ISSLS PRIZE IN CLINICAL SCIENCE 2021: What are the risk factors for low back pain flares and does this depend on how flare is defined?

Association between low back pain and psychological stress response in a Japanese population-based study

BACKGROUND

Psychological stress response refers to the negative emotional states generated when an individual perceives that they do not have the resources to cope with or respond to a threat. Low back pain (LBP) is a complex condition with multiple contributors, including psychological factors. However, whether LBP is a stressor that causes a psychological stress response remains unknown. This study aimed to investigate the association between LBP and psychological stress response in a Japanese population-based cohort.

METHODS

Participants aged >50 years were recruited from inhabitants of a mountain village in Japan. The participants completed the following patient-reported outcome measures. The extent of the psychological stress response was measured using the Stress response scale (SRS)-18, which includes the subscales "Depression/Anxiety", "Irritability/Anger", and "Helplessness". LBP intensity in several situations/positions was measured using a numerical rating scale (NRS). Quality of life (QOL) was measured using the Oswestry Disability Index, EuroQol 5-dimension, and EuroQol visual analog scales. The association between SRS-18 and each parameter was statistically evaluated.

RESULTS

A total of 282 participants (72.1 years old) were analyzed in this study, and 29.1% had chronic LBP. The SRS-18 total score of all participants ranged from 0 to 43, and the average SRS-18 total score was 7.7 ± 8.8 (depression/anxiety: 2.3 ± 3.2, irritability/anger: 2.4 ± 3.3, helplessness: 2.9 ± 3.2). SRS-18 scores of participants with LBP were significantly higher than those of participants without LBP. SRS-18 scores were significantly correlated with QOL scores (P < 0.01, correlation coefficient = 0.22-0.46). Multiple regression analysis showed that the NRS score of LBP during morning awakening was significantly associated with the SRS-18 total, depression/anxiety, and helplessness scores.

CONCLUSIONS

Psychological stress responses were associated with LBP and LBP-related QOL among residents of a Japanese mountain village.

Poor sleep versus exercise: A duel to decide whether pain resolves or persists after injury

Poor sleep is thought to enhance pain via increasing peripheral and/or central sensitization. Aerobic exercise, conversely, relives pain via reducing sensitization, among other mechanisms. This raises two clinical questions: (1) does poor sleep contribute to the transition from acute-to-persistent pain, and (2) can exercise protect against this transition? This study tested these questions and explored underlying mechanisms in a controlled injury model. Twenty-nine adult female Sprague-Dawley rats performed an intensive lever-pulling task for 4 weeks to induce symptoms consistent with clinical acute-onset overuse injury. Rats were then divided into three groups and exposed for 4 weeks to either: voluntary exercise via access to a running wheel, sleep disturbance, or both. Pain-related behaviours (forepaw mechanical sensitivity, reflexive grip strength), systemic levels of brain derived neurotrophic factor (BDNF), estradiol and corticosterone, and white blood cells (WBC) were assessed pre-injury, post-injury and post-intervention. Mechanical sensitivity increased post-injury and remained elevated with sleep disturbance alone, but decreased to pre-injury levels with exercise both with and without sleep disturbance. Reflexive grip strength decreased post-injury but recovered post-intervention-more with exercise than sleep disturbance. BDNF increased with sleep disturbance alone, remained at pre-injury levels with exercise regardless of sleep, and correlated with mechanical sensitivity. WBCs and estradiol increased with exercise alone and together with sleep disturbance, respectively. Corticosterone was not impacted by injury/intervention. Findings provide preliminary evidence for a role of poor sleep in the transition from acute-to-persistent pain, and the potential for aerobic exercise to counter these effects. BDNF might have a role in these relationships.

Differences in risk factors for flare-ups in patients with lumbar radicular pain may depend on the definition of flare

OBJECTIVES

The objective was to determine whether specific physical activity (PA) or psychological stress factors are associated with different definitions of flare-ups (pain-defined flares [PDFs]: periods of increased pain lasting at least 2 h, when pain intensity is distinctly worse than it has been recently; and non-pain-defined flares [NPDFs]: obviously uncomfortable feelings, such as fatigue, loss of function, or emotional/psychosocial fluctuations, without major fluctuations in pain intensity based on 11-point scales) among people with lumbar radicular pain.

METHODS

This was a case-crossover study. Participants with acute or subacute lumbar radicular pain completed serial face-to-face or online assessments for 6 weeks at 3-day intervals to determine whether they experienced sciatica flare-ups (PDF/NPDF) after specific types of PA or psychological stresses.

RESULTS

A total of 152 participants were enroled. There were 597 PDF and 323 NPDF case periods and 800 control periods. The odds of PDFs were increased by prolonged walking and standing, and the odds of NPDFs were increased by prolonged sitting, mental distress, and depressed mood. According to the multivariable analyses, prolonged sitting (OR: 3.0, 95% CI: 1.7-5.5), prolonged walking (OR: 6.2, 95% CI: 3.9-9.9), and prolonged standing (OR: 5.6, 95% CI: 3.3-9.5) were significantly associated with the odds of PDFs, and prolonged sitting (OR: 3.4, 95% CI: 1.8-6.2), mental distress (OR: 6.7, 95% CI: 2.5-17.5), and depressed mood (OR: 5.8, 95% CI: 2.6-12.8) associated with the odds of NPDFs.

CONCLUSIONS

Prolonged sitting, walking, and standing triggered the occurrence of PDF. Prolonged sitting, mental distress, and depressed mood triggered the occurrence of NPDF.

Investigation of the Relevant Factors in the Complexity of Chronic Low Back Pain Patients With a Physiotherapy Prescription: A Network Analysis Approach Comparing Chronic Pain-Free Individuals and Chronic Patients

OBJECTIVE

Chronic low back pain (CLBP) is the leading cause of disability worldwide, and several factors have been proposed as potential causes or cofactors. The aim of this study was to explore their direct and indirect relations to understand CLBP and identify relevant rehabilitation targets.

METHODS

A total of 119 patients with CLBP and 117 chronic pain-free individuals were assessed. A network analysis approach was used to explore the complexity of CLBP by assessing the relations between pain intensity, disability, functionality (physical, social, and psychological), age, body mass index, and education level.

RESULTS

The network analysis revealed the independence of pain and disability related to CLBP from age, sex, and body mass index. Crucially, pain intensity and disability are directly and strongly connected in chronic pain-free individuals, but not in patients with CLBP. Psychosocial functioning is related to pain intensity and disability indirectly through the mediation of one's general health perception and perceived physical functionality.

CONCLUSION

Clinicians should pay more attention to perceived physical functionality and psychosocial factors as they are tightly linked to CLBP. Indeed, pain intensity seems a suboptimal rehabilitation target. This study suggests that a biopsychosocial approach is much needed to investigate CLBP, but it also warns against overestimating the direct impact of each potential contributor.

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CME OBJECTIVES

Upon completion of this article, the reader should be able to: (1) Recognize the relation of pain intensity, disability, and loss of function in patients with CLBP; (2) Determine the impact of the most common biological and psychosocial factors in addressing the assessment of chronic back pain patients; and (3) Enhance confidence in selecting the relevant outcomes for the assessment of patients with CLBP following a multidimensional assessment.

LEVEL

Advanced.

ACCREDITATION

The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™ . Physicians should only claim credit commensurate with the extent of their participation in the activity.

Is it possible to discriminate workers with a higher prevalence of low back pain considering daily exposure time in a work-related lumbar posture? A diagnostic accuracy study

The study aimed to develop and validate a cut-off for daily postures to discriminate workers with low back pain. The self-reported episode of low back pain in the last year and during the previous week and the total spent time in occupational postures of 529 workers were used to screen workers who more likely would report low back pain. The receiver operating characteristics curve verified the ability of daily time in each posture in discriminating workers with low back pain in a training sample. Then, the chi-squared test and measurements of the diagnostic accuracy were performed in the testing sample. The daily time spent in a given posture was not able to accurately discriminate against workers with low back pain. Total time spent walking was the only daily posture that discriminated workers with low back pain in the last year in the testing sample, albeit with low accuracy. Practitioner Summary: The daily time spent in a given posture was not able to accurately distinguish workers with low back pain. Total spent time in walking presented modest diagnostic accuracy and should be interpreted cautiously. The spent time in a particular posture did not detect workers with LBP in the last week.

A vision for the future of wearable sensors in spine care and its challenges: narrative review

OBJECTIVE

This review aimed to: (I) provide a brief overview of some topical areas of current literature regarding applications of wearable sensors in the management of low back pain (LBP); (II) present a vision for a future comprehensive system that integrates wearable sensors to measure multiple parameters in the real world that contributes data to guide treatment selection (aided by artificial intelligence), uses wearables to aid treatment support, adherence and outcome monitoring, and interrogates the response of the individual patient to the prescribed treatment to guide future decision support for other individuals who present with LBP; and (III) consider the challenges that will need to be overcome to make such a system a reality.

BACKGROUND

Advances in wearable sensor technologies are opening new opportunities for the assessment and management of spinal conditions. Although evidence of improvements in outcomes for individuals with LBP from the use of sensors is limited, there is enormous future potential.

METHODS

Narrative review and literature synthesis.

CONCLUSIONS

Substantial research is underway by groups internationally to develop and test elements of this system, to design innovative new sensors that enable recording of new data in new ways, and to fuse data from multiple sources to provide rich information about an individual's experience of LBP. Together this system, incorporating data from wearable sensors has potential to personalise care in ways that were hitherto thought impossible. The potential is high but will require concerted effort to develop and ultimately will need to be feasible and more effective than existing management.

How reliable is measurement of posture during sleep: real-world measurement of body posture and movement during sleep using accelerometers

Objective Understanding sleeping behaviours could improve prevention and treatment of sleep problems and associated health conditions. This study aimed to evaluate a method to assess body posture and movement during sleep using trunk-worn accelerometers for 28 days. Approach Participants (50 adults with low back pain (66% female); aged 32(±9) years) wore two activPAL-micro sensors (thigh, trunk) during their normal daily life for 28 consecutive days. Parameters related to body posture (e.g., time spent lying supine or prone) and movement (e.g., number of turns) during sleep were calculated for each night. Average values for each parameter were identified for different periods, the Spearman-Brown Prophecy Formula was used to estimate the minimum number of nights required to obtain a reliable estimate of each parameter, and repeatability of measures between different weeks was calculated. Main Results Participants spent 8.1(±0.8) hours asleep and most time (44%) was spent in a supine posture. The minimum number of nights required for reliable estimates varied between sleep parameters, range 4-21 nights. The most stable parameters (i.e., requiring less than seven nights) were "average activity", "no. of turns", "time spent prone", and "posture changes in the first hour". Some measures differed substantially between weeks. Significance Most sleep parameters related to body posture and movement require a week or more of monitoring to provide reliable estimates of behaviour over one month. Notably, one week may not reflect behaviour in another week, and the time varying nature of sleep needs to be considered.

Cross-Cultural Adaptation, Reliability, and Psychophysical Validation of the Pain and Sleep Questionnaire Three-Item Index in Finnish

Reciprocal relationships between chronic musculoskeletal pain and various sleep disturbances are well established. The Pain and Sleep Questionnaire three-item index (PSQ-3) is a concise, valid, and reliable patient-reported outcome measure (PROM) that directly evaluates how sleep is affected by chronic low back pain (CLBP). Translation and cross-cultural validation of The Pain and Sleep Questionnaire three-item index Finnish version (PSQ-3-FI) were conducted according to established guidelines. The validation sample was 229 subjects, including 42 pain-free controls and 187 subjects with chronic musculoskeletal pain. Our aims were to evaluate internal consistency, test-retest reliability, measurement error, structural validity, convergent validity, and discriminative validity and, furthermore, to study the relationships between dizziness, postural control on a force plate, and objective sleep quality metrics and total PSQ-3-FI score. The PSQ-3-FI demonstrated good internal consistency, excellent test-retest reliability, and small measurement error. Confirmatory factor analysis confirmed acceptable fit indices to a one-factor model. Convergent validity indicated fair to good correlation with pain history and well-established pain-related PROMs. The PSQ-3-FI total score successfully distinguished between the groups with no pain, single-site pain, and multisite pain. A higher prevalence of dizziness, more impaired postural control, and a general trend towards poorer sleep quality were observed among subjects with higher PSQ-3-FI scores. Postural control instability was more evident in eyes-open tests. The Finnish PSQ-3 translation was successfully cross-culturally adapted and validated. The PSQ-3-FI appears to be a valid and reliable PROM for the Finnish-speaking CLBP population. More widespread implementation of PSQ-3 would lead to better understanding of the direct effects of pain on sleep.

Low Back Pain Flares: How do They Differ From an Increase in Pain?

OBJECTIVE

The term flare is commonly used to describe low back pain (LBP) fluctuations, but individuals with LBP consider that it does not always correspond to increased pain. This case cross-over study aimed to: (1) determine the extent to which days with a flare identified according to a multidimensional definition (self-reported flare, SRF) corresponded to days with greater than average pain (pain-defined flare, PDF) and (2) to investigate whether physical and psychosocial features differ between PDF and SRF.

MATERIALS AND METHODS

Individuals with LBP for ≥3 months (N=126) provided data on flares, physical, and psychosocial features daily for 28 days using a smartphone application.

RESULTS

Most days with SRF (68%) did not have greater than average pain (ie, PDF), but most days with greater than average pain (64%) were reported as an SRF. On days with SRF-only all physical and psychosocial features were worse than nonflare days. SRF+PDF had lower sleep quality and higher pain intensity, fatigue, disability, pain catastrophizing, and fear avoidance than SRF-only. SRF+PDF had higher pain in the afternoon and evening, disability and pain catastrophizing than PDF-only. Self-efficacy at work and during leisure activities was worse on SRF+PDF days than SRF-only and PDF-only days.

DISCUSSION

These findings highlight that when individuals with LBP consider they have a flare, they do not always have greater than average pain, but have worse psychosocial features. This emphasizes that flare has broader dimensions than pain alone. Consideration of flare according to broad dimensions is important when investigating symptom fluctuations across different LBP trajectories.