Central sensitization predicts greater fatigue independently of musculoskeletal pain

Relationship of cancer-related fatigue with psychoneurophysiological (PNP) symptoms in breast cancer survivors

PURPOSE

Cancer-related fatigue (CRF) is a highly prevalent and debilitating symptom reported by breast cancer survivors (BCS). CRF has been associated with the co-occurrence of anxiety, depression, poor sleep quality, cognitive impairment, which are collectively termed as psychoneurophysiological (PNP) symptoms. CRF and these PNP symptoms are often reported during and after treatment with long-lasting distress. It is unclear how CRF and these PNP symptoms influence each other. This study aimed to explore predictive factors (i.e., PNP symptoms and social-demographic factors) of CRF, and test exploratory path models of the relationships of CRF with PNP symptoms (depression, anxiety, sleep disturbance, pain, and cognitive function) in BCS.

METHODS

This paper is part of a larger descriptive, correlational, and cross-sectional study. Validated and reliable instruments assessed CRF, depression, anxiety, sleep disturbance, pain, and cognitive function. Descriptive statistics, Pearson correlation, multiple linear regression models, and path analysis were employed.

RESULTS

Patients (N = 373) who reported less bodily pain had worst CRF (r = -0.45, p < .01). Significant predictors of CRF included depression, sleep disorder, bodily pain, perceived cognitive ability, and dispositional (state) optimism. Depression alone accounted for 31% of the variance in CRF. An integrative path model with bodily pain, neuropathic pain, CRF, and depression showed a good fit across different indices (CFI = 0.993, RMSEA = 0.047, 90% CI 0-0.12, SRMR = 0.027).

CONCLUSIONS

This study identified significant predictors of CRF and revealed a good fit mediation model with significant pathways for CRF, suggesting that a common etiology may underpin the co-occurrence of CRF with PNP symptoms (pain and depression). However, further investigation with longitudinal design is necessary to explore the causal relationships of these symptoms. Evidence-based strategies/interventions are needed to reduce or eliminate the burden of these symptoms on the lives of BCS.

The Influence of Physical, Mental, and Cognitive Factors on Health-Related Quality of Life among Community-Dwelling Older Adults: A Focus on Central Sensitization-Related Symptoms

Most older adults wish to maintain independence in their familiar communities. However, many experience pain and pain-related disabilities which reduce their health-related quality of life (HRQOL), leading to increased hospitalizations and mortality. This study aimed to determine the impact of physical, mental, and cognitive factors, particularly central sensitization-related symptoms (CSS), on the HRQOL of community-dwelling older adults. A total of 206 participants were included in the analysis, which measured HRQOL, basic attributes, physical functions and body pain, mental factors, cognitive factors, and CSS severity using validated tools. A correlation analysis was used to examine the association between HRQOL and each measure. Furthermore, multiple regression analysis (forced entry method) was performed to identify the factors influencing the HRQOL. The study found that pain intensity and CSS severity significantly influenced the HRQOL among community-dwelling older adults. The higher the pain intensity and CSS severity, the lower their HRQOL. The participants had mild pain and CSS, demonstrating the need to monitor, address, and treat even non-severe issues in community-dwelling older adults. This association, revealed for the first time in this study, suggests that approaches to reduce pain and CSS are important for maintaining and improving the HRQOL of community-dwelling older adults.

Effects of sleep quality on pain, cognitive factors, central sensitization, and quality of life in patients with chronic low back pain

BACKGROUND

Sleep quality in patients with chronic low back pain (CLBP) may affect quality of life (QoL), possibly due to worsening pain, central sensitization (CS), and cognitive factors. However, causal relationship among the factors has not been confirmed yet.

OBJECTIVE

The purpose of this study was to test the hypothesis that sleep quality in patients with CLBP is attributable to pain, cognitive factors, and CS, and influences QoL, by structural covariance analysis.

METHODS

This is a cross-sectional study. Participants were recruited from six health care facilities and 101 patients with CLBP were included. Structural covariance analysis assessed the fit of data to the model using goodness of fit index (GFI), adjusted goodness of fit index (AGFI), comparative fit index (CFI), and mean squared approximation error (RMSEA).

RESULTS

The structural covariance analysis showed that the goodness-of-fit indices were high (GFI = 0.993, AGFI = 0.964, CFI = 1.00, RMSEA < 0.01). Sleep quality was not directly influenced by QoL but rather by CS and cognitive factors.

CONCLUSION

This study suggests that sleep quality in patients with CLBP is indirectly mediated through multiple pathways, including cognitive factors and CS, which may influence QoL.

Transcranial Direct Current Stimulation Is Safe and Reduces Chronic Fatigue in Patients With Stable Systemic Lupus Erythematosus and Rheumatoid Arthritis

To the best of our knowledge, this is the first case series to assess a combined technique of transcranial direct current stimulation (tDCS - a non-pharmacological and non-invasive brain stimulation) and aerobic exercise in one patient with systemic lupus erythematosus (SLE) and another with rheumatoid arthritis (RA) and significant chronic fatigue. We conducted five sessions of tDCS combined with low-intensity treadmill exercise. Fatigue levels were assessed using the Fatigue Severity Scale and the Visual Analog Scale for fatigue before (pre), immediately after five tDCS sessions (post-zero), and after six months (post-6-mo). The level of fatigue decreased, and functionality improved significantly post-zero and remained sustainable post-6-mo in both SLE and RA cases. There was only one mild and transient side effect (headache) specifically in the patient with RA, and no disease reactivation occurred in any of the cases. Our data showed that tDCS combined with aerobic exercise appears to be safe and promising for reducing fatigue and improving functionality in patients with SLE and RA. Randomized studies with larger sample sizes are required to corroborate our findings.

Investigation of factors influencing low physical activity levels in community-dwelling older adults with chronic pain: a cross-sectional study

Low levels of physical activity in individuals with chronic pain can lead to additional functional impairment and disability. This study aims to investigate the predictors of low physical activity levels in individuals with chronic pain, and to determine the accuracy of the artificial neural network used to analyze these predictors. Community-dwelling older adults with chronic pain (n = 103) were surveyed for their physical activity levels and classified into low, moderate, or high physical activity level groups. Chronic pain-related measurements, physical function assessment, and clinical history, which all influence physical activity, were also taken at the same time. Logistic regression analysis and analysis of multilayer perceptron, an artificial neural network algorithm, were performed. Both analyses revealed that history of falls was a predictor of low levels of physical activity in community-dwelling older adults. Multilayer perceptron analysis was shown to have excellent accuracy. Our results emphasize the importance of fall prevention in improving the physical activity levels of community-dwelling older adults with chronic pain. Future cross-sectional studies should compare multiple analysis methods to show results with improved accuracy.

Dissecting the Molecular Mechanisms Surrounding Post-COVID-19 Syndrome and Neurological Features

Many of the survivors of the novel coronavirus disease (COVID-19) are suffering from persistent symptoms, causing significant morbidity and decreasing their quality of life, termed “post-COVID-19 syndrome” or “long COVID”. Understanding the mechanisms surrounding PCS is vital to developing the diagnosis, biomarkers, and possible treatments. Here, we describe the prevalence and manifestations of PCS, and similarities with previous SARS epidemics. Furthermore, we look at the molecular mechanisms behind the neurological features of PCS, where we highlight important neural mechanisms that may potentially be involved and pharmacologically targeted, such as glutamate reuptake in astrocytes, the role of NMDA receptors and transporters (EAAT2), ROS signaling, astrogliosis triggered by NF-κB signaling, KNDy neurons, and hypothalamic networks involving Kiss1 (a ligand for the G-protein-coupled receptor 54 (GPR54)), among others. We highlight the possible role of reactive gliosis following SARS-CoV-2 CNS injury, as well as the potential role of the hypothalamus network in PCS manifestations.

Effect of central sensitization on dizziness-related symptoms of persistent postural-perceptual dizziness

Background

Persistent postural-perceptual dizziness (PPPD) is a chronic functional dizziness symptom triggered by psychological stress, but its pathophysiology is unknown. Central sensitization is considered the cause of functional diseases, such as medically unexplained symptoms, and is a psychosocially affected condition. However, the association between dizziness symptoms in PPPD and central sensitization remains unclear. Thus, we conducted a cross-sectional study on the relation between dizziness symptoms and central sensitization in PPPD.

Methods

We recruited 61 outpatients with dizziness who met the PPPD diagnostic criteria. In addition to the evaluation of dizziness symptoms using the Dizziness Handicap Inventory, the participants were evaluated using the Hospital Anxiety and Depression Scale, Pittsburgh Sleep Quality Index, and Central Sensitization Inventory (CSI). A CSI score of 40 or higher was defined as central sensitization syndrome (CSS), and the severity of each condition in CSS and non-CSS participants was compared. We also evaluated the association between dizziness symptoms and central sensitization and coexisting symptoms using linear multiple regression analysis.

Results

We analyzed the data of 50 valid responses (valid response rate of 82.0 percent). Compared with the non-CSS group, the CSS group had a higher degree of disability owing to dizziness and a higher rate of complications of anxiety and depression. The regression analysis results showed that the severity of central sensitization was a related factor that could enhance the dizziness symptoms of PPPD.

Conclusions

Central sensitization may affect the dizziness symptoms of PPPD as an exacerbating factor.

The Mediating Effect of Perceived Injustice and Pain Catastrophizing in the Relationship of Pain on Fatigue and Sleep in Breast Cancer Survivors: A Cross-Sectional Study

OBJECTIVE

Multidimensional aspects of pain have raised awareness about cognitive appraisals, such as perceived injustice (PI) and pain catastrophizing (PC). It has been demonstrated that they play an important role in patients' pain experience. However, the mediating effect of these appraisals has not been investigated in breast cancer survivors (BCS), nor have they been related to fatigue and sleep.

METHODS

Cross-sectional data from 128 BCS were analysed by structural path analysis with the aim to examine the mediating effect of PI and PC in the relationship of pain on fatigue and sleep.

RESULTS

The indirect mediating effects of PI on fatigue (CSI*PI = 0.21; P < 0.01 and VAS*PI = 1.19; P < 0.01) and sleep (CSI*PI = 0.31; P < 0.01 and VAS*PI = 1.74; P < 0.01) were found significant for both pain measures (Central Sensitization Inventory (CSI) and Visual Analogue Scale (VAS)). PC, on the other hand, only mediated the relationship between pain measured by VAS and fatigue (VAS*PC = 0.80; P = 0.03). Positive associations were found, indicating that higher pain levels are positively correlated with PI and PC, which go hand in hand with higher levels of fatigue and sleep problems.

CONCLUSION

PI is an important mediator in the relationship of pain on fatigue and sleep, while PC is a mediator on fatigue after cancer treatment. These findings highlight that both appraisals are understudied and open new perspectives regarding treatment strategies in BCS.

Fatigue in Early Rheumatoid Arthritis: Data from the Early Rheumatoid Arthritis Network

OBJECTIVES

Fatigue is a disabling symptom in people with Rheumatoid Arthritis (RA). This study aims to describe the prevalence, risk factors and the longitudinal course of fatigue in early RA.

METHODS

Demographic, clinical, quality of life (QoL), comorbidities and laboratory data were from the Early Rheumatoid Arthritis Network (ERAN), a UK multicentre inception cohort of people with RA.Fatigue was measured using the Vitality subscale of SF36 where higher values represented better QoL. Baseline prevalences of fatigue classifications were age and sex standardised. Linear regression, hierarchical growth curve modelling and group-based trajectory modelling (GBTM) were utilized.

RESULTS

At baseline (n = 1236, 67% female, mean age 57), mean Vitality was 41 (SD ± 11), disease duration 11 months (IQR : 7-18). Age and sex standardized prevalence rates of fatigue and severe fatigue were 44% (CI: 39-50) and 19% (CI: 15-23) respectively.Fatigue changed little over 3 years and 5 measurement occasions, ß=-0.13 (-0.23 to -0.02). GBTM identified 2 sub-groups, which we named 'Fatigue' (53%) and 'No-fatigue' (47%) groups. Female sex, worse pain, mental health, and functional ability were associated with greater fatigue and predicted 'Fatigue' group membership (AUROC = 0.81). Objective measures of inflammation-swollen joint count (SJC) and erythrocyte sedimentation rate (ESR) were not significantly associated with fatigue.

CONCLUSIONS

Fatigue is prevalent and persistent in early RA. Diverse characteristics indicative of central mechanisms are associated with persistent fatigue. Management of fatigue might require interventions targeted at central mechanisms in addition to inflammatory disease modification. People who require such interventions might be identified at presentation with early RA.

Central sensitisation in chronic fatigue syndrome and fibromyalgia; a case control study

INTRODUCTION

Chronic fatigue syndrome (CFS) and fibromyalgia (FM) are both complex conditions that are challenging to treat. This may be related to an incomplete understanding of their pathophysiology, itself obfuscated by their heterogeneity. The symptomatic overlap between them and their common comorbidity suggests a shared vulnerability, which might be explained by central sensitisation.

METHODS

19 CFS cases, 19 FM cases and 20 age and sex matched healthy controls (HC) were recruited primarily from secondary care clinics in London. Those with other pain disorders, psychiatric diagnoses and those taking centrally acting or opiate medications were excluded. Participants were asked to abstain from alcohol and over the counter analgaesia 48 h prior to assessment by static and dynamic quantitative sensory tests, including measures of temporal summation (TS) and conditioned pain modulation (CPM).

RESULTS

CS, as defined by the presence of both enhanced TS and inefficient CPM, was present in 16 (84%) CFS cases, 18 (95%) FM cases, and none of the HC (p < 0.001). Pressure pain thresholds were lower in CFS (Median222kPaIQR 146-311; p = 0.04) and FM cases (Median 189 kPa; IQR 129-272; p = 0.003) compared to HC (Median 311 kPa; IQR 245-377). FM cases differed from HC in cold-induced (FM = 22.6 °C (15.3-27.7) vs HC = 14.2 °C (9.0-20.5); p = 0.01) and heat-induced (FM = 38.0 °C (35.2-44.0) vs HC = 45.3 °C (40.1-46.8); p = 0.03) pain thresholds, where CFS cases did not.

CONCLUSION

Central sensitisation may be a common endophenotype in chronic fatigue syndrome and fibromyalgia. Further research should address whether central sensitisation is a cause or effect of these disorders.

The efficacy of systemic glucocorticosteroids for pain in rheumatoid arthritis: a systematic literature review and meta-analysis

Objectives

Glucocorticosteroids (GCs) are recommended to suppress inflammation in people with active RA. This systematic review and meta-analysis aimed to quantify the effects of systemic GCs on RA pain.

Methods

A systematic literature review of randomized controlled trials (RCTs) in RA comparing systemic GCs to inactive treatment. Three databases were and spontaneous pain and evoked pain outcomes were extracted. Standardized mean differences (SMDs) and mean differences were meta-analysed. Heterogeneity (I², tau statistics) and bias (funnel plot, Egger’s test) were assessed. Subgroup analyses investigated sources of variation. This study was pre-registered (PROSPERO CRD42019111562).

Results

A total of 18 903 titles, 880 abstracts and 226 full texts were assessed. Thirty-three RCTs suitable for the meta-analysis included 3123 participants. Pain scores (spontaneous pain) decreased in participants treated with oral GCs; SMD = −0.65 (15 studies, 95% CI −0.82, −0.49, P <0.001) with significant heterogeneity (I² = 56%, P =0.0002). Efficacy displayed time-related decreases after GC initiation. Mean difference visual analogue scale pain was −15 mm (95% CI −20, −9) greater improvement in GC than control at ≤3 months, −8 mm (95% CI −12, −3) at >3–6 months and −7 mm (95% CI −13, 0) at >6 months. Similar findings were obtained when evoked pain outcomes were examined. Data from five RCTs suggested improvement also in fatigue during GC treatment.

Conclusion

Oral GCs are analgesic in RA. The benefit is greatest shortly after initiation and GCs might not achieve clinically important pain relief beyond 3 months. Treatments other than anti-inflammatory GCs should be considered to reduce the long-term burden of pain in RA.

Central Aspects of Pain in Rheumatoid Arthritis (CAP-RA): protocol for a prospective observational study

BACKGROUND

Pain and fatigue are persistent problems in people with rheumatoid arthritis. Central sensitisation (CS) may contribute to pain and fatigue, even when treatment has controlled inflammatory disease. This study aims to validate a self-report 8-item questionnaire, the Central Aspects of Pain in Rheumatoid Arthritis (CAP-RA) questionnaire, developed to measure central pain mechanisms in RA, and to predict patient outcomes and response to treatment. A secondary objective is to explore mechanisms linking CS, pain and fatigue in people with RA.

METHODS/DESIGN

This is a prospective observational cohort study recruiting 250 adults with active RA in secondary care. The CAP-RA questionnaire, demographic data, medical history, and patient reported outcome measures (PROMs) of traits associated with central sensitization will be collected using validated questionnaires. Quantitative sensory testing modalities of pressure pain detection thresholds, temporal summation and conditioned pain modulation will be indices of central sensitization, and blood markers, swollen joints and ultrasound scans will be indices of inflammation. Primary data collection will be at baseline and 12 weeks. The test-retest reliability of CAP-RA questionnaire will be determined 1 week after the baseline visit. Pain and fatigue data will be collected weekly via text messages for 12 weeks. CAP-RA psychometric properties, and predictive validity for outcomes at 3 months will be evaluated.

DISCUSSION

This study will validate a simple self-report questionnaire against psychophysical indices of central sensitization and patient reported outcome measures of traits associated with CS in a population of individuals with active RA. The application of this instrument in the clinical environment could provide a mechanism-based stratification tool to facilitate the provision of targeted therapy to individuals with pain and fatigue in RA, alongside treatments that target joint inflammation.

TRIAL REGISTRATION

Clinicaltrials.gov NCT04515589 . Date of registration 17 August 2020.

Central Sensitivity and Fibromyalgia

Fibromyalgia presents with symptoms of widespread pain, fatigue, sleeping and cognitive disturbances as well as other somatic symptoms. It often overlaps with other conditions termed 'central sensitivity syndromes' such as irritable bowel syndrome, chronic fatigue syndrome and temporomandibular disorder. Central sensitisation, mediated by amplified processing in the central nervous system, has been identified as the key pathogenic mechanism in these disorders. The term 'central sensitivity' can be used to collectively describe the clinical presentation of these disorders. Fibromyalgia is highly prevalent in most rheumatic diseases as well as non-rheumatic chronic diseases and if unrecognised results in high morbidity. It is diagnosed clinically after excluding important differential diagnoses. Diagnostic criteria have been developed as tools to help identify and diagnose fibromyalgia. Such tools can fulfill an important need when managing patients with rheumatic disease and other chronic diseases as a way to identify fibromyalgia and improve patient outcomes. Treatment involves an integrated approach including education, exercise, stress reduction and pharmacological therapies targeting the central nervous system. This approach is suitable for all presentations of central sensitivity and some central sensitivity syndromes have additional treatment options specific to the clinical presentation. This article is protected by copyright. All rights reserved.

Fatigue in irritable bowel syndrome is associated with plasma levels of TNF-α and mesocorticolimbic connectivity

Irritable bowel syndrome (IBS) is a symptom-based disorder of gut-brain interactions generating abdominal pain. It is also associated with a vulnerability to develop extraintestinal symptoms, with fatigue often reported as one of the most disturbing. Fatigue is related to brain function and inflammation in several disorders, however, the mechanisms of such relations in IBS remain elusive. This study aimed to elucidate fatigue and its association with a resting state network of mesocorticolimbic regions of known importance in fatigue, and to explore the possible role of circulating TNF-α levels in IBS and healthy controls (HC). Resting state functional magnetic resonance imaging (fMRI) was conducted in 88 IBS patients and 47 HC of similar age and gender to investigate functional connectivity between mesocorticolimbic regions. Further, fatigue impact on daily life and plasma levels of the proinflammatory cytokine tumor necrosis factor-α (TNF-α), of known relevance to immune activation in IBS, were also measured. The selected mesocorticolimbic regions indeed formed a functionally connected network in all participants. The nucleus accumbens (NAc), in particular, exhibited functional connectivity to all other regions of interest. In IBS, fatigue impact on daily life was negatively correlated with the connectivity between NAc and dorsolateral prefrontal cortex bilaterally (left p = 0.019; right p = 0.038, corrected for multiple comparisons), while in HC, fatigue impact on daily life was positively correlated to the connectivity between the right NAc and anterior middle insula in both hemispheres (left p = 0.009; right p = 0.011). We found significantly higher levels of TNF-α in IBS patients compared to HC (p = 0.001) as well as a positive correlation between TNF-α and fatigue impact on daily life in IBS patients (rho = 0.25, p = 0.02) but not in HC (rho = -0.13, p = 0.37). There was no association between functional connectivity in the mesocorticolimbic network and plasma levels of TNF-α in either group In summary, this novel multimodal study provides the first evidence that the vulnerability to fatigue in IBS is associated with connectivity within a mesocorticolimbic network as well as immune activation. These findings warrant further investigation, both peripherally and potentially with measurements of central immune activation as well.

Convergent Validity of the Central Sensitization Inventory in Chronic Whiplash-Associated Disorders; Associations with Quantitative Sensory Testing, Pain Intensity, Fatigue, and Psychosocial Factors

OBJECTIVE

Central sensitization is present in different pain conditions, including chronic whiplash-associated disorders. In the absence of a gold standard method of assessment to determine the presence of central sensitization, quantitative sensory testing is currently understood as an optimal proxy. Laboratory sensory testing is, however, not feasible in clinical practice, and the Central Sensitization Inventory was developed as an alternative. The aim of the current study was to evaluate the convergent validity of the Central Sensitization Inventory in chronic whiplash-associated patients by determining the association between the Central Sensitization Inventory and quantitative sensory testing, pain intensity, fatigue, and psychosocial factors.

METHODS

A total of 125 chronic whiplash-associated patients completed multiple questionnaires and were subjected to pressure pain thresholds and temporal summation.

RESULTS

. The Central Sensitization Inventory showed a strong association with constructs of general psychopathology, anxiety, distress, depression, and somatization in chronic whiplash-associated disorders. Moderate correlations were found with fatigue and intrusive and avoidant phenomena after a variety of traumatic events. No significant association was found between the Central Sensitization Inventory and pressure pain thresholds and temporal summation, nor between the Central Sensitization Inventory and other pain measurements.

CONCLUSIONS

Overall, we found that the Central Sensitization Inventory is better in identifying the psychosocial factors related to central sensitization in chronic whiplash-associated disorders than the central nervous system adaptations. Thus, the convergent validity of the Central Sensitization Inventory appears to be only partially present in chronic whiplash-associated disorders.

Fatigue in inflammatory rheumatic disorders: pathophysiological mechanisms

Today, inflammatory rheumatic disorders are effectively treated, but many patients still suffer from residual fatigue. This work presents pathophysiological mechanisms of fatigue. First, cytokines can interfere with neurotransmitter release at the preterminal ending. Second, a long-term increase in serum concentrations of proinflammatory cytokines increase the uptake and breakdown of monoamines (serotonin, noradrenaline and dopamine). Third, chronic inflammation can also decrease monoaminergic neurotransmission via oxidative stress (oxidation of tetrahydrobiopterin [BH4]). Fourth, proinflammatory cytokines increase the level of enzyme indoleamine-2, 3-dioxygenase activity and shunt tryptophan away from the serotonin pathway. Fifth, oxidative stress stimulates astrocytes to inhibit excitatory amino acid transporters. Sixth, astrocytes produce kynurenic acid that acts as an antagonist on the α7-nicotinic acetylcholine receptor to inhibit dopamine release. Jointly, these actions result in increased glutamatergic and decreased monoaminergic neurotransmission. The above-described pathophysiological mechanisms negatively affect brain functioning in areas that are involved in fatigue.

Predictors of fatigue in rheumatoid arthritis

People with RA commonly experience fatigue. Fatigue is a key contributor to increased clinical care costs, primary care consultations and employment loss. Despite this, our understanding of the prognostic of factors of poor fatigue outcomes is lacking and fatigue is poorly managed. Examining longitudinal predictors of fatigue can identify both individuals ‘at risk’ of poor prognosis, and candidate mechanisms that are worthy of greater inspection. This review discusses the factors most commonly investigated as being implicated in the prognosis of RA fatigue. The available data appears to implicate generic factors such as pain, mental health, disability and sleep as consistent predictors of fatigue outcome, while the role of disease activity and inflammation seems less clear. However, the existing data are not without methodological limitations and there have been no specific studies primarily designed to investigate the inflammatory biomarkers of fatigue. Future studies are required to more comprehensively and robustly determine the mechanisms of fatigue.