Relative contributions of the nervous system, spinal tissue and psychosocial health to non-specific low back pain: Multivariate meta-analysis.

BACKGROUND AND OBJECTIVES: Nervous system, psychosocial and spinal tissue biomarkers are associated with non-specific low back pain (nsLBP), though relative contributions are unclear. DATABASES AND DATA TREATMENT: MEDLINE, EMBASE, CINAHL, PsycINFO and SPORTDiscus were searched up to 25 March 2020. Related reviews and reference lists were also screened. Observational studies examining structural and functional nervous system biomarkers (e.g. quantitative sensory tests, structural and functional brain measures), psychosocial factors (e.g. mental health, catastrophizing) and structural spinal imaging biomarkers (e.g. intervertebral disc degeneration, paraspinal muscle size) between nsLBP and pain-free controls were included. For multivariate meta-analysis, two of three domains were required in each study. Random-effects pairwise and multivariate meta-analyses were performed. GRADE approach assessed evidence certainty. Newcastle-Ottawa scale assessed risk of bias. Main outcomes were the effect size difference of domains between nsLBP and pain-free controls. RESULTS: Of 4519 unique records identified, 33 studies (LBP = 1552, referents = 1322) were meta-analysed. Psychosocial state (Hedges' g [95%CI]: 0.90 [0.69-1.10], p < 0.001) in nsLBP showed larger effect sizes than nervous system (0.31 [0.13-0.49], p < 0.001; difference: 0.61 [0.36-0.86], p < 0.001) and spine imaging biomarkers (0.55 [0.37-0.73], p < 0.001; difference: 0.36 [0.04-0.67], p = 0.027). The relationship between domains changes depending on if pain duration is acute or chronic. CONCLUSIONS: Psychosocial effect sizes in nsLBP are greater than those for spinal imaging and nervous system biomarkers. Limitations include cross-sectional design of studies included and inference of causality. Future research should investigate the clinical relevance of these effect size differences in relation to pain intensity and disability. STUDY REGISTRATION: PROSPERO-CRD42020159188. SIGNIFICANCE: Spinal structural lesions (e.g. intervertebral disc degeneration), psychosocial (e.g. depression) and nervous system factors (detected by e.g. quantitative sensory tests, structural and functional measures) contribute to non-specific low back pain. However, psychosocial factors may be more compromised than nervous system and spinal imaging biomarkers. This relationship depends on if the pain is acute or chronic. These findings underscore that the 'non-specific' label in back pain should be reconsidered, and more specific multidimensional categories evaluated to guide patient management.

Examining resting-state functional connectivity in key hubs of the default mode network in chronic low back pain.

OBJECTIVES: Changes in brain connectivity have been observed within the default mode network (DMN) in chronic low back pain (CLBP), however the extent of these disruptions and how they may be related to CLBP requires further examination. While studies using seed-based analysis have found disrupted functional connectivity in the medial prefrontal cortex (mPFC), a major hub of the DMN, limited studies have investigated other equally important hubs, such as the posterior cingulate cortex (PCC) in CLBP. METHODS: This preliminary study comprised 12 individuals with CLBP and 12 healthy controls who completed a resting-state functional magnetic resonance imaging (fMRI) scan. The mPFC and PCC were used as seeds to assess functional connectivity. RESULTS: Both groups displayed similar patterns of DMN connectivity, however group comparisons showed that CLBP group had reduced connectivity between the PCC and angular gyrus compared to healthy controls. An exploratory analysis examined whether the alterations observed in mPFC and PCC connectivity were related to pain catastrophizing in CLBP, but no significant associations were observed. CONCLUSIONS: These results may suggest alterations in the PCC are apparent in CLBP, however, the impact and functional role of these disruptions require further investigation.

Neural activity during cognitive reappraisal in chronic low back pain: a preliminary study.

OBJECTIVES: Chronic pain patients often report higher levels of negative emotions, suggesting reduced ability to regulate emotions effectively, however, little is known of the underlying neural cognitive mechanisms. Therefore, the aim of this study was to explore brain activity and connectivity during cognitive reappraisal in chronic low back pain (CLBP). METHODS: This study recruited 24 female participants; 12 with CLBP and 12 healthy controls. Participants completed an emotion regulation task that involved cognitive reappraisal of negative images during functional magnetic resonance imaging. The negative affect following each image and perceived success of the task were reported. Region of interest and seed-to-voxel analyses were conducted using key regions involved in cognitive reappraisal (i.e., amygdalae and dorsomedial prefrontal cortex) as seed regions. RESULTS: During the task, there were no group differences in the behavioural measures and blood oxygen level-dependent (BOLD) brain activation in the seed regions. Functional connectivity analysis showed reduced coupling between the amygdalae and dorsolateral prefrontal cortex, orbitofrontal cortex and inferior parietal cortex in the CLBP group compared to controls. Connectivity between the amygdala and inferior parietal cortex positively correlated with the percent of reduced negative affect during reappraisal in the CLBP group. CONCLUSIONS: These preliminary findings demonstrate that individuals with CLBP exhibit similar emotion regulation abilities to healthy controls at the behavioural and BOLD level. However, altered functional connectivity observed in the CLBP group may reduce effective cognitive reappraisal. These results provide evidence for the potential clinical impact of network changes in CLBP.

Poor general health and lower levels of vitality are associated with persistent, high-intensity low back pain and disability in community-based women: A prospective cohort study.

While low back pain significantly impacts on an individual's well-being, our understanding of the role of well-being in the natural history of low back pain is limited. This cohort study aimed to investigate the association between psychological and general well-being and the development and progression of low back pain and disability in community-based women over a 2-year period. 506 women recruited from a research database were invited to participate. Overall psychological and general well-being and its subdomains were assessed at baseline using the Psychological General Well-Being Index (PGWB). The intensity of and degree of disability arising from low back pain were examined using the Chronic Pain Grade Questionnaire at baseline and at 2-year follow-up. Participants were categorized as having no, developing, resolving, or persistent high-intensity pain and disability. 444 participants (87.8%) completed the study. Women with persistent high-intensity pain had lower PGWB scores at baseline than those with no high-intensity pain at follow-up, after adjusting for confounders (M(SE) = 69.9(2.55) vs 80.1(2.63), p < 0.005). Furthermore, women with persistent high disability scores had lower well-being scores than those without persistent high disability scores (M(SE) = 69.1(3.49) vs. 81.2(0.802), p = 0.001). Moreover, lower scores in the well-being subdomains of general health and vitality were associated with persistent high pain intensity and disability (all p < 0.007). In summary, lower levels of general health and vitality were associated with persistent high-intensity low back pain and disability, suggesting that improving these aspects of well-being has the potential to reduce high levels of chronic low back pain and disability in community-based women.

A Systematic Review of the Processes Underlying the Main and the Buffering Effect of Social Support on the Experience of Pain.

OBJECTIVE: This review aimed to explore the processes that underlie the main and the buffering effect of social support on decreased pain experience. MATERIALS AND METHODS: The systematic review was conducted according to the PRISMA guidelines. Online databases of PubMed and PsycINFO were searched for peer-reviewed articles using keywords ("social support," OR "interpersonal," OR "social presence," OR "spouse," OR "couple," OR "marriage") AND "pain"). Articles were included if they examined the cognitive or behavioral processes linking social support to any aspects of reduced pain experience. RESULTS: The database search identified 38 studies, of which 33 were cognitive-behavioral studies and 5 were neurobiological. Cognitive-behavioral studies generated a total of 57 findings of the analgesic influence of social support. This effect was further categorized as social support decreasing the adverse influence of pain-related stress (28/44 findings), reappraising pain-related stress (7/9 findings), and facilitating coping attempts (2/4 findings). Of the 5 neurobiological studies, the influence of social support on pain reduction was associated with reduced neural and physiological stress systems in response to painful stimuli. DISCUSSION: This review presents evidence that the stress-buffering effect is more often able to account for the relationship between social support and pain experience. Moreover, findings suggest the critical significance of stress appraisal and attenuated stress systems in linking social support to aspects of reduced pain experience. Findings implicate the role of integrating perceived support and intimacy in support-oriented interventional trials for chronic pain.

The Relationship Between Structural and Functional Brain Changes and Altered Emotion and Cognition in Chronic Low Back Pain Brain Changes: A Systematic Review of MRI and fMRI Studies.

OBJECTIVES: Chronic low back pain (CLBP) is a major health issue, yet its underlying mechanisms remain unknown. Studies have demonstrated the importance of emotion and cognition in chronic pain; however, the relevant brain physiology in magnetic resonance imaging (MRI) studies are unclear in CLBP populations. Therefore, this review aimed to identify MRI brain changes and examine their potential relationship with emotional and cognitive processes in CLBP. METHODS: A systematic search was conducted in 5 databases. Studies that recruited adult, CLBP populations, and used brain MRI protocols were included. RESULTS: In total, 55 studies met the inclusion criteria. Of the structural MRI studies, 10 of 15 studies found decreased gray matter and 7 of 8 studies found white matter changes in CLBP groups compared with controls. Fourteen resting-state functional MRI studies all reported differences between CLBP and control groups in the default mode network. Interestingly, only 3 of 10 functional MRI studies observed significant differences during noxious stimulation between CLBP and control groups, whereas 13 of 16 studies observed significant brain activation differences in CLBP groups during various external tasks. Finally, there were 3 studies that observed a degree of recovery in functional connectivity following intervention. DISCUSSION: The brain changes in CLBP groups were mainly observed in areas and networks important in emotion and cognition, rather than those typically associated with nociception. This supports the understanding that emotional and cognitive processes may be the core contributor to the CLBP experience; however, future studies need to explore these processes further.

Negative beliefs about low back pain are associated with persistent high intensity low back pain.

While previous cross-sectional studies have found that negative beliefs about low back pain are associated with pain intensity, the relationship between back beliefs and persistent low back pain is not well understood. This cohort study aimed to examine the role of back beliefs in persistent low back pain in community-based individuals. A hundred and ninety-two participants from a previous musculoskeletal health study were invited to take part in a two-year follow-up study. Beliefs about back pain were assessed by the Back Beliefs Questionnaire (BBQ) at baseline and low back pain intensity was measured by the Chronic Pain Grade Questionnaire at baseline and follow-up. Of the 150 respondents (78.1%), 16 (10.7%) reported persistent high intensity low back pain, 12 (8.0%) developed high intensity low back pain, in 16 (10.7%) their high intensity low back pain resolved and 106 (70.7%) experienced no high intensity low back pain. While participants were generally positive about low back pain (BBQ mean (SD) = 30.2 (6.4)), those with persistent high intensity pain reported greater negativity (BBQ mean (SD) = 22.6 (4.9)). Negative beliefs about back pain were associated with persistent high intensity low back pain after adjusting for confounders (M (SE) = 23.5 (1.6) vs. >30.1 (1.7), p < .001). This study found negative back beliefs were associated with persistent high intensity low back pain over 2 years in community-based individuals. While further longitudinal studies are required, these findings suggest that targeting beliefs in programs designed to treat and prevent persistent high intensity low back pain may be important.