C-reactive protein and cold-pressor tolerance in the general population: the Tromsø Study

The impact of different music genres on pain tolerance: emphasizing the significance of individual music genre preferences

Music is a promising (adjunctive) treatment for both acute and chronic pain, reducing the need for pharmacological analgesics and their side effects. Yet, little is known about the effect of different types of music. Hence, we investigated the efficacy of five music genres (Urban, Electronic, Classical, Rock and Pop) on pain tolerance. In this parallel randomized experimental study, we conducted a cold pressor test in healthy volunteers (n = 548). The primary outcome was pain tolerance, measured in seconds. No objective (tolerance time) or subjective (pain intensity and unpleasantness) differences were found among the five genres. Multinomial logistic regression showed that overall genre preference positively influenced pain tolerance. In contrast, the music genres that participants thought would help for pain relief did not. Our study was the first to investigate pain tolerance at genre level and in the context of genre preference without self-selecting music. In conclusion, this study provides evidence that listening to a favored music genre has a significant positive influence on pain tolerance, irrespective of the kind of genre. Our results emphasize the importance of individual music (genre) preference when looking at the analgesic benefits of music. This should be considered when implementing music in the clinical setting.

Association between pro-inflammatory diet and abdominal pain: cross-sectional and case-control study from UK biobank and NHANES 2017-2020

BACKGROUND

There is a close association between diet and abdominal pain; however, relationship between inflammatory diet and characteristics of abdominal pain has not been characterized yet.

METHODS

This study analyzed baseline data from the UK Biobank, 3-item DHQ-Abdominal Pain Questionnaire (DHQ-3Q), which including abdominal pain in the past 3 months, severity of abdominal pain, and frequency of abdominal pain, and data from the National Health and Nutrition Examination Survey (NHANES) from 2017 to 2020. Energy-adjusted Dietary Inflammatory Index (E-DII), constructed based on 26 or 27 nutrients, was analyzed using continuous or categorical methods. Logistic regression and restricted cubic spline analyses examined the association between E-DII and abdominal pain.

RESULTS

In UK Biobank, compared to participants in the lowest quintile of E-DII, the adjusted ORs for the highest quintile were 1.12 (95% CI 1.02-1.24; P = .022), 1.05 (95% CI 1.00-1.09; P = .030), 1.26 (95% CI 1.17-1.36; P < .001), and 1.10 (95% CI 1.00-1.20; P = .044) for chronic abdominal pain, abdominal pain in the past three months, severity of abdominal pain, and frequency of abdominal pain, respectively. In NHANES, compared to participants in the lowest quintile of E-DII, the adjusted ORs for the highest quintile were 1.46 (95% CI 1.20-1.77;P < .001), 1.75 (95% CI 1.20-2.60; P = .005), 1.45 (95% CI 1.14-1.87; P = .003), and 1.18 (95% CI 0.82-1.72; P = .380) for abdominal pain in the past year, upper left abdominal pain, upper middle abdominal pain, and upper right abdominal pain. Additionally, there was a nonlinear correlation between E-DII score and DHQ-3Q (P nonlinear <.001).

CONCLUSION

Following a pro-inflammatory diet is linked to a higher likelihood of experiencing abdominal pain, as well as increased severity and frequency of such pain. Therefore, further longitudinal studies are necessary to investigate this relationship.

Periodontitis is associated with decreased experimental pressure pain tolerance: The Tromsø Study 2015-2016

AIM

To assess the relationship between periodontitis and experimental pain tolerance.

MATERIALS AND METHODS

Participants from the population-based seventh survey of the Tromsø Study with data on periodontitis were included (n = 3666, 40-84 years old, 51.6% women). Pain tolerance was assessed through (i) pressure pain tolerance (PPT) test with a computerized cuff pressure algometry on the leg, and (ii) cold-pressor tolerance (CPT) test where one hand was placed in circulating 3°C water. Cox proportional hazard regression was used to assess the association between periodontitis and pain tolerance adjusted for age, sex, education, smoking and obesity.

RESULTS

In the fully adjusted model using the 2012 Centers for Disease Control/American Academy of Periodntology case definitions for surveillance of periodontitis, moderate (hazard ratio [HR] = 1.09; 95% confidence interval [CI]: 1.01, 1.18) and severe (HR = 1.25, 95% CI: 1.11, 1.42) periodontitis were associated with decreased PPT. Using the 2018 classification of periodontitis, having Stage II/III/IV periodontitis was significantly associated with decreased PPT (HR = 1.09; 95% CI: 1.01, 1.18) compared with having no or stage I periodontitis. There were no significant associations between periodontitis and CPT in fully adjusted models.

CONCLUSIONS

Moderate and severe periodontitis was associated with experimental PPT.

Pain mechanisms in the transgender individual: a review

Specific Aim

Provide an overview of the literature addressing major areas pertinent to pain in transgender persons and to identify areas of primary relevance for future research.

Methods

A team of scholars that have previously published on different areas of related research met periodically though zoom conferencing between April 2021 and February 2023 to discuss relevant literature with the goal of providing an overview on the incidence, phenotype, and mechanisms of pain in transgender patients. Review sections were written after gathering information from systematic literature searches of published or publicly available electronic literature to be compiled for publication as part of a topical series on gender and pain in the Frontiers in Pain Research.

Results

While transgender individuals represent a significant and increasingly visible component of the population, many researchers and clinicians are not well informed about the diversity in gender identity, physiology, hormonal status, and gender-affirming medical procedures utilized by transgender and other gender diverse patients. Transgender and cisgender people present with many of the same medical concerns, but research and treatment of these medical needs must reflect an appreciation of how differences in sex, gender, gender-affirming medical procedures, and minoritized status impact pain.

Conclusions

While significant advances have occurred in our appreciation of pain, the review indicates the need to support more targeted research on treatment and prevention of pain in transgender individuals. This is particularly relevant both for gender-affirming medical interventions and related medical care. Of particular importance is the need for large long-term follow-up studies to ascertain best practices for such procedures. A multi-disciplinary approach with personalized interventions is of particular importance to move forward.

Altered somatosensory functioning and mechanism-based classification in breast cancer patients with persistent pain

Pain is one of the most frequent and persistent side effects of breast cancer treatment. Besides pain, breast cancer survivors (BCS) are prone to experience a myriad of other signs and symptoms related to altered somatosensory function, including for example, hypoesthesia, allodynia, and hyperalgesia, both at the local site of cancer and in remote body parts. Different breast cancer treatments can have a direct effect on somatosensory functioning, resulting in a wide range of these signs and symptoms. To our knowledge, currently no comprehensive overview exists on altered somatosensory functioning and resulting signs and symptoms in BCS with persistent pain. Investigating altered somatosensory functioning in this population could provide more insights in the underpinning pathophysiological mechanisms and consequently improve prevention and treatment in the future. Therefore, in this paper, first, normal somatosensory functioning is described. Second, quantitative sensory testing is presented as the recommend method to evaluate somatosensory functioning. Third, existing evidence on altered somatosensory functioning in BCS with persistent pain is summarized. Altered somatosensory functioning related to the most common cancer treatment modalities, including surgery and radiotherapy, hormone therapy, and chemotherapy are discussed. In addition, evidence on the presence of nociplastic pain as pain resulting from altered somatosensory functioning without evidence for nociception and/or neuropathy in BCS is summarized. At last, a discussion on this available evidence, limitations, and perspectives for clinical practice and for research are made.

Low-carbohydrate and ketogenic diets: a scoping review of neurological and inflammatory outcomes in human studies and their relevance to chronic pain

Dietary restriction of carbohydrate has been demonstrated to be beneficial for nervous system dysfunction in animal models and may be beneficial for human chronic pain. The purpose of this review is to assess the impact of a low-carbohydrate/ketogenic diet on the adult nervous system function and inflammatory biomarkers to inform nutritional research for chronic pain. An electronic database search was carried out in May 2021. Publications were screened for prospective research with dietary carbohydrate intake <130 g per day and duration of ≥2 weeks. Studies were categorised into those reporting adult neurological outcomes to be extracted for analysis and those reporting other adult research outcomes. Both groups were screened again for reported inflammatory biomarkers. From 1548 studies, there were 847 studies included. Sixty-four reported neurological outcomes with 83% showing improvement. Five hundred and twenty-three studies had a different research focus (metabolic n = 394, sport/performance n = 51, cancer n = 33, general n = 30, neurological with non-neuro outcomes n = 12, or gastrointestinal n = 4). The second screen identified sixty-three studies reporting on inflammatory biomarkers, with 71% reporting a reduction in inflammation. The overall results suggest a favourable outcome on the nervous system and inflammatory biomarkers from a reduction in dietary carbohydrates. Both nervous system sensitisation and inflammation occur in chronic pain, and the results from this review indicate it may be improved by low-carbohydrate nutritional therapy. More clinical trials within this population are required to build on the few human trials that have been done.

Are We Any Closer to Understanding How Chronic Pain Develops? A Systematic Search and Critical Narrative Review of Existing Chronic Pain Vulnerability Models

Identifying biopsychosocial factors underlying chronic pain vulnerability is essential for the design of preventative efforts. Multiple chronic pain vulnerability models exist, however, there is a lack of comprehensive evaluation of these models in the literature, potentially due to the lack of guidelines that specify the criteria by which these types of work should be assessed. In this work, we created evaluation criteria (based on the general goals of conceptual models), and we then used them to critically review the chronic pain vulnerability models available in the current peer-reviewed literature (identified through a systematic search). Particularly, we evaluated the models on the basis of conceptual clarity/specificity of measures, depth of description of aetiological and mechanistic factors, use of a whole system approach, and quality of the evidence associated with the models. We found nine conceptual models that have been explored in detail (eg, fear avoidance model, diathesis-stress model). These models excel at clarity and are supported mostly by self-report evidence of a psychological nature (anxiety sensitivity, pain catastrophizing, etc.), but provide little explanation of mechanistic and aetiological factors. In the future, models could be improved by complementing them with proposals from other models and exploring potential causal factors and mechanisms maintaining the condition. This task could be carried out through prospective cohort studies, and computational approaches, amongst others.

Stimulated whole-blood cytokine/chemokine responses are associated with interstitial cystitis/bladder pain syndrome phenotypes and features of nociplastic pain: a multidisciplinary approach to the study of chronic pelvic pain research network study

ABSTRACT

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a common and debilitating disease with poor treatment outcomes. Studies from the multidisciplinary approach to the study of chronic pelvic pain research network established that IC/BPS patients with chronic overlapping pain conditions (COPCs) experience poorer quality of life and more severe symptoms, yet the neurobiological correlates of this subtype are largely unknown. We previously showed that ex vivo toll-like receptor 4 (TLR4) cytokine/chemokine release is associated with the presence of COPCs, as well as widespread pain and experimental pain sensitivity women with IC/BPS. Here, we attempt to confirm these findings in the multisite multidisciplinary approach to the study of chronic pelvic pain Symptom Patterns Study using TLR4-stimulated whole blood (female IC/BPS patients with COPC n = 99; without n = 36). Samples were collected in tubes preloaded with TLR4 agonist, incubated for 24 hours, and resulting supernatant assayed for 7 cytokines/chemokines. These were subject to a principal components analysis and the resulting components used as dependent variables in general linear models. Controlling for patient age, body mass index, and site of collection, we found that greater ex vivo TLR4-stimulated cytokine/chemokine release was associated with the presence of COPCs ( P < 0.01), extent of widespread pain ( P < 0.05), but not experimental pain sensitivity ( P > 0.05). However, a second component of anti-inflammatory, regulatory, and chemotactic activity was associated with reduced pain sensitivity ( P < 0.01). These results confirm that the IC/BPS + COPCs subtype show higher levels of ex vivo TLR4 cytokine/chemokine release and support a link between immune priming and nociplastic pain in IC/BPS.

Immunometabolic rewiring in long COVID patients with chronic headache

Almost 20% of patients with COVID-19 experience long-term effects, known as post-COVID condition or long COVID. Among many lingering neurologic symptoms, chronic headache is the most common. Despite this health concern, the etiology of long COVID headache is still not well characterized. Here, we present a longitudinal multi-omics analysis of blood leukocyte transcriptomics, plasma proteomics and metabolomics of long COVID patients with chronic headache. Long COVID patients experienced a state of hyper-inflammation prior to chronic headache onset and maintained persistent inflammatory activation throughout the progression of chronic headache. Metabolomic analysis also revealed augmented arginine and lipid metabolisms, skewing towards a nitric oxide-based pro-inflammation. Furthermore, metabolisms of neurotransmitters including serotonin, dopamine, glutamate, and GABA were markedly dysregulated during the progression of long COVID headache. Overall, these findings illustrate the immuno-metabolomics landscape of long COVID patients with chronic headache, which may provide insights to potential therapeutic interventions.

Inflammatory Blood Signature Related to Common Psychological Comorbidity in Chronic Pain

Chronic pain is characterized by high psychological comorbidity, and diagnoses are symptom-based due to a lack of clear pathophysiological factors and valid biomarkers. We investigate if inflammatory blood biomarker signatures are associated with pain intensity and psychological comorbidity in a mixed chronic pain population. Eighty-one patients (72% women) with chronic pain (>6 months) were included. Patient reported outcomes were collected, and blood was analyzed with the Proseek Multiplex Olink Inflammation Panel (Bioscience Uppsala, Uppsala, Sweden), resulting in 77 inflammatory markers included for multivariate data analysis. Three subgroups of chronic pain patients were identified using an unsupervised principal component analysis. No difference between the subgroups was seen in pain intensity, but differences were seen in mental health and inflammatory profiles. Ten inflammatory proteins were significantly associated with anxiety and depression (using the Generalized Anxiety Disorder 7-item scale (GAD-7) and the Patient Health Questionnaire (PHQ-9): STAMBP, SIRT2, AXIN1, CASP-8, ADA, IL-7, CD40, CXCL1, CXCL5, and CD244. No markers were related to pain intensity. Fifteen proteins could differentiate between patients with moderate/high (GAD-7/PHQ-9 > 10) or mild/no (GAD-7/PHQ-9 < 10) psychological comorbidity. This study further contributes to the increasing knowledge of the importance of inflammation in chronic pain conditions and indicates that specific inflammatory proteins may be related to psychological comorbidity.

A bidirectional study of the association between insomnia, high-sensitivity C-reactive protein, and comorbid low back pain and lower limb pain

OBJECTIVES

To examine the possible bidirectional association between insomnia and comorbid chronic low back pain (LBP) and lower limb pain and to explore whether high-sensitivity C-reactive protein (hsCRP) amplifies these associations.

METHODS

We calculated adjusted risk ratios (RR) with 95% confidence intervals (CI) for the development of insomnia and mild-to-severe chronic LBP and lower limb pain at 11 years follow-up in participants aged ≥32 years and with hsCRP ≤10 mg/L at baseline in 2007-2008: 3,714 without chronic LBP or lower limb pain (sample 1) and 7,892 without insomnia (sample 2).

RESULTS

Compared to participants without chronic pain, participants with comorbid chronic LBP and lower limb pain had a RR of insomnia of 1.37 (95% CI 1.12-1.66). Compared with participants without insomnia, participants with insomnia did not have an increased risk of comorbid chronic LBP and lower limb pain (RR: 1.06, 95% CI 0.76-1.46); however, participants with insomnia had a RR of chronic LBP of 1.20 (95% CI 1.02-1.42). There was no strong amplifying effect of elevated hsCRP (3.00-10.0 mg/L) on these associations.

CONCLUSIONS

These findings suggest that elevated hsCRP does not amplify the associations between insomnia and mild-to-severe chronic LBP and lower limb pain. Further research using data on the temporal relation between insomnia, chronic pain, and inflammatory responses are required to fully understand the causal pathways.

Prefrontally modulated vagal neuroimmunomodulation is associated with telomere length

Background

Accumulated senescent cells are proposed to be one of the main drivers of age-related pathology such as dementia and cancer through disruption of tissue structure and function. We recently proposed the Neuro-Immuno-Senescence Integrative Model (NISIM), which relates prefrontally modulated vagal tone and subsequent balance between vagal and sympathetic input to the spleen to inflammatory responses leading to generation of reactive oxygen species and oxidative telomere damage.

Aim

In this study, we assess inflammation as a mediator in the relationship between prefrontally modulated vagal tone and leukocyte telomere length (LTL). We also assess the relationship between a recently proposed index of vagal neuroimmunomodulation (vagal tone/inflammation ratio; NIM index) and telomere length.

Methods

This study uses participant data from a large nationally representative longitudinal study since 1974 with a total of 45,000 Norwegian residents so far. A sub-sample of 131 participants from which ultrashort recordings (30 s) of vagal tone, c reactive protein, and LTL could be obtained were included in the study. Relationships were analyzed with Pearson's correlations and hierarchical multiple linear regression using either vagal tone and CRP or the NIM index to predict telomere length.

Results

Vagal tone was a significant positive predictor of telomere length but this was not mediated by c reactive protein, even after controlling for confounders. The NIM index was a significant positive predictor of telomere length, also when controlling for confounders. In a follow-up analysis simultaneously comparing telomere length between groups with high and low values of vagal tone, and between groups with high and low NIM index values, telomere length was only significantly different between NIM index groups.

Conclusion

This is the first study suggesting that prefrontally modulated vagal neuroimmunomodulation is associated with telomere length thus supporting the NISIM. Results indicate that the NIM index is a more sensitive indicator of vagal neuroimmunomodulation than vagal tone and CRP in isolation.

No associations between C-reactive protein and spinal pain trajectories in children and adolescents (CHAMPS study-DK)

Preliminary evidence points to a link between C-reactive protein (CRP) and spinal pain in adults. However, there is a paucity of research in younger populations. Therefore, we aimed to determine associations between CRP and spinal pain in childhood and adolescence. We identified trajectories of spinal pain from childhood to adolescence and investigated the associations between CRP and trajectory subgroups. Six- to 11-year-old children from 13 primary schools, were followed from October 2008 and until 2014. High-sensitivity CRP collected at baseline (2008) was measured using serum samples. The outcome was the number of weeks with non-traumatic spinal pain between November 2008 and June 2014. We constructed a trajectory model to identify different spinal pain trajectory subgroups. The associations between CRP and spinal pain trajectory subgroups were modelled using mixed-effects multinominal logistic regression. Data from 1556 participants (52% female), with a mean age of 8.4 years at baseline, identified five spinal pain trajectory subgroups: "no pain" (55.3%), "rare" (23.7%), "rare, increasing" (13.6%), "moderate, increasing" (6.1%), and "early onset, decreasing" (1.3%). There were no differences in baseline high-sensitivity CRP levels between spinal pain trajectory subgroups. Thus, the heterogeneous courses of spinal pain experienced were not defined by differences in CRP at baseline.

Relationship between fatty acid intake and chronic neck/shoulder/upper limb pain without elevated CRP in a Japanese population: a cross-sectional analysis of the Shika study

Although chronic pain (CP) is classified as inflammatory or non-inflammatory, the involvement of fatty acid intake in this process has not yet been examined in detail. Therefore, the present study investigated whether the relationship between CP and fatty acid intake differs between high and low C-reactive protein (CRP) levels in middle-aged and elderly individuals in the Shika study. One-thousand and seven males and 1216 females with mean ages of 68⋅78 and 69⋅65 years, respectively, participated in the present study. CRP was quantified by blood sampling from participants who responded to a CP questionnaire. The brief-type self-administered diet history questionnaire (BDHQ) was used to assess fatty acid intake. Interactions were observed between CP and CRP on monounsaturated fatty acids (MUFA) and eicosadienoic acid in a two-way analysis of covariance adjusted for sex, age, lack of exercise, lack of sleep, current smoking and drinking status, and BMI. MUFA (OR 1⋅359) and eicosadienoic acid (OR 1⋅072) were identified as significant independent variables for CP in a multiple logistic regression analysis, but only in the low CRP group. Only a high intake of MUFA and eicosadienoic acid was associated with chronic neck/shoulder/upper limb pain without elevated CRP. In psychogenic and neuropathic pain without elevated CRP, an increased intake of MUFA and eicosadienoic acid, a family member of n -6 fatty acids, appears to affect CP. Further longitudinal studies are needed to elucidate this relationship.

Pain Sensitivity and Psychiatric Comorbidities in Chronic Pancreatitis Patients With and Without Pain: Past Experience Matters

Background and Aims

Pain is the primary symptom of chronic pancreatitis (CP) and has been associated with abnormal pain processing and psychologic distress. Little is known about these phenomena in patients with painless disease. The aim of this study was to characterize patterns of pain processing and psychologic distress in patients with primary painless vs painful CP.

Methods

This was a cross-sectional multicenter study of 235 patients with definitive CP. Patients were categorized based on current and past pain history; current pain (79%), no current (but prior) pain (11%), and painless CP (10%). Demographic information and clinical data including symptoms of anxiety and depression using the Hospital Anxiety and Depression Scale were collected. All patients underwent quantitative sensory testing to assess patterns of pain processing.

Results

A total of 235 patients (57% males, mean age 53.9 ± 14.0 years, 41% alcohol etiology) were included. Compared to patients with painless CP, enhanced pain sensitivity was observed in both patients with current pain (odds ratio [OR] 3.29; 95% confidence interval [CI] [1.11-9.77], P = .032) and no current pain (OR 4.07; 95% CI [1.10-15.03], P = .035). Patients with current pain also had increased depression prevalence compared to patients with painless CP (OR 6.15; 95% CI [1.28-29.41], P = .023), while no difference was seen for patients with no current pain (OR 1.24; 95% CI [0.19-8.26], P = .824).

Conclusion

Total absence of pain in CP is associated with normal pain processing and low prevalence of psychologic distress, whereas patients with prior pain experience appear to have persistent and enhanced pain sensitivity even in the absence of clinical pain and psychologic distress.

Low Pain Tolerance Is Associated With Coronary Angiography, Coronary Artery Disease, and Mortality: The Tromsø Study

Background

The initial presentation to coronary angiography and extent of coronary artery disease (CAD) vary greatly among patients, from ischemia with no obstructive CAD to myocardial infarction with 3‐vessel disease. Pain tolerance has been suggested as a potential mechanism for the variation in presentation of CAD. We aimed to investigate the association between pain tolerance, coronary angiography, CAD, and death.

Methods and Results

We identified 9576 participants in the Tromsø Study (2007–2008) who completed the cold‐pressor pain test, and had no prior history of CAD. The median follow‐up time was 10.4 years. We applied Cox‐regression models with age as time‐scale to calculate hazard ratios (HR). More women than men aborted the cold pressor test (39% versus 23%). Participants with low pain tolerance had 19% increased risk of coronary angiography (HR, 1.19 [95% CI, 1.03–1.38]) and 22% increased risk of obstructive CAD (HR, 1.22 [95% CI, 1.01–1.47]) adjusted by age as time‐scale and sex. Among women who underwent coronary angiography, low pain tolerance was associated with 54% increased risk of obstructive CAD (HR, 1.54 [95% CI, 1.09–2.18]) compared with high pain tolerance. There was no association between pain tolerance and nonobstructive CAD or clinical presentation to coronary angiography (ie, stable angina, unstable angina, and myocardial infarction). Participants with low pain tolerance had increased risk of mortality after adjustment for CAD and cardiovascular risk factors (HR, 1.40 [95% CI, 1.19–1.64]).

Conclusions

Low cold pressor pain tolerance is associated with a higher risk of coronary angiography and death.

Comparison of Postoperative Quality of Life and Pain with and without a Metal Rib Spreader in Patients Undergoing Lobectomy through Axillary Mini-Thoracotomy for Stage I Lung Cancer

Purpose: To evaluate postoperative patient-reported quality of life (QOL) and pain with and without a metal rib spreader (MRS) in patients with stage I lung cancer who underwent lobectomy through axillary mini-thoracotomy (AMT).

Methods: This single-institution prospective observational study enrolled patients between January 2015 and April 2018. Their QOL and pain were evaluated using the EQ-5D and the European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire 30 items (QLQ-C30). The EQ-5D was completed preoperatively (Pre) and on days 1/3/5/7 (D1/3/5/7), at 1 month (M1), and at 1 year postoperatively (Y1). The EORTC QLQ-C30 was completed at Pre, M1, and Y1.

Results: The data of 140 patients were analyzed (video-assisted without MRS: VA/noMRS: 67, AMT with MRS: AMT/MRS: 73). Although the AMT/MRS group had more preoperative comorbidities, longer operative times, and more blood loss than the VA/noMRS group, the EQ-5D visual analog scale scores were not significantly different at any assessment point (Pre/D1/D3/D5/D7/M1/Y1) (VA/noMRS: 82/48/60/67/73/77/85, AMT/MRS: 80/46/60/66/73/76/85). Postoperative pain in the EQ-5D descriptive system and the EORTC QLQ-C30 was comparable between the groups.

Conclusion: VA/noMRS and AMT/MRS showed similar postoperative QOL and pain scores, indicating that MRS negligibly impacts the postoperative QOL and pain.

Positive affect and distraction enhance while negative affect impairs pain modulation in recurrent low back pain patients and matched controls

ABSTRACT

Pathophysiological causes of low back pain (LBP) remain generally unclear, so focus has shifted to psychosocial features and central pain processing. Effects of attentional and affective manipulation on conditioned pain modulation (CPM) and tonic pain perception were examined in thirty recurrent LBP patients in two sessions, one with and one without clinical pain, and compared to healthy participants. Phasic cuff pressure on one leg, scored on a numerical rating scale (NRS), was used for test-stimuli (TS) and contralateral tonic cuff pain rated on an electronic visual analogue scale (eVAS) was the conditioning-stimulus (CS). TS were assessed before and during: 1) control with no manipulation/CS, 2) three attentional manipulations (Flanker with/without CS or CS-Only), and 3) three affective manipulations (positive, neutral, negative pictures) with CS. Greater inhibition of TS-NRS scores was observed in CS-only (P=0.028), combined CS&attention (P=0.026), and CS&Positive (P=0.006) than Control paradigms, and greater in CS&Positive (P=0.019) than CS&Negative paradigms. eVAS scores of CS pain increased throughout all paradigms with CS (P<0.05), except the CS&Positive paradigm, and greater facilitation was observed in the CS-Only paradigm than all others (P<0.02) and lower facilitation was additionally observed in the CS&Positive paradigm compared to CS&Attention and CS&Negative paradigms (P<0.01). Flanker effects and interruptive effects of CS pain on attention were observed consistent with prior findings, and affective manipulation produced less shift in valence among people with RLBP than controls (P<0.05). Attention and positive affect with CS pain evoked CPM, and all attentional/affective tasks, especially positive affect, reduced facilitation of CS pain.

Dismantling Anti-Ageing Medicine: Why Age-Relatedness of Cardiovascular Disease is Proof of Robustness Rather Than of Ageing-Associated Vulnerability

Ageing is perceived to be the common culprit behind the most prevalent noncommunicable chronic diseases (NCD) such as cardiovascular disease (CVD). Treating ageing as a means to prevent its downstream pathologies has become the logical extension of this idea, and the defining criterion of anti-ageing medicine (evidence-based early detection, prevention, and treatment of age-related diseases). Challenging the underlying rationale, we here argue that the disease's late-in-life occurrence is proof of a genetically conserved robustness that helps us resist disease long enough for it to masquerade as a consequence of living long rather than of living wrong. Robustness is an acknowledged hallmark phenomenon of all complex systems (while there exists no universally adopted definition, a hallmark of complex systems is that they consist of many networked components whose interactions may give rise to system behaviors which cannot be derived or predicted from a reductionist knowledge of the interacting parts, even if this knowledge is complete) and a key concept in the complexity sciences (a relatively new branch of science that attempts to find and understand the common mechanisms and patterns shared by all complex systems). To reconceptualise the age-relatedness of chronic diseases in this sense has important implications for medical research and practice. The goal of our essay is to open a discussion that may enhance the overall understanding of robustness and prevent a misguided redirection of funding away from established disease specific research and towards anti-ageing medicine. This essay is timely, as the forthcoming 11^th version of the International Classification of Diseases (ICD) will be the first to recognise ageing as a condition, thereby legitimising anti-ageing medical research. On a more pragmatic note, and for the benefit of people alive today, we propose a practical strategy to remedy the mismatch between heritable robustness and the lifestyle challenges that gradually overwhelm it.

Ketogenic diets and the nervous system: a scoping review of neurological outcomes from nutritional ketosis in animal studies

OBJECTIVES

Ketogenic diets have reported efficacy for neurological dysfunctions; however, there are limited published human clinical trials elucidating the mechanisms by which nutritional ketosis produces therapeutic effects. The purpose of this present study was to investigate animal models that report variations in nervous system function by changing from a standard animal diet to a ketogenic diet, synthesise these into broad themes, and compare these with mechanisms reported as targets in pain neuroscience to inform human chronic pain trials.

METHODS

An electronic search of seven databases was conducted in July 2020. Two independent reviewers screened studies for eligibility, and descriptive outcomes relating to nervous system function were extracted for a thematic analysis, then synthesised into broad themes.

RESULTS

In total, 170 studies from eighteen different disease models were identified and grouped into fourteen broad themes: alterations in cellular energetics and metabolism, biochemical, cortical excitability, epigenetic regulation, mitochondrial function, neuroinflammation, neuroplasticity, neuroprotection, neurotransmitter function, nociception, redox balance, signalling pathways, synaptic transmission and vascular supply.

DISCUSSION

The mechanisms presented centred around the reduction of inflammation and oxidative stress as well as a reduction in nervous system excitability. Given the multiple potential mechanisms presented, it is likely that many of these are involved synergistically and undergo adaptive processes within the human body, and controlled animal models that limit the investigation to a particular pathway in isolation may reach differing conclusions. Attention is required when translating this information to human chronic pain populations owing to the limitations outlined from the animal research.

Decreased pain sensitivity and alterations of cerebrospinal fluid and plasma inflammatory mediators after total hip arthroplasty in patients with disabling osteoarthritis

BACKGROUND

Proinflammatory mechanisms are implicated in pain states. Recent research indicates that patients with osteoarthritis (OA) with signs of central sensitization exhibit elevated cerebrospinal fluid (CSF) levels of interferon gamma-induced protein 10 (IP-10), Fms-related tyrosine kinase 1 (Flt-1), and monocyte chemoattractant protein 1 (MCP-1).

METHODS

The current prospective cohort study, including 15 patients with OA, primarily aimed to evaluate associations among alterations in CSF IP-10, Flt-1, MCP-1, and pain sensitization following total hip arthroplasty (THA). Participants provided CSF and blood samples for analysis of 10 proinflammatory mediators, and underwent detailed clinical examination and quantitative sensory testing, immediately preoperative and 18 months after surgery.

RESULTS

Neurophysiological measures of pain showed markedly reduced pain sensitivity long-term postoperative. Increases in remote site pressure pain detection thresholds (PPDTs) and decreased temporal summation indicated partial resolution of previous central sensitization. Compared to preoperative, CSF concentrations of IP-10 were increased (p = 0.041), whereas neither Flt-1 (p = 0.112) nor MCP-1 levels changed (p = 0.650). Compared to preoperative, plasma concentrations of IP-10 were increased (p = 0.006), whereas interleukin (IL)-8 was decreased (p = 0.023). Subjects who exhibited increases in arm PPDTs above median showed greater increases in CSF IP-10 compared to those with PPDT increases below median (p = 0.028). Analyses of plasma IP-10 and IL-8 indicated higher levels of peripheral inflammation were linked to decreased pressure pain thresholds (unadjusted β = -0.79, p = 0.006, and β = -118.1, p = 0.014, respectively).

CONCLUSIONS

THA leads to long-term decreases in pain sensitivity, indicative of resolution of sensitization processes. Changes in CSF and plasma levels of IP-10, and plasma IL-8, may be associated with altered pain phenotype.

Sex Differences, Sleep Disturbance and Risk of Persistent Pain Associated With Groin Hernia Surgery: A Nationwide Register-Based Cohort Study

Persistent pain after groin hernia repair is a major health problem. Sleep disturbance is associated with heightened pain sensitivity. The main objective of this study was to examine the role of sleep disturbance in the development and long-term maintenance of chronic postherniorrhaphy inguinal pain (CPIP), with exploration of sex differences. From 2012 to 2017, a national cohort of patients with prior groin hernia repair (n = 2084;45.8% females) were assessed for the development of CPIP 12 months after surgery. Patients then underwent long-term (median 5.0 years) follow-up to evaluate the contribution of sex and sleep disturbance on the maintenance of CPIP. Associations between pre- and postoperative sleep problems (assessed at long-term follow-up) and CPIP were tested using logistic regression. Females had higher rates of CPIP with negative impact on daily activities 12 months after surgery as compared to males (14.6 vs 9.2%, P < .0005), and were more likely to have moderate-severe CPIP in the long-term (3.1 vs 1.2%, P = .003). Preoperative sleep problems predicted development of CPIP 12 months after surgery (adjusted odds ratio [aOR] 1.76 [95%CI 1.26-2.46], P = .001) and CPIP in the long-term (aOR 2.20 [1.61-3.00] , P < .0001). CPIP was associated with insomnia and depression. Sleep disturbance may increase the risk for CPIP, and contribute to maintenance of postsurgical pain. PERSPECTIVE: Females are at heightened risk for CPIP as compared to males. Increased severity of pain symptoms are linked to poorer sleep and psychiatric morbidity. Given the robust associations between sleep disturbance and CPIP, interventions which consolidate and promote sleep, especially in females, may improve long-term pain control.

What Does CATS Have to Do With Cancer? The Cognitive Activation Theory of Stress (CATS) Forms the SURGE Model of Chronic Post-surgical Pain in Women With Breast Cancer

Chronic post-surgical pain (CPSP) represents a highly prevalent and significant clinical problem. Both major and minor surgeries entail risks of developing CPSP, and cancer-related surgery is no exception. As an example, more than 40% of women undergoing breast cancer surgery struggle with CPSP years after surgery. While we do not fully understand the pathophysiology of CPSP, we know it is multifaceted with biological, social, and psychological factors contributing. The aim of this review is to advocate for the role of response outcome expectancies in the development of CPSP following breast cancer surgery. We propose the Cognitive Activation Theory of Stress (CATS) as an applicable theoretical framework detailing the potential role of cortisol regulation, inflammation, and inflammatory-induced sickness behavior in CPSP. Drawing on learning theory and activation theory, CATS offers psychobiological explanations for the relationship between stress and health, where acquired expectancies are crucial in determining the stress response and health outcomes. Based on existing knowledge about risk factors for CPSP, and in line with the CATS position, we propose the SURGEry outcome expectancy (SURGE) model of CPSP. According to SURGE, expectancies impact stress physiology, inflammation, and fear-based learning influencing the development and persistence of CPSP. SURGE further proposes that generalized response outcome expectancies drive adaptive or maladaptive stress responses in the time around surgery, where coping dampens the stress response, while helplessness and hopelessness sustains it. A sustained stress response may contribute to central sensitization, alterations in functional brain networks and excessive fear-based learning. This sets the stage for a prolonged state of inflammatory-induced sickness behavior - potentially driving and maintaining CPSP. Finally, as psychological factors are modifiable, robust and potent predictors of CPSP, we suggest hypnosis as an effective intervention strategy targeting response outcome expectancies. We here argue that presurgical clinical hypnosis has the potential of preventing CPSP in women with breast cancer.

A population-based study of inflammatory mechanisms and pain sensitivity

Two recent studies suggest that experimental pain sensitivity is associated with low-grade systemic inflammation. However, only 2 biomarkers have been identified, and the studies were conducted in adult individuals where confounding effects of comorbid diseases cannot be excluded. We therefore tested associations between pain sensitivity and 119 inflammation-related serum biomarkers in 827 healthy adolescents (15-19 years) in the population-based Tromsø Study: Fit Futures. The main outcome measure was cold-pressor pain tolerance (CPT), tested by placing the dominant hand in circulating cold (3°C) water for a maximum of 105 seconds. Secondary outcomes were heat and pressure pain threshold and tolerance. Twelve proteins and 6 fatty acids were significantly associated with CPT after adjustment for possible confounding factors and correction for multiple comparisons. Of these, all fatty acids and 10 proteins were protective, ie, higher biomarkers levels were associated with increased CPT, whereas 2 biomarkers were associated with lower tolerance. Taken together, these biomarkers predicted completion of the tolerance test with a C-statistic of 0.65. Results for heat and pressure pain tolerance were remarkably similar, strengthening the generalizability of our findings. In this cohort of young healthy individuals, we found a relationship between inflammation-related biomarkers and pain tolerance and thresholds. Biomarkers with anti-inflammatory and analgesic effects predominated, suggesting that the development of prophylactic dietary or pharmaceutical treatments may be possible.

Multi-trajectory analysis of C-reactive protein and low back pain from adolescence to early adulthood

PURPOSE

To identify low back pain (LBP) trajectories from early adolescence through to early adulthood and to investigate whether sustained levels of elevated subclinical C-reactive protein (CRP) are linked with these LBP trajectories.

METHODS

We analysed longitudinal data from 1513 participants who were enrolled in the Raine Study cohort. Data on LBP with impact on daily living and CRP were collected at the ages of 14, 17, 20, and 22. We constructed group-based trajectory models to identify discrete trajectories of LBP with impact. We then evaluated how the CRP trajectories and the LBP with impact trajectories evolved jointly over time using a multi-trajectory analysis.

RESULTS

The model identified three LBP trajectories. One subgroup included almost half the participants (46.1%) who had a consistently low probability of LBP. Another subgroup comprising 43.5% of participants had an increasing probability of LBP, while one in ten participants (10.4%) had a decreasing probability of LBP. There were no associations between elevated CRP and LBP trajectory subgroup membership.

CONCLUSION

Although young people follow distinct trajectories of LBP, CRP trajectories do not appear to be a distinguishing factor of the LBP trajectories. Previously reported associations between CRP and LBP may be explained by comorbidity or other factors. Future studies undertaking trajectory analysis should consider comorbidity clusters.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

Characteristics of headache attributed to COVID-19 infection and predictors of its frequency and intensity: A cross sectional study

OBJECTIVE

To study the characteristics of headache attributed to COVID-19 infection and predictors of its severity.

METHODS

A cross-sectional study involved 172 individuals who had headache due to COVID-19 infection. A detailed analysis of such headache was done through a face-to-face interview. Patients with any other form of secondary headache were excluded. Labs, including lymphocytic count, C-reactive protein, D-dimer and ferritin and chest imaging, were made available.

RESULTS: THE

majority of our patients had a diffuse headache (52.9%). It was pressing in 40.7%, with median intensity of 7 (assessed by visual analogue scale) and median frequency of 7 days/week. Patients with preexisting primary headache (52.9%) had significantly more frequent COVID-19 related headache than those without (47.1%) (p = 0.001). Dehydrated patients (64.5%) had more frequent COVID-19 related headache than those who were not dehydrated (35.5%) (p = 0.029). Patients with fever (69.8%) had significantly higher frequency and intensity of COVID-19 related headache compared to those without fever (30.2%) (p = 0.003, 0.012). Patients with comorbidities (19.8%) had significantly higher frequency and intensity of headache than those without comorbidities (80.2%) (p = 0.006, 0.003). After multiple linear regression, primary headache disorders, dehydration and comorbidities were considered predictors of frequency of COVID-19 related headache. Meanwhile, fever and dehydration were predictors of pain intensity.

CONCLUSION

Healthcare providers of COVID-19 patients need to be aware of frequency and intensity predictors of COVID-19 related headache: Primary headache disorders, fever, dehydration, and comorbidities.

High sensitivity C-reactive protein and risk of migraine in a 11-year follow-up with data from the Nord-Trøndelag health surveys 2006-2008 and 2017-2019

Background

Several previous studies have reported a cross-sectional association between elevated high sensitivity C-reactive protein (hs-CRP) and migraine. The aim of this population-based follow-up study was to investigate the influence of hs-CRP at baseline on the risk of developing migraine 11 years later.

Methods

Data from the Nord-Trøndelag Health Study performed in 2006–2008 (baseline) and 2017–2019 were used. A total of 19,574 participants without migraine at baseline were divided into three groups based on hs-CRP levels (< 3 mg/L, 3–9.99 mg/L and 10.00–20 mg/L). Poisson regression was used to evaluate the associations between hs-CRP levels and risk ratios (RRs) of migraine, and precision of the estimates was assessed by 95% confidence interval (CIs).

Results

In the multi-adjusted model, increased risk of migraine (RR 1.46, 95% CI 1.05–2.04) was found in the highest hs-CRP levels group compared to the lowest group. In the group with the highest hs-CRP levels, a nearly three times higher risk of chronic migraine (RR 2.81, 95% CI 1.12–7.06) was found, whereas no evident relationship was found between high hs-CRP level and risk of developing episodic migraine.

Conclusions

The main finding in this 11-year follow-up was that hs-CRP levels between 10.00–20.00 mg/L at baseline was associated with increased risk of chronic migraine.

Genetics and Gender in Acute Pain and Perioperative Opioid Analgesia

Experimental and clinical acute pain research in relation to biological sex and genetics started in the 1980s. Research methods became more powerful and sensitive with the advancement in affordable gene sequencing methods and high-throughput genetic assays. Decades of research has identified several potential pharmaceutical targets, providing insights into future research direction, and understanding of acute pain and opioid analgesic effects in the clinical setting. However, there is insufficient evidence to make generalized recommendations for using genetic tests for clinical practice of acute pain management.

A clinically feasible method for the assessment and characterization of pain in patients with chronic pancreatitis

BACKGROUND AND AIMS

Pain is the primary symptom of chronic pancreatitis (CP), but methods for sensory testing and pain characterization have not previously been validated for clinical use. We present a clinically feasible method for the assessment and characterization of pain mechanisms in patients with CP based on quantitative sensory testing (QST).

METHODS

This was a cross-sectional, multicenter study of 122 control subjects without pancreatic disease and another 60 patients with painful CP. All subjects underwent standardized QST assessments including a cold pressor test, a conditioned pain modulation paradigm, repetitive pin-prick stimuli (temporal summation) and pressure stimulation of the upper abdominal (pancreatic) and control dermatomes. The effects of age and gender on QST assessment parameters were investigated and normative reference values based on quartile regression were derived and implemented in algorithms to categorize patients according to their patterns of central pain processing (normal vs. segmental sensitization vs. widespread sensitization).

RESULTS

Absolute pressure thresholds were subject to clinically relevant gender effects (all p < 0.001), while the remainder of QST parameters were unaffected by age and gender. The algorithm with the best discriminatory capacity showed good separation between patients and controls (p < 0.001); 50% of patients had normal central pain processing, 23% had evidence of segmental sensitization and 27% had evidence of widespread sensitization.

CONCLUSION

We show normative reference values for a clinically feasible method for assessment and characterization of pain mechanisms in patients with CP. Application of this method streamlines the evaluation of pancreatic pain and may be used to inform treatment. CLINICALTRIALS.

GOV ID

NCT03434392.

The impact of C-reactive protein levels on headache frequency in the HUNT study 2006-2008

BACKGROUND

Increased high sensitivity C- reactive protein (hs-CRP) levels have been found in many earlier studies on migraine, and recently also in persons with migraine and insomnia. The aim of this study was to see whether these findings could be reproduced in a large-scale population-based study.

METHODS

A total of 50,807 (54%) out of 94,194 invited aged ≥20 years or older participated in the third wave of the Nord-Trøndelag Health Study study performed in 2006-2008. Among these, 38,807 (41%) had valid measures of hs-CRP and answered questions on headache and insomnia. Elevated hs-CRP was defined as > 3.0 mg/L. The cross-sectional association with headache was estimated by multivariate analyses using multiple logistic regression. The precision of the odds ratio (OR) was assessed with 95% confidence interval (CI).

RESULTS

In the fully adjusted model, elevated hs-CRP was associated with migraine (OR 1.14, 95% CI 1.04-1.25) and migraine with aura (OR 1.15, 95% CI 1.03-1.29). The association was strongest among individuals with headache ≥15 days/month for any headache (OR 1.26, 95% CI 1.08-1.48), migraine (OR 1.62, 95% CI 1.21-2.17), and migraine with aura (OR 1.84, 95% CI 1.27-2.67). No clear relationship was found between elevated hs-CRP and headache less than 7 days/month or with insomnia.

CONCLUSIONS

Cross-sectional data from this large-scale population-based study showed that elevated hs-CRP was associated with headache ≥7 days/month, especially evident for migraine with aura.

Contribution of microglial reaction to increased nociceptive responses in high-fat-diet (HFD)-induced obesity in male mice

The progressive increase in the prevalence of obesity in the population can result in increased healthcare costs and demands. Recent studies have revealed a positive correlation between pain and obesity, although the underlying mechanisms still remain unknown. Here, we aimed to clarify the role of microglia in altered pain behaviors induced by high-fat diet (HFD) in male mice. We found that C57BL/6CR mice on HFD exhibited enhanced spinal microglial reaction (increased cell number and up-regulated expression of p-p38 and CD16/32), increased tumor necrosis factor-α (TNF-α) mRNA and brain-derived neurotrophic factor (BDNF) protein expression as well as a polarization of spinal microglial toward a pro-inflammatory phenotype. Moreover, we found that using PLX3397 (a selective colony-stimulating factor-1 receptor (CSF1R) kinase inhibitor) to eliminate microglia in HFD-induced obesity mice, inflammation in the spinal cord was rescued, as was abnormal pain hypersensitivity. Intrathecal injection of Mac-1-saporin (a saporin-conjugated anti-mac1 antibody) resulted in a decreased number of microglia and attenuated both mechanical allodynia and thermal hyperalgesia in HFD-fed mice. These results indicate that the pro-inflammatory functions of spinal microglia have a special relevance to abnormal pain hypersensitivity in HFD-induced obesity mice. In conclusion, our data suggest that HFD induces a classical reaction of microglia, characterized by an enhanced phosphorylation of p-38 and increased CD16/32 expression, which may in part contribute to increased nociceptive responses in HFD-induced obesity mice.

The association between insomnia, c-reactive protein, and chronic low back pain: cross-sectional analysis of the HUNT study, Norway

BACKGROUND AND AIMS

Chronic low back pain (chronic LBP) is the number one cause for years lived with disability among 301 diseases and injuries analyzed by The Global Burden of Disease study 2013. Insomnia is highly prevalent among people with chronic LBP. To explain the sleep-pain relationship, theoretical models propose that insomnia symptoms may be associated with increased basal inflammation, operationalized as c-reactive protein (CRP) and lead to further pain and disrupted sleep. We aimed to determine the associations between insomnia, chronic LBP, and inflammation (operationalized as CRP), whilst controlling for age, body mass index, smoking, physical activity, depression, anxiety and osteoarthritis.

METHODS

A cross-sectional analysis of the third Nord-Trøndelag Health Study (2006-2008), a rural population survey of 50,666 participants in Norway aged 20-96 years. Insomnia (dichotomous) was defined according to the Diagnostic and Statistical Manual of Mental Disorders 5th Edition, and chronic LBP (dichotomous) as low back pain or stiffness lasting at least 3 months. Data for CRP were obtained from non-fasting serum samples and assessed via latex immunoassay methodology. We excluded participants with the following self-reported chronic somatic diseases: chronic heart failure, chronic obstructive pulmonary disease, rheumatoid arthritis, fibromyalgia or ankylosing spondylosis. Possible associations between presence of insomnia and presence of chronic LBP (dependent), and the level of CRP and presence of chronic LBP (dependent), were assessed using logistic regression models. The possible association between insomnia and CRP (dependent) was assessed using linear regression. Multivariable analyses were conducted adjusting for confounders stated in our aim that achieved p ≤ 0.2 in univariate regressions. We performed stratified analyses for participants with "Normal" (<3 mg/L) "Elevated" (3-10 mg/L) and "Very High" (>10 mg/L) levels of CRP.

RESULTS

In our total included sample (n = 30,669, median age 52.6, 54% female), 6.1% had insomnia (n = 1,871), 21.4% had chronic LBP (n = 6,559), and 2.4% had both (n = 719). Twenty four thousand two hundred eighty-eight (79%) participants had "Normal" CRP, 5,275 (17%) had "Elevated" CRP, and 1,136 (4%) had "Very High" CRP. For participants with "Normal" levels of CRP, insomnia was associated with higher levels of CRP (adjusted B = 0.04, 95%CI [0.00-0.08], p = 0.046), but not for people with "Elevated" or "Very High" levels of CRP. There was an association between CRP and presence of chronic LBP in the total sample (adjusted OR = 1.01, [1.00-1.01], p = 0.013) and for people with "Normal" CRP (1.05, [1.00-1.10, p = 0.034]. Insomnia was associated with the presence of chronic LBP in the total sample (adjusted OR = 1.99, 95%CI [1.79-2.21], <0.001) and for people with "Normal", "Elevated" and "Very High".

CONCLUSIONS

Individuals with insomnia have twice the odds of reporting chronic LBP. Insomnia, CRP and chronic LBP appear to be linked but the role of CRP appears to be limited. Longitudinal studies may help further explore the causal inference between insomnia chronic LBP, and inflammation.

IMPLICATIONS

Given the strong relationship between insomnia and chronic LBP, screening and management of comorbid insomnia and chronic LBP should be considered in clinical practice. Further longitudinal studies are required to explore whether the presence of insomnia and increased inflammation affects the development of chronic LBP.

What makes surgical nerve injury painful? A 4-year to 9-year follow-up of patients with intercostobrachial nerve resection in women treated for breast cancer

Nerve injury during breast cancer surgery can cause neuropathic pain (NP). It is not known why some, but not all, patients develop chronic postsurgical neuropathic pain (CPSNP) after the same nerve injury. In this study, we examined 251 breast cancer survivors with surgeon-verified intercostobrachial nerve resection to identify factors that associate with CPSNP. The patients were recruited from a previous study of 1000 women treated for breast cancer in 2006 to 2010. This enabled us to analyze preoperative factors that associate with future CPSNP. The patients were re-examined in 2014 to 2016 to diagnose CPSNP using the revised NP diagnostic criteria. Preoperative assessments were pain in the area to be operated on, any chronic pain condition, depressive symptoms, anxiety, sleep, and experimental cold pain sensitivity using the cold pressor test (CPT). Follow-up assessments were CPT, psychological factors, sleep, any chronic pain, and basic laboratory tests. One hundred thirty-seven (55%) patients with intercostobrachial nerve resection fulfilled CPSNP diagnostic criteria after 4 to 9 years. Of them, 30 patients (22%) had moderate to severe pain in self-reports and 86 (63%) presented moderate to severe evoked pain at examination. Preoperative pain in the surgical area, other chronic pains, and breast-conserving surgery were associated with future CPSNP. Other chronic pains, increased psychological burden, and insomnia, both before surgery and at the follow-up, were associated with CPSNP. Preoperative CPT did not associate with future CPSNP. Patients with established CPSNP showed increased pain sensitivity in CPT and higher levels of inflammatory markers, suggesting that central sensitization and inflammation may associate with the maintenance of CPSNP.

Genetic variation in P2RX7 and pain tolerance

P2X7 is a nonselective cation channel activated by extracellular ATP. P2X7 activation contributes to the proinflammatory response to injury or bacterial invasion and mediates apoptosis. Recently, P2X7 function has been linked to chronic inflammatory and neuropathic pain. P2X7 may contribute to pain modulation both by effects on peripheral tissue injury underlying clinical pain states, and through alterations in central nervous system processing, as suggested by animal models. To further test its role in pain sensitivity, we examined whether variation within the P2RX7 gene, which encodes the P2X7 receptor, was associated with experimentally induced pain in human patients. Experimental pain was assessed in Tromsø 6, a longitudinal and cross-sectional population-based study (N = 3016), and the BrePainGen cohort, consisting of patients who underwent breast cancer surgery (N = 831). For both cohorts, experimental pain intensity and tolerance were assessed with the cold-pressor test. In addition, multisite chronic pain was assessed in Tromsø 6 and pain intensity 1 week after surgery was assessed in BrePainGen. We tested whether the single-nucleotide polymorphism rs7958311, previously implicated in clinical pain, was associated with experimental and clinical pain phenotypes. In addition, we examined effects of single-nucleotide polymorphisms rs208294 and rs208296, for which previous results have been equivocal. Rs7958311 was associated with experimental pain intensity in the meta-analysis of both cohorts. Significant associations were also found for multisite pain and postoperative pain. Our results strengthen the existing evidence and suggest that P2X7 and genetic variation in the P2RX7-gene may be involved in the modulation of human pain sensitivity.

Neuroimmune modulation of pain across the developmental spectrum

Today's treatment for chronic pain is inadequate, and novel targets need to be identified. This requires a better understanding of the mechanisms involved in pain sensitization and chronification. In this review, we discuss how peripheral inflammation, as occurs during an infection, modulates the central pain system. In rodents, neonatal inflammation leads to increased pain sensitivity in adulthood by priming immune components both peripherally and centrally. The excitability of neurons in the spinal cord is also altered by neonatal inflammation and may add to pain sensitization later in life. In adult humans, inflammation modulates pain sensitivity as well, partly by affecting the activity in brain areas that process and regulate pain signals. Low-grade inflammation is common in clinical populations both peripherally and centrally, and priming of the immune system has also been suggested in some pain populations. The nociceptive and immune systems are primed by infections and inflammation. The early life programming of nociceptive responses following exposure to infections or inflammation will define individual differences in adult pain perception. Immune-to-brain mechanisms and neuroimmune pathway need further investigation as they may serve both as predictors and therapeutic targets in chronic pain.

Does insomnia modify the association between C-reactive protein and migraine? The Tromsø Study 2015-2016

BACKGROUND

The relationship between high sensitivity C-reactive protein and migraine is unclear. The aim of this cross-sectional population-based study was to investigate the association between high sensitivity C-reactive protein and types of headache, and to evaluate the impact of insomnia on this association.

METHODS

A total of 20,486 (63%) out of 32,591 invited, aged ≥40 years or older, participated in the seventh wave of the Tromsø study conducted in 2015-2016 and had valid information on headache, insomnia and high sensitivity C-reactive protein. The influence of insomnia on the association between questionnaire-based diagnoses of headache and elevated high sensitivity C-reactive protein defined as >3.0 mg/L was assessed using multiple logistic regression, estimating prevalence odds ratio with 95% confidence intervals.

RESULTS

A total of 6290 participants (30.7%) suffered from headache during the last year. Among these, 1736 (8.5%) fulfilled the criteria of migraine, 991 (4.8%) had migraine with aura, 746 (3.6%) migraine without aura (3.8%), and 4554 (22.2%) had non-migrainous headache. In the final multi-adjusted analysis, elevated high sensitivity C-reactive protein was associated with headache (odds ratio 1.10, 95% confidence interval 1.01-1.20), migraine (odds ratio 1.17, 95% confidence interval 1.01-1.35), and migraine with aura (odds ratio 1.23, 95% confidence interval 1.01-1.53). No association was found between elevated high sensitivity C-reactive protein and migraine without aura or non-migrainous headache. The association between high sensitivity C-reactive protein and migraine was strongly dependent on insomnia status. Among individuals with insomnia, elevated high sensitivity C-reactive protein was associated with migraine (odds ratio 1.49, 95% confidence interval 1.02-2.17), and migraine with aura (odds ratio 1.59, 95% confidence interval 1.03-2.45), whereas no such relationship was found among those without insomnia.

CONCLUSIONS

In this cross-sectional study, participants with migraine, in particular migraine with aura, were more likely to have elevated high sensitivity C-reactive protein, evident only among those with insomnia.

Salivary Inflammatory Markers in Trichotillomania: A Pilot Study

BACKGROUND

Immune dysregulation has been hypothesized to be important in the development and pathophysiology of compulsive disorders such as obsessive compulsive disorder (OCD), which has a high comorbid overlap with trichotillomania (both are OC-related disorders). The role of inflammation in the pathophysiology of trichotillomania has garnered little research to date.

METHODS

Individuals with trichotillomania provided saliva sample for analysis of inflammatory cytokines. Additionally, these participants were examined on a variety of demographic variables (including body mass index [BMI], previously found to relate to inflammation) along with clinical measures (symptom severity, functioning, and comorbidity).

RESULTS

Thirty-one participants, mean age of 24.7 (±10.2) years, 27 (87.1%) females were -included. The mean score on the Massachusetts General Hospital Hair Pulling Scale was 15.7 (±4.2), reflective of moderate symptom severity. Compared to normative data, the mean inflammatory marker levels in the trichotillomania sample had the following Z scores: interleukin-1β (IL-1β) Z = -0.26, IL-6 Z = -0.39, IL-8 Z = -0.32, and tumor necrosis factor-α Z = -0.83. Levels of inflammatory markers did not correlate significantly with BMI, depressive mood, symptom severity, or disability.

CONCLUSIONS

The relatively low level of inflammatory saliva cytokines observed in the current study (negative z scores versus normative data with medium effect sizes) indicates that evaluation of blood inflammatory levels in trichotillomania versus matched controls would be valuable in future work. If a hypoinflammatory state is confirmed -using blood samples, this would differentiate trichotillomania from other mental disorders (such as OCD, schizophrenia, and depression), which have typically been linked with high inflammatory measures in the literature, at least in some cases.

Chronic intensive care-related pain: Exploratory analysis on predictors and influence on health-related quality of life

BACKGROUND

There is growing evidence for the development of chronic pain after intensive care. Nonetheless, there is only limited knowledge about factors leading to chronic intensive care-related pain (CIRP). Thus, the primary objective was the identification of predictors of CIRP. Moreover, we aimed to assess the impact of CIRP on patients' health-related quality of Life (HRQOL).

METHODS

Comprehensive information on patients' pain before ICU admission and present pain was collected longitudinally by means of the German Pain Questionnaire 6 and 12 months after ICU discharge (ICU_DC ). In addition, a subsample of patients underwent Quantitative Sensory Testing (QST). We used Generalized Estimating Equations to identify predictors of CIRP with logistic regression models.

RESULTS

In total, 204 patients (197/159 at 6/12 months after ICU_DC ) were available for the analyses. In the multivariate models, moderate to severe average pain in the 4 weeks after ICU_DC , lower age, female sex, increased inflammation and chronic pain conditions and increased levels of anxiety before ICU admission were predictive for CIRP. In addition, small fibre deficits and lower disease severity were associated with CIRP in the QST subsample (81 patients, 77/55 at 6/12 months after ICU_DC ). Patients with CIRP reported significantly lower HRQOL than patients without CIRP.

CONCLUSIONS

Chronic intensive care-related pain is associated with specific decrements in HRQOL. Knowledge about the identified predictors is of clinical and scientific importance and might help to reduce the incidence of CIRP.

SIGNIFICANCE

Chronic intensive care-related pain is associated with specific decrements in health-related quality of life. While most of the identified predictors for CIRP can only be considered as risk factors, especially adequate (post-) acute pain management should be studied as preventive strategy.

The impact of the Standard American Diet in rats: Effects on behavior, physiology and recovery from inflammatory injury

BACKGROUND AND AIMS

Obesity is a significant health concern in the Western world and the presence of comorbid conditions suggests an interaction. The overlapping distributions of chronic pain populations and obesity suggests that an interaction may exist. Poor quality diet (high carbohydrates, saturated fats, omega-6 polyunsaturated fatty acids) can lead to increased adiposity which can activate immune cells independent of the activating effect of the diet components themselves. This dual action can contribute to chronic inflammation that may alter susceptibility to chronic pain and prolong recovery from injury. However, traditional examinations of diet focus on high-fat diets that often contain a single source of fat, that is not reflective of an American diet. Thus, we examined the impact of a novel human-relevant (high-carbohydrate) American diet on measures of pain and inflammation in rats, as well as the effect on recovery and immune cell activation.

METHODS

We developed a novel, human-relevant Standard American Diet (SAD) to better model the kilocalorie levels and nutrient sources in an American population. Male and female rats were fed the SAD over the course of 20 weeks prior to persistent inflammatory pain induction with Complete Freund's Adjuvant (CFA). Mechanical and thermal sensitivity were measured weekly. Spontaneous pain, open field locomotion and blood glucose levels were measured during diet consumption. Body composition was assessed at 20 weeks. Following full recovery from CFA-induced hypersensitivity, blood was analyzed for inflammatory mediators and spinal cords were immunohistochemically processed for microglial markers.

RESULTS

Chronic consumption of the SAD increased fat mass, decreased lean mass and reduce bone mineral density. SAD-fed rats had increased leptin levels and pro-inflammatory cytokines in peripheral blood serum. Following CFA administration, mechanical sensitivity was assessed and recovery was delayed significantly in SAD-fed animals. Sex differences in the impact of the SAD were also observed. The SAD increased body weight and common T-cell related inflammatory mediators in female, but not male, animals. In males, the SAD had a greater effect on bone mineral density and body composition. Long-term consumption of the SAD resulted in elevated microglial staining in the dorsal horn of the spinal cord, but no sex differences were observed.

CONCLUSIONS

We demonstrate the negative effects of an American diet on physiology, behavior and recovery from injury. SAD consumption elevated pro-inflammatory mediators and increased microglial activation in the spinal cord. While there were sex differences in weight gain and inflammation, both sexes showed prolonged recovery from injury.

IMPLICATIONS

These data suggest that poor quality diet may increase susceptibility to chronic pain due to persistent peripheral and central immune system activation. Furthermore, consumption of a diet that is high in carbohydrates and omega-6 polyunsaturated fatty acid is likely to lead to protracted recovery following trauma or surgical procedures. These data suggest that recovery of a number of patients eating a poor quality diet may be expedited with a change in diet to one that is healthier.