement low-dose computed tomography and improve the robustness of early lung cancer detection.

Drug-Induced HSP90 Inhibition Alleviates Pain in Monoarthritic Rats and Alters the Expression of New Putative Pain Players at the DRG.

Purinergic receptors (P2XRs) have been widely associated with pain states mostly due to their involvement in neuron-glia communication. Interestingly, we have previously shown that satellite glial cells (SGC), surrounding dorsal root ganglia (DRG) neurons, become activated and proliferate during monoarthritis (MA) in the rat. Here, we demonstrate that P2X7R expression increases in ipsilateral DRG after 1 week of disease, while P2X3R immunoreactivity decreases. We have also reported a significant induction of the activating transcriptional factor 3 (ATF3) in MA. In this study, we show that ATF3 knocked down in DRG cell cultures does not affect the expression of P2X7R, P2X3R, or glial fibrillary acidic protein (GFAP). We suggest that P2X7R negatively regulates P2X3R, which, however, is unlikely mediated by ATF3. Interestingly, we found that ATF3 knockdown in vitro induced significant decreases in the heat shock protein 90 (HSP90) expression. Thus, we evaluated in vivo the involvement of HSP90 in MA and demonstrated that the HSP90 messenger RNA levels increase in ipsilateral DRG of inflamed animals. We also show that HSP90 is mostly found in a cleaved form in this condition. Moreover, administration of a HSP90 inhibitor, 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG), attenuated MA-induced mechanical allodynia in the first hours. The drug also reversed the HSP90 upregulation and cleavage. 17-DMAG seemed to attenuate glial activation and neuronal sensitization (as inferred by downregulation of GFAP and P2X3R in ipsilateral DRG) which might correlate with the observed pain alleviation. Our data indicate a role of HSP90 in MA pathophysiology, but further investigation is necessary to clarify the underlying mechanisms.

Interventional Pain Management in Multidisciplinary Chronic Pain Clinics: A Prospective Multicenter Cohort Study with One-Year Follow-Up.

BACKGROUND: Interventional Pain Management (IPM) is performed in multidisciplinary chronic pain clinics (MCPC), including a range of invasive techniques to diagnose and treat chronic pain (CP) conditions. Current patterns of use of those techniques in MCPC have not yet been reported. OBJECTIVE: We aimed to describe quantitatively and qualitatively the use of IPM and other therapeutic procedures performed on-site at four Portuguese MCPC. METHODS: A prospective cohort study with one-year follow-up was performed in adult patients. A structured case report form was systematically completed at baseline and six and 12 months. RESULTS: Among 808 patients referred to the MCPC, 17.2% had been prescribed IPM. Patients with IPM were on average younger and had longer CP duration and lower levels of maximum pain and pain interference/disability. The three main diagnoses were low back pain (n = 28), postoperative CP, and knee pain (n = 16 each). From 195 IPM prescribed, nerve blocks (n = 108), radiofrequency (n = 31), and viscosupplementation (n = 22) were the most prevalent. Some IPM techniques were only available in few MCPC. One MCPC did not provide IPM. CONCLUSIONS: IPM are seldom prescribed in Portuguese MCPC. Further studies on IPM safety and effectiveness are necessary for clear understanding the role of these techniques in CP management.

Persistent postoperative pain after cardiac surgery: a systematic review with meta-analysis regarding incidence and pain intensity.

Persistent postoperative pain (PPP) has been described as a complication of cardiac surgery (CS). We aimed to study PPP after CS (PPPCS) by conducting a systematic review of the literature regarding its incidence, intensity, location, and the presence of neuropathic pain, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. The review comprised 3 phases: a methodological assessment of 6 different databases identifying potential articles and screening for inclusion criteria by 2 independent reviewers; data extraction; and study quality assessment. Meta-analysis was used to estimate the pooled incidence rates using a random effects model. We have identified 442 potentially relevant studies through database searching. A total of 23 studies (involving 11,057 patients) met our inclusion criteria. Persistent postoperative pain affects 37% patients in the first 6 months after CS, and it remains present more than 2 years after CS in 17%. The reported incidence of PPP during the first 6 months after CS increased in recent years. Globally, approximately half of the patients with PPPCS reported moderate to severe pain. Chest is the main location of PPPCS followed by the leg; neuropathic pain is present in the majority of the patients. This is the first systematic review and meta-analysis to provide estimates regarding incidence and intensity of PPPCS, which elucidates its relevance. There is an urgent need for adequate treatment and follow-up in patients with PPPCS.

Portuguese Version of the Pain Beliefs and Perceptions Inventory: A Multicenter Validation Study.

BACKGROUND: We aimed to perform the translation, cultural adaptation, and validation of the Pain Beliefs and Perceptions Inventory (PBPI) for the European Portuguese language and chronic pain population. METHODS: This is a longitudinal multicenter validation study. A Portuguese version of the PBPI (PBPI-P) was created through a process of translation, back translation, and expert panel evaluation. The PBPI-P was administered to a total of 122 patients from 13 chronic pain clinics in Portugal, at baseline and after 7 days. Internal consistency and test-retest reliability were assessed by Cronbach's alpha (α) and intraclass correlation coefficient (ICC). Construct (convergent and discriminant) validity was assessed based on a set of previously developed theoretical hypotheses about interrelations between the PBPI-P and other measures. Exploratory and confirmatory factor analyses were performed to test the theoretical structure of the PBPI-P. RESULTS: The internal consistency and test-retest reliability coefficients for each respective subscale were α = 0.620 and ICC = 0.801 for mystery; α = 0.744 and ICC = 0.841 for permanence; α = 0.778 and ICC = 0.791 for constancy; and α = 0.764 and ICC = 0.881 for self-blame. Exploratory and confirmatory factor analysis revealed a four-factor structure (performance, constancy, self-blame, and mystery) that explained 63% of the variance. The construct validity of the PBPI-P was shown to be adequate, with more than 90% of the previously defined hypotheses regarding interrelations with other measures confirmed. CONCLUSION: The PBPI-P has been shown to be adequate and to have excellent reliability, internal consistency, and validity. It may contribute to a better pain assessment and is suitable for research and clinical use.

Reliability and validity of the Bowel Function Index for evaluating opioid-induced constipation: translation, cultural adaptation and validation of the Portuguese version (BFI-P).

OBJECTIVE: The Bowel Function Index (BFI) is a simple and sound bowel function and opioid-induced constipation (OIC) screening tool. We aimed to develop the translation and cultural adaptation of this measure (BFI-P) and to assess its reliability and validity for the Portuguese language and a chronic pain population. METHODS: The BFI-P was created after a process including translation, back translation and cultural adaptation. Participants (n = 226) were recruited in a chronic pain clinic and were assessed at baseline and after one week. Internal consistency, test-retest reliability, responsiveness, construct (convergent and known groups) and factorial validity were assessed. RESULTS: Test-retest reliability had an intra-class correlation of 0.605 for BFI mean score. Internal consistency of BFI had Cronbach's alpha of 0.865. The construct validity of BFI-P was shown to be excellent and the exploratory factor analysis confirmed its unidimensional structure. The responsiveness of BFI-P was excellent, with a suggested 17-19 point and 8-12 point change in score constituting a clinically relevant change in constipation for patients with and without previous constipation, respectively. CONCLUSIONS: This study had some limitations, namely, the criterion validity of BFI-P was not directly assessed; and the absence of a direct criterion for OIC precluded the assessment of the criterion based responsiveness of BFI-P. Nevertheless, BFI may importantly contribute to better OIC screening and its Portuguese version (BFI-P) has been shown to have excellent reliability, internal consistency, validity and responsiveness. Further suggestions regarding statistically and clinically important change cut-offs for this instrument are presented.

A prospective study on the neurological complications of breast cancer and its treatment: Updated analysis three years after cancer diagnosis.

OBJECTIVES: To quantify the prevalence of neurological complications among breast cancer patients at one and three years after diagnosis, and to identify factors associated with neuropathic pain (NP) and chemotherapy-induced peripheral neuropathy (CIPN). MATERIAL AND METHODS: Prospective cohort study including 475 patients with newly diagnosed breast cancer, recruited among those proposed for surgical treatment (Portuguese Institute of Oncology, Porto). Patients underwent a neurological evaluation and had their cognitive function assesses with the Montreal Cognitive Assessment, before treatment and at one and three years after enrollment. We estimated the prevalence of each neurological complication, and odds ratios (OR), adjusted for socio-demographic and clinical characteristics, to identify factors associated with NP and CIPN. RESULTS: More than half of the patients [54.7%, 95% confidence interval (95%CI): 50.2-59.2] presented at least one neurological complication, at one or at three years after cancer diagnosis. Between the first and the third year of follow-up, there was an increase in the prevalence of NP (from 21.1% to 23.6%), cognitive impairment (from 7.2% to 8.2%), cerebrovascular disease (from 0.6% to 1.5%) and brain metastasis (from 0.0% to 0.6%). The prevalence of CIPN decreased from 14.1% to 12.6%. Axillary lymph node dissection was associated with NP at one year (OR = 2.75, 95%CI: 1.34-5.63) and chemotherapy with NP at three years (OR = 2.10, 95%CI: 1.20-3.67). Taxane-based chemotherapy was strongly associated with prevalence of CIPN at one and three years. CONCLUSION: Neurological complications are frequent even three years after cancer diagnosis and NP remained the major contributor to the burden of these conditions among survivors.

Spared nerve injury model to study orofacial pain.

BACKGROUND & OBJECTIVES: There are many difficulties in generating and testing orofacial pain in animal models. Thus, only a few and limited models that mimic the human condition are available. The aim of the present research was to develop a new model of trigeminal pain by using a spared nerve injury (SNI) surgical approach in the rat face (SNI-face). METHODS: Under anaesthesia, a small incision was made in the infraorbital region of adult male Wistar rats. Three of the main infraorbital nerve branches were tightly ligated and a 2 mm segment distal to the ligation was resected. Control rats were sham-operated by exposing the nerves. Chemical hyperalgesia was evaluated 15 days after the surgery by analyzing the time spent in face grooming activity and the number of head withdrawals in response to the orofacial formalin test. RESULTS: SNI-face rats presented a significant increase of the formalin-induced pain-related behaviours evaluated both in the acute and tonic phases (expected biphasic pattern), in comparison to sham controls. INTERPRETATION & CONCLUSIONS: The SNI-face model in the rat appears to be a valid approach to evaluate experimental trigeminal pain. Ongoing studies will test the usefulness of this model to evaluate therapeutic strategies for the treatment of orofacial pain.

Results of Lumbar Endoscopic Adhesiolysis Using a Radiofrequency Catheter in Patients with Postoperative Fibrosis and Persistent or Recurrent Symptoms After Discectomy.

OBJECTIVE: To evaluate the results of lumbar epiduroscopic adhesiolysis using mechanical methods and a radiofrequency catheter followed by epidural steroid and local anesthetic administration in patients with postoperative fibrosis and persistent or recurrent symptoms. STUDY DESIGN: Prospective study. METHODS: Patients with persistent or recurrent low back and/or lower limb pain after lumbar spine surgery, in whom no relevant findings were present on MR images besides epidural scar tissue, were submitted to epiduroscopic adhesiolysis. Patient-reported outcomes including pain and disability were assessed in predefined time intervals and compared to baseline. RESULTS: Twenty-four patients were enrolled. It was possible to elicit the patient's usual pain by probing the epidural scar tissue in all patients. Statistically significant improvement in low back and lower limb pain was observed in all assessment periods up to 12 months. A pain relief over 50% was achieved in 71% of the patients at 1 month, 63% at 3 and 6 months, and 38% at 12 months. Disability scores significantly improved for around 6 months. Mean patient satisfaction rates were 80% at 1 month, 75% at 3 months, 70% at 6 months, and 67% 1 year after intervention. Only 1 transient postprocedural complication was detected. CONCLUSION: Endoscopic adhesiolysis is a potentially useful treatment for the relief of chronic intractable low back and lower limb pain in patients with previous lumbar spine surgery and epidural fibrosis. The use of larger volumes of saline during endoscopy and the employment of radiofrequency for the lysis of epidural adhesions are safe procedures, which may provide an additional benefit to the intervention.

Neurological complications of breast cancer: A prospective cohort study.

OBJECTIVES: Neurological complications secondary to breast cancer treatment may be an important contributor to these patients morbidity. We aimed to quantify the incidence of neurological complications of breast cancer treatment during the first year after diagnosis. MATERIALS AND METHODS: We performed a prospective cohort study with 506 patients recruited at the Portuguese Institute of Oncology of Porto, among those newly diagnosed. Participants underwent a neurological examination before treatment, after surgery, after chemotherapy (whenever applicable) and at one year after enrollment. The Montreal Cognitive Assessment was used to assess cognitive function, at baseline and at one year. We computed one-year cumulative incidence estimates and the corresponding 95% confidence intervals (95%CI) for each of the neurological complications. RESULTS: Just over half of women had breast cancer stage 0 or I. A total of 6.9% were submitted to neoadjuvant chemotherapy but most of them completed adjuvant treatment - endocrine therapy, radiotherapy or chemotherapy (83.9%, 73.0% and 52.5%, respectively). The cumulative incidence of at least one oncological-related neurological complication during the first year after diagnosis was 48.4% (95%CI: 44.1-52.8); the most frequent were neuropathic pain (30.8%, 95%CI: 27.0-35.0), chemotherapy-induced peripheral neuropathy (16.8%, 95%CI: 13.8-20.3), phantom breast pain/syndrome (16.6%, 95%CI: 13.6-20.1) and cognitive decline (8.1%, 95%CI: 5.8-11.1). CONCLUSIONS: Neurological complications were a frequent side-effect of breast cancer management in the first year after diagnosis, especially neuropathic pain and chemotherapy-induced peripheral neuropathy. Accurate diagnosis and treatment of these complications are important to minimize the burden associated with breast cancer treatment in breast cancer survivors.

Satellite glial cells surrounding primary afferent neurons are activated and proliferate during monoarthritis in rats: is there a role for ATF3?

Joint inflammatory diseases are debilitating and very painful conditions that still lack effective treatments. Recently, glial cells were shown to be crucial for the development and maintenance of chronic pain, constituting novel targets for therapeutic approaches. At the periphery, the satellite glial cells (SGCs) that surround the cell bodies of primary afferents neurons in the dorsal root ganglia (DRG) display hypertrophy, proliferation, and activation following injury and/or inflammation. It has been suggested that the expression of neuronal injury factors might initially trigger these SGCs-related events. We then aimed at evaluating if SGCs are involved in the establishment/maintenance of articular inflammatory pain, by using the monoarthritis (MA) model, and if the neuronal injury marker activating transcriptional factor 3 (ATF3) is associated with these SGCs' reactive changes. Western Blot (WB) analysis of the glial fibrillary acidic protein (GFAP) expression was performed in L4-L5 DRGs from control non-inflamed rats and MA animals at different time-points of disease (4, 7, and 14d, induced by complete Freund's adjuvant injection into the left hind paw ankle joint). Data indicate that SGCs activation is occurring in MA animals, particularly after day 7 of disease evolution. Additionally, double-immunostaining for ATF3 and GFAP in L5 DRG sections shows that SGCs's activation significantly increases around stressed neurons at 7d of disease, when compared with control animals. The specific labelling of GFAP in SGCs rather than in other cell types was also confirmed by immunohistochemical labeling. Finally, BrdU incorporation indicates that proliferation of SGCs is also significantly increased after 7 days of MA. Data indicate that SGCs play an important role in the mechanisms of articular inflammation, with 7 days of disease being a critical time-point in the MA model, and suggest that ATF3 might be involved in SGCs' reactive changes such as activation.

New insights from immunohistochemistry for the characterization of epidural scar tissue.

BACKGROUND: The association between epidural fibrosis and recurrent symptoms after lumbar spine surgery remains a matter of debate in scientific literature and the underlying pathophysiological mechanism has not been clearly elucidated. OBJECTIVE: To investigate the presence of nerve fibers and the expression of osteopontin in epidural fibrous tissue after lumbar surgery in humans. STUDY DESIGN: Laboratory study of human tissue samples. METHODS: Twenty-four patients with persistent or recurrent low back and/or leg pain after lumbar spine surgery, in whom no relevant findings were present on magnetic resonance imaging (MRI) besides epidural scar tissue, were submitted to epiduroscopy. Biopsy samples of epidural scar tissue resting in the posterior epidural and periradicular space were obtained from 15 patients, using an endoscopic grasping forceps, in locations where the stimulation with the tip of a Fogarty consistently reproduced pain. Biopsy samples were processed for examination under optical and transmission electron microscopes and under a fluorescence microscope after incubation in primary antibodies against beta3-tubulin or against osteopontin. RESULTS: Optical and transmission electron microscopy revealed a homogeneous fibrous tissue rich in collagen and lacking nerve fibers. No immunofluorescence was present in any of the samples immunoreacted against beta3-tubulin. In the samples immunoreacted against osteopontin, a punctate signal was detected around the collagen fibers. LIMITATIONS: Being a human study, there was no control group, so it is not possible to determine the contribution of osteopontin in the formation of epidural fibrosis and its relation to the patients' symptoms. Additional animal studies are needed to investigate these issues. CONCLUSION: Rather than direct stimulation of nociceptors in the epidural scar tissue, other factors should relate epidural fibrosis and recurrent symptoms after lumbar spine surgery. Osteopontin seems to play a role in the formation of epidural fibrosis.

A population-based study on chronic pain and the use of opioids in Portugal.

Although increasing doubts exist regarding the long-term effectiveness and safety of opioids in patients with chronic pain (CP), most guidelines still recognize opioids as an option in effective management of CP. We aimed to describe the prevalence and factors associated with opioid use in subjects with CP in Portugal and to evaluate satisfaction and self-assessed treatment effectiveness. A nationwide study was conducted in a representative sample of the adult Portuguese population. The 5094 participants were selected using random digit dialing and estimates were adequately weighted for the population. The prevalence of opioid use by subjects with CP was 4.37% (95% confidence interval [CI] 3.4-5.5); and in subjects experiencing CP with and without cancer, it was 10.13% and 4.24%, respectively. Use of strong opioids was reported by only 0.17% of CP subjects. Sex, pain severity and symptoms of depression and anxiety were significantly associated with opioid use; however, in multivariate modeling, only pain-related disability remained significant. No significant differences among users and nonusers of opioids were observed regarding treatment satisfaction and self-assessed effectiveness. Although extremely high rates of use of opioids exist in a few countries, it should not be seen as a ubiquitous problem. Indeed, we showed that in Portugal, as in many other regions in the world, opioids are used much less frequently than in those few countries. Moreover, we did not find significant differences among users and nonusers of opioids regarding satisfaction and self-assessed effectiveness, eventually showing the results to be in line with reports that show doubt about opioids' effectiveness. Further research and particular attention to and continuous monitoring of the trends of use and abuse of opioids worldwide are recommended.

Epidemiology of chronic pain: a population-based nationwide study on its prevalence, characteristics and associated disability in Portugal.

UNLABELLED: A cross-sectional nationwide epidemiological study was performed in a random sample of the Portuguese adult population, aiming to describe the prevalence and impact of chronic pain (CP). The 5,094 participants were selected by random digit dialing, between January 2007 and March 2008, and estimates were adequately weighted for the population. Prevalence of CP was 36.7% (95% confidence interval [CI] [35.3-38.2]), based on the definition of the International Association for the Study of Pain. Recurrent or continuous pain was present in 85% of those with CP, and moderate-to-severe intensity and disability were present in 68 and 35%, respectively. Highest CP prevalence was observed among the elderly, retired, unemployed, and less educated. Highest disability was found in relation with family/home responsibilities, recreational activities, occupation/work, and sleep/rest; 13% reported a diagnosis of depression and 49% reported interference in their job. The main factors associated with disability were sex, pain intensity, and depression or depressive symptoms. CP is highly prevalent, causes high personal and social burden, and affects particularly the most vulnerable subgroups. Portugal, depending on CP definition, could be placed in the lower prevalence group in Europe. Improvement in pain intensity management and special attention to affective components of CP are recommended. PERSPECTIVE: In this cross-sectional nationwide epidemiological study, we showed that chronic pain is a significant problem that is present in 37% of the Portuguese adult general population, is associated with high personal, family, and social burden, and affects in particular the most vulnerable subgroups of the population.

Dose-dependent expression of neuronal injury markers during experimental osteoarthritis induced by monoiodoacetate in the rat.

BACKGROUND: It was recently reported that the mono-iodoacetate (MIA) experimental model of osteoarthritis (OA) courses with changes of neurons innervating the affected joints that are commonly interpreted as a neuronal response to axonal injury. To better characterize these changes, we evaluated the expression of two markers of neuronal damage, ATF-3 and NPY, and the growth associated protein GAP-43, in primary afferent neurons of OA animals injected with three different doses of MIA (0.3, 1 or 2 mg). Measurements were performed at days 3, 7, 14, 21 and 31 post-MIA injection. RESULTS: OA animals showed the characteristic histopathological changes of the joints and the accompanying nociceptive behaviour, evaluated by the Knee-Bed and CatWalk tests. An increase of ATF-3 expression was detected in the DRG of OA animals as early as 3 days after the injection of 1 or 2 mg of MIA and 7 days after the injection of 0.3 mg. NPY expression was increased in animals injected with 1 or 2 mg of MIA, at day 3 or in all time-points, respectively. From day 7 onwards there was a massive increase of GAP-43 expression in ATF-3 cells. CONCLUSIONS: The expression of the neuronal injury markers ATF-3 and NPY as well as an up-regulation of GAP-43 expression, indicative of peripheral fibre regeneration, suggests that axonal injury and a regeneration response may be happening in this model of OA. This opens new perspectives in the unravelling of the physiopathology of the human disease.