Circulating Adipokines in Predicting the Transition from Acute to Persistent Low Back Pain

Sleep as a prognostic factor in low back pain: a systematic review of prospective cohort studies and secondary analyses of randomized controlled trials

Sleep problems are common in individuals with low back pain (LBP) and sleep restriction seems to be associated with impaired pain processing. Our objective was to investigate whether sleep is associated with future LBP outcomes (i.e. pain intensity, disability, and recovery) in adults. We conducted a systematic review of prospective cohort studies and secondary analyses of randomized controlled trials (registration-PROSPERO CRD42022370781). In December 2022, we searched the MEDLINE, Embase, CINAHL, and PsycINFO databases. Fourteen studies, totaling 19 170 participants were included. Thirteen studies were rated as having high risk of bias (QUIPS tool). We used vote-counting and meta-analysis approaches to synthesize the data. We found associations between baseline sleep with future pain intensity, recovery, and between changes in sleep with changes in pain intensity, changes in disability, and recovery. We further synthesized outcomes as "overall LBP improvement" outcomes. Baseline poor sleep was moderately associated with non-improvement in LBP in the long-very long term (OR 1.55, 95% CI: 1.39 to 1.73; three studies providing unadjusted effect sizes), and non-improvement in sleep was largely associated with non-improvement in LBP in the short-moderate term (OR 3.45, 95% CI: 2.54 to 4.69; four studies providing unadjusted effect sizes). We found no association between baseline sleep with future disability and overall LBP improvement in the short-moderate term. Therefore, sleep may be a prognostic factor for pain intensity and recovery from LBP. All findings were supported by low to very low-quality evidence. Better-conducted studies are needed to strengthen our certainty about the evidence.

Characterization of pain-related behaviors in a rat model of acute-to-chronic low back pain: single vs. multi-level disc injury

Introduction

Low back pain is the most common type of chronic pain. We examined pain-related behaviors across 18 weeks in rats that received injury to one or two lumbar intervertebral discs (IVD) to determine if multi-level disc injuries enhance/prolong pain.

Methods

Twenty-three Sprague-Dawley adult female rats were used: 8 received disc puncture (DP) of one lumbar IVD (L5/6, DP-1); 8 received DP of two lumbar IVDs (L4/5 & L5/6, DP-2); 8 underwent sham surgery.

Results

DP-2 rats showed local (low back) sensitivity to pressure at 6- and 12-weeks post-injury, and remote sensitivity to pressure (upper thighs) at 12- and 18-weeks and touch (hind paws) at 6, 12 and 18-weeks. DP-1 rats showed local and remote pressure sensitivity at 12-weeks only (and no tactile sensitivity), relative to Sham DP rats. Both DP groups showed reduced distance traveled during gait testing over multiple weeks, compared to pre-injury; only DP-2 rats showed reduced distance relative to Sham DP rats at 12-weeks. DP-2 rats displayed reduced positive interactions with a novel adult female rat at 3-weeks and hesitation and freezing during gait assays from 6-weeks onwards. At study end (18-weeks), radiological and histological analyses revealed reduced disc height and degeneration of punctured IVDs. Serum BDNF and TNFα levels were higher at 18-weeks in DP-2 rats, relative to Sham DP rats, and levels correlated positively with remote sensitivity in hind paws (tactile) and thighs (pressure).

Discussion

Thus, multi-level disc injuries resulted in earlier, prolonged and greater discomfort locally and remotely, than single-level disc injury. BDNF and TNFα may have contributing roles.

Obesity, Adipokines, and Chronic and Persistent Pain in Rheumatoid Arthritis

We aimed to determine whether adipokines are associated with pain and polysymptomatic distress in patients with rheumatoid arthritis (RA) over time in a large patient registry. The cohort study was conducted in a subset of Forward; a patient-based multi-disease, multipurpose rheumatic disease registry with patients enrolled from community-based rheumatology practices across the U.S. Adipokines (adiponectin, leptin, and fibroblast growth factor[FGF]-21) were measured on stored serum as part of a multi-analyte panel. Body mass index (BMI), pain, polysymptomatic distress, and other patient-reported outcomes (PROs) were reported on biannual questionnaires. Linear regression was used to evaluate independent associations between BMI, adipokines, and PROs. Cox proportional hazards models evaluated independent associations between adipokines and clinically meaningful changes in pain over time (change in numerical rating>1.1 [range 0-10], sustained over 1 year). Among 645 patients included in these analyses, there were significant differences in RA characteristics, comorbidity, PROs, and adipokines across obesity categories. Of note, severely obese patients were more likely to experience greater pain, polysymptomatic distress, and fatigue. Patients with higher FGF-21 levels had higher pain and polysymptomatic stress at baseline, were more likely to use opioids, and were more likely to have sustained worsening pain over time [HR (per 1 SD) (95% CI): 1.22 (1.02,1.46) P = .03] independent of BMI. Obesity and elevated levels of FGF-21 are associated with pain and polysymptomatic distress in RA. Elevated FGF-21 levels may help identify those at risk of worsening pain trajectories over time, independent of BMI. PERSPECTIVE: This study characterizes the relationship between severe obesity and pain and polysymptomatic distress in patients with rheumatoid arthritis and demonstrates that the adipocytokine fibroblast growth factor-21 is independently associated with pain and predicts a worsening trajectory over time. Further mechanistic studies are needed.

Urinary TNF-α as a potential biomarker for chronic primary low back pain

Introduction

Over two thirds of individuals with low back pain (LBP) may experience recurrent or persistent symptoms in the long term. Yet, current data do not allow to predict who will develop chronic low back pain and who will recover from an acute episode. Elevated serum levels of the proinflammatory cytokine tumor necrosis factor-α (TNF-α) have been associated with poor recovery and persistent pain following an acute episode of LBP. Inflammatory cytokines may also mediate mechanisms involved in nociplastic pain, and thus, have significant implications in chronic primary low back pain (CPLBP).

Methods

This study aimed to investigate the potential of urinary TNF-α levels for predicting outcomes and characterizing clinical features of CPLBP patients. Twenty-four patients with CPLBP and 24 sex- and age-matched asymptomatic controls were recruited. Urinary TNF-α concentrations were measured at baseline and after 4 weeks, during which CPLBP patients underwent spinal manipulative therapy (SMT).

Results

Concentrations of TNF-α were found to be elevated in baseline urine samples of CPLBP patients compared to asymptomatic controls. Moreover, these values differed among patients depending on their pain trajectory. Patients with persistent pain showed higher levels of TNF-α, when compared to those with episodic CPLBP. Furthermore, baseline TNF-α concentrations and their changes after 4 weeks predicted alterations in pain intensity and disability following SMT in patients with CPLBP.

Discussion

These findings warrant further research on the potential use of urinary TNF-α concentrations as a prognostic biomarker for CPLBP.

How Do Nonsurgical Interventions Improve Pain and Physical Function in People With Osteoarthritis? A Scoping Review of Mediation Analysis Studies

OBJECTIVE

Nonsurgical interventions are recommended for osteoarthritis (OA). However, how interventions change pain and physical function is unclear. Therefore, the objectives of this scoping review were to 1) identify what potential mediators of nonsurgical interventions on pain and physical function have been evaluated and 2) summarize the findings according to intervention, joint, and outcome.

METHODS

We searched Medline, Embase, CINAHL, Cochrane Central Register of Controlled Trials, and Scopus databases. Studies were included if they conducted a mediation analysis on a randomized controlled trial evaluating a nonsurgical intervention on OA of any joint. Outcomes were pain and physical function.

RESULTS

Nine knee OA studies, evaluating diet plus exercise, exercise, unloading shoes, high-expectation communication during acupuncture, and telephone-based weight loss plus exercise were identified. Except for weight loss and self-efficacy, putative mediators (knee muscle perfusion/extensor strength/adduction moment, systemic inflammatory biomarkers, physical activity, dietary intake, and pain beliefs) were evaluated by single studies. Ten mediators partially mediated intervention (diet plus exercise, exercise, high-expectation communication) effects on pain and physical function. Eight mediators were common to pain and function (reduced weight, increased knee extensor strength, and increased self-efficacy). Constant knee flexor muscle perfusion partially mediated exercise effects on pain, and knee pain relief partially mediated exercise effects on function.

CONCLUSION

In knee OA, some evidence suggests that the benefits of 1) diet and exercise are mediated through changes in body weight, systemic inflammation, and self-efficacy; 2) exercise is mediated through changes in knee muscle strength and self-efficacy; and 3) high-expectation communication style is mediated through changes in self-efficacy.

Immune-inflammatory and hypothalamic-pituitary-adrenal axis biomarkers are altered in patients with non-specific low back pain: A systematic review

This systematic review aimed to investigate immune-inflammatory and hypothalamic-pituitary-adrenal (HPA) axis biomarkers in individuals with non-specific low back pain (NSLBP) compared to healthy control. The search was performed in five databases until 4 November 2021. Two reviewers independently conducted screenings, data extraction, risk of bias, and methodological quality assessment of 14 unique studies. All studies reported the source of the fluid analyzed: nine studies used serum, two used plasma, one used serum and plasma, and two studies used salivary cortisol. We found preliminary and limited evidence (only one study for each biomarker) of increased levels in growth differentiation factor 15 (GDF-15), interleukin-23 (IL-23), transforming growth factor–beta (TGF-β), and soluble tumor necrosis factor receptor 1 (sTNF-R1) in NSLBP. Inconsistent and limited evidence was identified for interleukin-10 (IL-10). Although C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor–alpha (TNF-α) levels appear to increase in NSLBP, only one study per each biomarker reported statistically significant differences. Interleukin-1 beta (IL-1β), interleukin-17 (IL-17), interferon gamma (IFN-γ), and high-sensitivity CRP (hsCRP) showed no significant differences. Regarding cortisol, one study showed a significant increase and another a significant decrease. More robust evidence between GDF-15, IL-23, TGF-β, and sTNF-R1 with NSLBP is needed. Moreover, contrary to the findings reported in previous studies, when comparing results exclusively with healthy control, insufficient robust evidence for IL-6, TNF-α, and CRP was found in NSLBP. In addition, cortisol response (HPA-related biomarker) showed a dysregulated functioning in NSLBP, with incongruent evidence regarding its directionality. Therefore, our effort is to find adjusted evidence to conclude which immune-inflammatory and HPA axis biomarkers are altered in NSLBP and how much their levels are affected.

Association Between Depressive Symptoms or Depression and Health Outcomes for Low Back Pain: a Systematic Review and Meta-analysis

BACKGROUND

Study results vary on whether depressive symptoms are associated with worse prognosis for low back pain (LBP). We assessed the association between depressive symptoms or depression and health outcomes in persons with LBP.

METHODS

We searched MEDLINE, Embase, CINAHL, and PsycINFO from inception to June 2020. Eligible studies were cohort and case-control studies assessing the association between depressive symptoms (questionnaires) or depression (diagnoses) and health outcomes in persons aged ≥16 years with LBP in the absence of major pathology. Reviewers independently screened articles, extracted data, and assessed risk of bias using the Quality in Prognosis Studies tool. We classified exploratory versus confirmatory studies based on phases of prognostic factor investigation. We conducted random-effects meta-analyses and descriptive synthesis where appropriate.

RESULTS

Of 13,221 citations screened, we included 62 studies (63,326 participants; 61 exploratory studies, 1 confirmatory study). For acute LBP, depressive symptoms were associated with self-reported disability (descriptive synthesis: 6 studies), worse recovery (descriptive synthesis: 5 studies), and slower traffic injury-related claim closure (1 study), but not pain or work-related outcomes. Depressive symptoms were associated with greater primary healthcare utilization for acute LBP (1 confirmatory study). For chronic LBP, depressive symptoms were associated with higher pain intensity (descriptive synthesis: 9 studies; meta-analysis: 3 studies, 2902 participants, β=0.11, 95% confidence interval (CI) 0.05-0.17), disability (descriptive synthesis: 6 studies; meta-analysis: 5 studies, 3549 participants, β=0.16, 95% CI 0.04-0.29), and worse recovery (descriptive synthesis: 2 studies; meta-analysis: 2 studies, 13,263 participants, relative risk (RR)=0.91, 95% CI 0.88-0.95), but not incident chronic widespread pain (1 study).

DISCUSSION

Depressive symptoms may be associated with self-reported disability and worse recovery in persons with acute and chronic LBP, and greater primary healthcare utilization for acute LBP. Our review provides high-quality prognostic factor information for LBP. Healthcare delivery that addresses depressive symptoms may improve disability and recovery in persons with LBP. Confirmatory studies are needed to assess the association between depressive symptoms and health outcomes in persons with LBP.

PROTOCOL REGISTRATION

PROSPERO database (CRD42019130047).

Relationship between systemic inflammation and recovery over 12 months after an acute episode of low back pain

BACKGROUND CONTEXT

Individual characteristics can influence outcomes after injury. Our previous work in individuals with early-acute low back pain (LBP) identified subgroups (clusters) with specific biopsychosocial features that recovered poorly or well by 6 months.

PURPOSE

This study extends on that work by revealing the short- and long-term trajectories of recovery and systemic inflammation of these participant clusters: (1) "inflammatory & poor sleep" (Cluster 1), "high TNF & depression" (Cluster 2), "high pain & high pain-related fear" (Cluster 3), and "low pain & low pain-related fear" (Cluster 4).

STUDY DESIGN/SETTING

Longitudinal cohort study.

PATIENT SAMPLE

Eighty-three individuals within 2 weeks of an acute episode of LBP - grouped into their a priori-defined cluster.

OUTCOME MEASURES

General participant characteristics (sex, age, body mass index, smoking history, previous LBP history); self-reported LBP (0-10 numerical rating scale, LBP-related disability (Roland-Morris Disability Questionnaire), depression (Center for Epidemiological Studies Depression Scale, pain catastrophizing (Pain Catastrophizing Scale), fear avoidance (Fear Avoidance Beliefs Questionnaire), pain self-efficacy (Pain Self-Efficacy Questionnaire), and sleep (Pittsburgh Sleep Quality Index); systemic inflammatory biomarkers (C-reactive protein [CRP], interleukin-6 [IL-6], interleukin-1β, tumor necrosis factor [TNF]).

METHODS

Participants provided blood for the measurement of CRP/cytokines, and completed questionnaires related to their pain/disability, psychological and sleep status. Blood measures were repeated 3-monthly for 9 months, and pain/disability were self-reported fortnightly for 12 months. Recovery (change in pain) and CRP/cytokines were longitudinally compared between clusters using mixed-models. Associations between baseline factors and follow-up CRP/cytokines levels were assessed with multiple regression.

RESULTS

Clusters 1 and 2 were associated, but oppositely, with recovery over the 12-months. Cluster 1 reported most recovery at every 3-monthly interval, whereas Cluster 2 reported least recovery. Cluster 1 had elevated CRP (and IL-6) at baseline that continued to decrease from 3 to 9 months. TNF was elevated early and persistently in Cluster 2. Baseline factors other than inflammation generally failed to predict follow-up inflammation.

CONCLUSIONS

Findings support the early role of CRP (and perhaps IL-6) in control of inflammation and recovery, and a pathological role of persistent TNF overexpression, which may be perpetuated by depressive-like behaviors.

Risk factors for low back pain outcome: Does it matter when they are measured?

BACKGROUND

The early identification of factors that increase risk of poor recovery from acute low back pain (LBP) is critical to prevent the transition to chronicity. Although most studies of risk factors for poor outcome in LBP tend to investigate the condition once it is already persistent, there is evidence to suggest that this differs from risk factors measured during the early-acute stage. This study aimed to identify early risk factors for poor outcome in the short- and long-term in individuals with acute LBP, and to compare this with factors identified at 3 months in the same cohort.

METHODS

One hundred and thirty-three individuals were recruited within 2 weeks of an acute LBP episode and completed questionnaires related to their sociodemographic, psychological, clinical and history/treatment status at baseline and 3 months later, and their pain-level fortnightly for 12 months.

RESULTS

Of the 133 participants recruited, follow-up data was provided by 120 at 3 months, 97 at 6 months, 85 at 9 months and 94 at 12 months. Linear regression identified various factors at baseline (acute phase) and 3 months later that predicted short- and long-term outcome (pain level, change in pain). Key findings were that: (1) depressive symptoms at baseline most consistently predicted worse outcome; (2) psychological factors in general at 3 months were more predictive of outcome than when measured at baseline; (3) early health care utilisation predicted better outcome, whereas use of pain medication later (3 months) predicted worse outcome; and (4) sex and BMI predicted outcome inconsistently over 12-months.

CONCLUSIONS

The results highlight the multidimensional nature of risk factors for poor outcome in LBP and the need to consider time variation in these factors.

Does the Interaction between Local and Systemic Inflammation Provide a Link from Psychology and Lifestyle to Tissue Health in Musculoskeletal Conditions?

Musculoskeletal conditions are known to involve biological, psychological, social and, often, lifestyle elements. However, these domains are generally considered in isolation from each other. This siloed approach is unlikely to be adequate to understand the complexity of these conditions and likely explains a major component of the disappointing effects of treatment. This paper presents a hypothesis that aims to provide a foundation to understand the interaction and integration between these domains. We propose a hypothesis that provides a plausible link between psychology and lifestyle factors with tissue level effects (such as connective tissue dysregulation/accumulation) in musculoskeletal conditions that is founded on understanding the molecular basis for interaction between systemic and local inflammation. The hypothesis provides plausible and testable links between mind and body, for which empirical evidence can be found for many aspects. We present this hypothesis from the perspective of connective tissue biology and pathology (fibrosis), the role of inflammation locally (tissue level), and how this inflammation is shaped by systemic inflammation through bidirectional pathways, and various psychological and lifestyle factors via their influence on systemic inflammation. This hypothesis provides a foundation for new consideration of the development and refinement of personalized multidimensional treatments for individuals with musculoskeletal conditions.

Adipokine role in physiopathology of inflammatory and degenerative musculoskeletal diseases

We performed a systematic literature review to summarize the underlying pathogenic mechanisms by which adipokines influence rheumatological diseases and the resulting clinical manifestations. Increasing evidence display that numerous adipokines may significantly influence the development or clinical course of various rheumatological diseases. Despite the normal anti- or pro-inflammatory role of the cytokines, the serum level varies enormously in various rheumatological diseases. The expression of high levels of pro-inflammatory cytokines such as leptin or visfatin, respectively in systemic lupus erythematosus and in rheumatoid arthritis, represents a negative prognostic factor; other adipokines such as adiponectin, broadly known for their anti-inflammatory effects, showed a correlation with disease activity in rheumatoid arthritis. In the near future pro-inflammatory cytokines may represent a potential therapeutic target to restrain the severity of rheumatological diseases. Further studies on adipokines may provide important information on the pathogenesis of these diseases, which are not yet fully understood. The mechanisms by which adipokines induce, worsen, or suppress inflammatory and degenerative musculoskeletal pathologies and their clinical significance will be discussed in this review.

Cohort profile: why do people keep hurting their back?

OBJECTIVE

Low back pain (LBP) is one of the most disabling and costly conditions worldwide. It remains unclear why many individuals experience persistent and recurrent symptoms after an acute episode whereas others do not. A longitudinal cohort study was established to address this problem. We aimed to; (1) evaluate whether promising and potentially modifiable biological, psychological, social and behavioural factors, along with their possible interactions, predict LBP outcome after an acute episode; (2) compare these factors between individuals with and without acute LBP; and (3) evaluate the time-course of changes in these factors from LBP onset. This paper outlines the methodology and compares baseline characteristics between acute LBP and control, and LBP participants with and without follow-up.

RESULTS

133 individuals with acute LBP and 74 pain-free individuals participated. Bio-psycho-social and behavioural measures were collected at baseline and 3-monthly for 12 months (LBP) or 3 months (control). Pain and disability were recorded fortnightly. Baseline characteristics were mostly similar between those who did and did not return for follow-up. Initial analyses of this cohort have revealed important insights into the pathways involved in acute-to-chronic LBP. These and future findings will provide new targets for treatment and prevention of persistent and recurrent LBP.