Failure to define low back pain as a disease or an episode renders research on causality unsuitable: results of a systematic review

Machine learning-based identification of determinants for rehabilitation success and future healthcare use prevention in patients with high-grade, chronic, nonspecific low back pain: an individual data 7-year follow-up analysis on 154,167 individuals

ABSTRACT

To individually prescribe rehabilitation contents, it is of importance to know and quantify factors for rehabilitation success and the risk for a future healthcare use. The objective of our multivariable prediction model was to determine factors of rehabilitation success and the risk for a future healthcare use in patients with high-grade, chronic low back pain. We included members of the German pension fund who participated from 2012 to 2019 in multimodal medical rehabilitation with physical and psychological treatment strategies because of low back pain (ICD10:M54.5). Candidate prognostic factors for rehabilitation success and for a future healthcare use were identified using Gradient Boosting Machines and Random Forest algorithms in the R-package caret on a 70% training and a 30% test set. We analysed data from 154,167 patients; 8015 with a second medical rehabilitation measure and 5161 who retired because of low back pain within the study period. The root-mean-square errors ranged between 494 (recurrent rehabilitation) and 523 (retirement) days ( R2 = 0.183-0.229), whereas the prediction accuracy ranged between 81.9% for the prediction of the rehabilitation outcome, and 94.8% for the future healthcare use prediction model. Many modifiable prognostic factors (such as duration of the rehabilitation [inverted u-shaped], type of the rehabilitation, and aftercare measure), nonmodifiable prognostic factors (such as sex and age), and disease-specific factors (such as sick leave days before the rehabilitation [linear positive] together with the pain grades) for rehabilitation success were identified. Inpatient medical rehabilitation programmes (3 weeks) may be more effective in preventing a second rehabilitation measure and/or early retirement because of low back pain compared with outpatient rehabilitation programs. Subsequent implementation of additional exercise programmes, cognitive behavioural aftercare treatment, and following scheduled aftercare are likely to be beneficial.

Temporal stability in the prevalence and pattern of co-occurring musculoskeletal pain among people with persistent low back pain: population-based data from the Norwegian HUNT Study, 1995 to 2019

ABSTRACT

People with persistent low back pain (LBP) often report co-occurring persistent musculoskeletal (MSK) pain in other body regions that may influence prognosis as well as treatment approaches and outcomes. This study describes the prevalence and patterns of co-occurring persistent MSK pain among people with persistent LBP based on consecutive cross-sectional studies over 3 decades in the population-based HUNT Study, Norway. The analyses comprised 15,375 participants in HUNT2 (1995-1997), 10,024 in HUNT3 (2006-2008), and 10,647 in HUNT4 (2017-2019) who reported persistent LBP. Overall, ∼90% of participants in each of the HUNT surveys with persistent LBP reported persistent co-occurring MSK pain in other body sites. The age-standardized prevalence of the most common co-occurring MSK pain sites was consistent across the 3 surveys: 64% to 65% report co-occurring neck pain, 62% to 67% report shoulder pain, and 53% to 57% report hip or thigh pain. Using latent class analysis (LCA), we identified 4 distinct patterns of persistent LBP phenotypes that were consistent across the 3 surveys: (1) "LBP only," (2) "LBP with neck or shoulder pain," (3) "LBP with lower extremity or wrist or hand pain," and (4) "LBP with multisite pain," with conditional item response probabilities of 34% to 36%, 30% to 34%, 13% to 17%, and 16% to 20%, respectively. In conclusion, 9 of 10 adults in this Norwegian population with persistent LBP report co-occurring persistent MSK pain, most commonly in the neck, shoulders, and hips or thighs. We identified 4 LCA-derived LBP phenotypes of distinct MSK pain site patterns. In the population, both the prevalence and pattern of co-occurring MSK pain and the distinct phenotypic MSK pain patterns seem stable over decades.

Semi-automated Rasch analysis with differential item functioning

Rasch analysis is a procedure to develop and validate instruments that aim to measure a person's traits. However, manual Rasch analysis is a complex and time-consuming task, even more so when the possibility of differential item functioning (DIF) is taken into consideration. Furthermore, manual Rasch analysis by construction relies on a modeler's subjective choices. As an alternative approach, we introduce a semi-automated procedure that is based on the optimization of a new criterion, called in-plus-out-of-questionnaire log likelihood with differential item functioning (IPOQ-LL-DIF), which extends our previous criterion. We illustrate our procedure on artificially generated data as well as on several real-world datasets containing potential DIF items. On these real-world datasets, our procedure found instruments with similar clinimetric properties as those suggested by experts through manual analyses.

Acute effects of instrument assisted soft tissue mobilization technique on pain and joint position error in individuals with chronic neck pain: a double-blind, randomized controlled trial

PURPOSE/AIM

The aim of this study was to determine the acute effects of IASTM on cervical joint position error and pain in individuals with chronic neck pain.

METHODS

A total of 39 individuals with chronic neck pain were included in this study. Participants were randomized into three groups: Instrument-assisted soft-tissue mobilization(IASTM (n = 13), sham (n = 13), and control (n = 13). In the IASTM group, intervention was applied to the sternocleidomastoid and trapezius muscles with an application time of 45 s and a frequency of 60 beats/min. In the sham group, IASTM was applied at a 90° angle without pressure. The control group did not receive any intervention. The pain severity and joint position error(JPE) were evaluated before and after the intervention, by using the visual analogue scale and a cervical range of motion device.

RESULTS

The effects of time and treatment group on visual analogue scale(VAS) score were statistically significant (p = .001). Instrument-assisted soft-tissue mobilization was more effective in VAS score than sham and control group (p < .001). Significant improvement was found in JPE in all range of motions of the cervical region in the instrument-assisted soft-tissue mobilization group (p < .05). In the sham group, significant improvements were observed in cervical extension, left rotation, and left lateral flexion movements in JPE during each cervical spine active movement (p < .05). Instrument-assisted soft-tissue mobilization group was more effective in JPE all directions than sham and control group.

CONCLUSIONS

Instrument-assisted soft-tissue mobilization may be a useful technique in individuals with chronic neck pain. Instrument-assisted soft-tissue mobilization decreases VAS and improves JPE.

CLINICAL TRIAL REGISTRATION NUMBER

NCT04882397 (05 August 2021).

Guideline-concordant utilization of magnetic resonance imaging in adults receiving chiropractic manipulative therapy vs other care for radicular low back pain: a retrospective cohort study

BACKGROUND

Lumbar magnetic resonance imaging (LMRI) is often performed early in the course of care, which can be discordant with guidelines for non-serious low back pain. Our primary hypothesis was that adults receiving chiropractic spinal manipulative therapy (CSMT) for incident radicular low back pain (rLBP) would have reduced odds of early LMRI over 6-weeks' follow-up compared to those receiving other care (a range of medical care, excluding CSMT). As a secondary hypothesis, CSMT recipients were also expected to have reduced odds of LMRI over 6-months' and 1-years' follow-up.

METHODS

A national 84-million-patient health records database including large academic healthcare organizations (TriNetX) was queried for adults age 20-70 with rLBP newly-diagnosed between January 31, 2012 and January 31, 2022. Receipt or non-receipt of CSMT determined cohort allocation. Patients with prior lumbar imaging and serious pathology within 90 days of diagnosis were excluded. Propensity score matching controlled for variables associated with LMRI utilization (e.g., demographics). Odds ratios (ORs) of LMRI over 6-weeks', 6-months', and 1-years' follow-up after rLBP diagnosis were calculated.

RESULTS

After matching, there were 12,353 patients per cohort (mean age 50 years, 56% female), with a small but statistically significant reduction in odds of early LMRI in the CSMT compared to other care cohort over 6-weeks' follow-up (9%, 10%, OR [95% CI] 0.88 [0.81-0.96] P = 0.0046). There was a small but statistically significant increase in odds of LMRI among patients in the CSMT relative to the other care cohort over 6-months' (12%, 11%, OR [95% CI] 1.10 [1.02-1.19], P < 0.0174) and 1-years' follow-up (14%, 12%, OR [95% CI] 1.21 [1.13-1.31], P < 0.0001).

CONCLUSIONS

These results suggest that patients receiving CSMT for newly-diagnosed rLBP are less likely to receive early LMRI than patients receiving other care. However, CSMT recipients have a small increase in odds of LMRI over the long-term. Both cohorts in this study had a relatively low rate of early LMRI, possibly because the data were derived from academic healthcare organizations. The relationship of these findings to other patient care outcomes and cost should be explored in a future randomized controlled trial.

REGISTRATION

Open Science Framework ( https://osf.io/t9myp ).

Physical Activity is Associated with Less Analgesic Use in Women Reporting Headache-A Cross-Sectional Study of the German Migraine and Headache Society (DMKG)

INTRODUCTION

The aim of this analysis is to determine whether regular physical activity is associated with less analgesic use in men and women suffering from headache disorders based on population-based cross-sectional data.

METHODS

We used data from a random general population sample in Germany that comprised 2477 participants aged ≥ 14 years. A standardized questionnaire addressing headache and headache treatment was filled in during the face-to-face survey.

RESULTS

Thirty-nine percent of the participants reported headache. Of these, 37.5% of men and 33.6% of women were physically active. Of the participants with headache, 43.3% reported taking analgesics on < 2 days a month, 40.7% on 2-5 days a month, 10.1% on 6-10 days a month, and 5.9% on > 10 days a month. Frequent headache, severe impact of headache on daily life, and depressive symptoms were associated with higher analgesic use in both men and women. For women, physical inactivity was associated with the frequency of analgesic use adjusted for sociodemographic and headache-related variables. For men, results did not suggest any association between physical inactivity and frequency of analgesic use.

CONCLUSIONS

There are both sex-unspecific and sex-specific factors associated with analgesic use among men and women with headache. In women with increased analgesic use, promoting physical activity may reduce analgesic use. For men, education about the therapeutic effects of physical activity for headaches is an important resource.

Primary care providers' experiences treating low back pain

CONTEXT

Our original work addresses the biological sex impact on low back pain (LBP) management and prognosis in primary care settings. To our knowledge, our study is the first in the United States to evaluate the differences in clinicians' approaches to LBP in the ambulatory setting specifically based on patient gender. Our findings suggest that there is a knowledge gap among primary care providers (PCPs) toward the potential impact of biological sex on LBP and a bias toward gender roles when counseling patients for home chores or occupational tasks. Further evaluation of this knowledge gap and its impact on LBP management and prognosis is recommended in US healthcare settings.

OBJECTIVES

This study aims to explore PCP experiences and practice patterns regarding LBP in females compared to males in US healthcare settings.

METHODS

We utilized a cross-sectional study design and convenience sampling. Data were collected anonymously utilizing a 27-item online survey sent periodically via email to PCPs working in Ohio. We had 58 responses for analysis; data were analyzed utilizing bivariate and multivariate analyses.

RESULTS

On average, approximately 9 out of 10 responding clinicians reported experiencing LBP. PCPs were not in agreement that LBP is different in women than men. Clinicians with a women's health, osteopathic, or sport's medicine background were more likely to agree that LBP is different in women than in men. PCPs were more likely to counsel female patients about pelvic floor exercises; however, their intake of present pelvic symptoms in LBP female patients is suboptimal. PCPs were more likely to counsel females for home chores than males, which is aligned with the perceived traditional gender roles among PCPs.

CONCLUSIONS

There may be a knowledge gap among PCPs toward the potential impact of biological sex on LBP and a bias toward gender roles when counseling patients for home chores or occupational tasks. Further investigation of this knowledge gap and counseling approaches is recommended to better bridge the gender disparity.

Factors associated with back pain in children aged 6 to 12 years of age, an eight months prospective study

Associated factors of back pain (BP) development before puberty and its persistence are poorly documented. We investigated the association and possible temporality between prior BP history (PBPH), muscular endurance (ME), aerobic capacity (AC), sport activity variables (SAV) and BP in children aged 6 to 12. We collected baseline characteristics (demographics, PBPH, ME, AC and SAV) of children from three primary schools in Canada. Parents replied to weekly text messages regarding their children BP status over an 8-month period. Logistic regression models were adjusted for potential confounders. Data from 242 children (46% female; 8.6 ± 1.7 years) were included. Over the 8-month survey BP prevalence was 48.1%, while the cumulative incidence was 31.9%. The occurrence of at least one BP event was associated with PBPH [OR (IC 95%) = 6.33 (2.35-17.04)] and high AC [2.89 (1.21-6.90)]. High AC was also associated with the development of a first BP episode [2.78 (1.09-7.07)], but ME and SAV were not. BP appears to be relatively common before puberty. BP history seems to be strongly associated with BP recurrence in children. Aerobic capacity is associated with first BP episode development.

Risk factors for non-specific neck pain in young adults. A systematic review

BACKGROUND

Young adulthood is a sensitive period of life where development of musculoskeletal neck pain may be established and impact future health. The objective of this systematic review was to investigate risk factors for non-specific neck pain in young adults.

METHODS

Systematic searches were conducted in six databases in September 2019. Prospective cohorts and registry studies including participants in whom the risk factor or the outcome (neck pain) was registered in the ages 18-29 years old were included. The Quality in Prognosis Studies tool was used for quality assessment. A modification of the Grading of Recommendations Assessments, Development and Evaluation was used to assess the overall quality of the evidence. Potential risk factors investigated in more than one study were summarised.

RESULTS

Searches yielded 4527 articles, of which six matched the eligibility criteria. Fifty-six potential risk factors were investigated in the six studies, covering a broad range of domains. Five risk factors were investigated in more than one study (female sex, body mass index (BMI), physical activity, duration of computer use and perceived stress). Physical activity and BMI showed no association with neck pain, and inconsistent results were found for female sex, duration of daily computer use and perceived stress. Risk of bias was moderate or high in all studies, and the overall quality of evidence was very low.

CONCLUSION

The studies included many potential risk factors, but none of them showed consistent associations with neck pain. There is a paucity of high-quality studies investigating risk factors for neck pain in young adults.

Hospital admission and associated factors among individuals presenting to healthcare facilities for low back pain in Ethiopia

AIM

The aim of this paper is to analyze hospital admission and associated factors following presentation to healthcare facilities for low back pain (LBP) in Ethiopia.

METHODS

A population-based cross-sectional study was conducted between June and November 2018 in South-west Shewa zone of Oromia regional state. Data were collected by face-to-face interviews of adults (≥18 years) with self-reported LBP using a newly developed and validated instrument. All the statistical analyses of (n = 543) individuals with a 1-year history of presentation to healthcare facilities for LBP were performed using R version 3.5.1. The log-binomial regression model was fitted and prevalence ratios with 95% confidence intervals (CIs) were calculated to identify factors associated with hospitalization and the significance level was considered at the P value of ≤ .05.

RESULTS

The proportion of hospital admissions following presentation to healthcare facilities for LBP was 14.4%, 95% CI 11.4-17.3, with an average length of stay (LOS) 7.4 days, 95% CI 6.4-8.8. The admission rate was 18.5%, 95% CI 13.4-23.3 in females and 11.4%, 95% CI 8.0-15.1 in males. Multiple factors, such as gender, age, living conditions, residential environment, alcohol consumption status, intensity of pain, and presence of additional spinal pain, were found to be independently associated with hospitalization for LBP.

CONCLUSIONS

The burden on the individuals and the Ethiopian healthcare system as a result of LBP is evident by the rate of hospital admissions. Further evidence on LBP case referral procedures is needed to allow health policy makers to develop appropriate management strategies capable of dealing with the increasing epidemiology of LBP.

The prognostic merit of self-reported triggers of recurrent low back pain: study protocol

Background

Most cases of low back pain (LBP) are regarded as non-specific and current studies indicate that for many this is a chronic recurrent condition, in which people experience episodes of pain with symptom-free periods in between. It is likely that acute exposure to some factors triggers the reappearance of new episodes in recurrent LBP regardless of the causality of the underlying condition (i.e. risk factors). Additionally, it has been shown that LBP patients present with different trajectories and different trajectories possibly have different triggers. Hence, dividing patients into some clinically meaningful subgroups may offer new insights into triggers, effective preventive strategies and, therefore, prognosis. This study aims to identify self-reported triggers and trajectories of episodes of recurrent LBP and to examine the prognostic association between different triggers and LBP trajectories.

Methods

This is a longitudinal, multicentre, Australia-wide observational study of patients with recurrent non-specific LBP. Two hundred adults with at least a one-year history of LBP will be recruited from primary care clinics or private practices and followed for a year. Each will receive an SMS every fortnight (26 time-points in total) enquiring the occurrence of a new episode of pain in the past 2 weeks and its intensity. Upon report of a new episode, a telephone interview will be performed to appraise exposure to self-nominated triggers in a period of 24 h preceding the pain. Trajectories will be identified by latent class analysis at the end of the follow-up based on the pain intensity, frequency, and length of episodes. Triggers will be categorised into physical and psychosocial groups. Generalised linear mixed models with logit links will be used to explore pain triggers associated with pain trajectories.

Discussion

The completion of this study will provide insight into the patients' self-reported triggers of LBP and also their possible prognostic association with different trajectories. Some newly-identified and pre-identified triggers are likely to be found and reported.

Chronic physical illnesses, mental health disorders, and psychological features as potential risk factors for back pain from childhood to young adulthood: a systematic review with meta-analysis

PURPOSE

To report evidence of chronic physical illnesses, mental health disorders, and psychological features as potential risk factors for back pain in children, adolescents, and young adults.

METHODS

This systematic review and meta-analysis included cohort and inception cohort studies that investigated potential risk factors for back pain in young people. Potential risk factors of interest were chronic physical illnesses, mental health disorders (e.g. depression, anxiety), and other psychological features (e.g. coping, resistance). Searches were conducted in MEDLINE, Embase, CINAHL, and Scopus from inception to July 2019.

RESULTS

Nineteen of 2167 screened articles were included in the qualitative synthesis, and data from 12 articles were included in the meta-analysis. Evidence from inception cohort studies demonstrated psychological distress, emotional coping problems, and somatosensory amplification to be likely risk factors for back pain. Evidence from non-inception cohort studies cannot distinguish between risk factors or back pain triggers. However, we identified several additional factors that were associated with back pain. Specifically, asthma, headaches, abdominal pain, depression, anxiety, conduct problems, somatization, and 'feeling tense' are potential risk factors or triggers for back pain. Results from the meta-analyses demonstrated the most likely risk factors for back pain in young people are psychological distress and emotional coping problems.

CONCLUSION

Psychological features are the most likely risk factors for back pain in young people. Several other factors were associated with back pain, but their potential as risk factors was unclear due to risk of bias. Additional high-quality research is needed to better elucidate these relationships. These slides can be retrieved under Electronic Supplementary Material.

Potential risk factors and triggers for back pain in children and young adults. A scoping review, part I: incident and episodic back pain

Background

The one-month prevalence of back pain in children and adolescents has been reported at 33, 28 and 48% at ages 9, 13 and 15 respectively. There are many suspected risk factors and triggers of back pain in young people.

Objective

The purpose of this scoping review was to identify potential risk factors and potential triggers for back pain in young people. The purpose of part I was to identify potential risk factors for incident and episodic back pain in young people. Part II included all eligible studies with unclear or mixed types of back pain.

Methods

Due to the vast number of studies on "risk factors" for back pain, a two-part scoping review of the literature was chosen as the best way to summarise the evidence. We adhered to the PRISMA-ScR guideline for scoping reviews. General potential risk factors and triggers for back pain in children and young adults (≤ 24 years) were included, incorporating physical, environmental, and/or physiological factors. A search was conducted using PubMed and Cochrane databases from inception to September 2018, limited to the English language. Within part I, and because of their importance, only the results of the studies that investigated risk factors of incident back pain and back pain episodes are presented.

Results

The search identified 7356 articles, of which 91 articles were eligible for this scoping review. The majority of the eligible articles had an unclear definition of back pain (results presented in scoping review part II). There were 7 inception cohort studies included and 1 cohort study that met the criteria for part I. The most consistent risk factors for incident and episodic back pain are female sex and older age.

Conclusion

Due to inconsistent ways of reporting on the type of back pain, no definitive risk factor for back pain has been identified. In general, females often report more symptoms, also for other diseases, and older age is not a useful risk factor as it merely indicates that the onset may not be in childhood. Clearly, the time has come to study the causes of back pain from different angles.

Potential risk factors and triggers for back pain in children and young adults. A scoping review, part II: unclear or mixed types of back pain

Background

Back pain is a global problem in terms of disability and financially, with a large burden both to the individual and to society. Back pain was previously believed to be uncommon in children. However, there is a growing body of evidence that this is not the case.

Objective

Part I of this scoping review studied risk factors of incident and episodic back pain. In this part II we aimed to identify all risk factors and triggers with unclear or mixed type back pain in young people and to identify any gaps in the literature.

Methods

A scoping review design was selected to summarise the evidence, as there are many studies on “risk factors” for back pain. The scoping review followed the PRISMSA-ScR guidelines. We considered all studies that tested potential risk factors and triggers for thoracic and/or lumbar spine pain, in children, adolescents, and young adults (≤ 24 years). PubMed and Cochrane databases were searched from inception to September 2018, to identify relevant English language articles. The results regarding potential risk factors were separated into temporal precursors and bidirectional risk factors and the studies were classified by study design.

Results

Our comprehensive search strategy identified 7356 articles, of which 83 articles were considered eligible for this review (part II). There were 53 cross-sectional studies and 30 cohort studies. Potential risk factors for back pain were: female sex, older age, later pubertal status, positive family history of back pain, increased growth, and a history of back pain, most of which are temporal precursor variables. There was limited research for the illness factors, spinal posture, and muscle endurance in the development of back pain.

Conclusion

Many of the included studies approached risk factors in similar ways and found factors that were associated with back pain but were not obvious risk factors as causality was uncertain. Future research should be more rigorous and innovative in the way that risk factors are considered. This could be through statistical approaches including cumulative exposures, or longitudinal approaches including multi-trajectory methods. Additionally, data on proposed risk factors should be collected before the onset of back pain.

Pubertal development and growth are prospectively associated with spinal pain in young people (CHAMPS study-DK)

PURPOSE

To examine the prospective associations of pubertal development and linear growth with spinal pain frequency and duration in children.

METHODS

We recruited students from 10 public primary schools. Over 42 months, pubertal development was assessed four times and categorized according to Tanner stages 1-5, and height was measured on seven occasions. Occurrences of spinal pain were reported weekly via text messaging. We constructed variables for spinal pain duration (total weeks with pain) and frequency (number of episodes). Potential associations between pubertal development and growth were examined with generalized estimating equations and reported with incident rate ratios (IRRs). All models were adjusted for potential confounders.

RESULTS

Data from 1021 children (53% female; mean [SD] age = 9.4 [1.4] years), with median participation duration of 39 months, were included. Advancing pubertal development was associated with increased spinal pain duration (IRR [95% CI] = 1.90 [1.45, 2.49] to 5.78 [4.03, 8.29]) and frequency of pain episodes (IRR [95% CI] = 1.32 [1.07, 1.65] to 2.99 [2.24, 3.98]). Similar associations were observed for each 1-cm change in height in 6 months with spinal pain duration (IRR [95% CI] = 1.19 [1.15, 1.23]) and frequency (IRR [95% CI] = 1.14 [1.11, 1.17]). The relations between pubertal development and spinal pain, as well as growth and spinal pain, were largely independent.

CONCLUSIONS

In young people, pubertal development and linear growth are likely to be independent risk factors for the development of spinal pain. Pubertal development demonstrates evidence of dose-response in its relationship with spinal pain. This knowledge may assist healthcare providers with clinical decision-making when caring for pediatric patients. These slides can be retrieved under Electronic Supplementary Material.

Can We Trust the Literature on Risk Factors and Triggers for Low Back Pain? A Systematic Review of a Sample of Contemporary Literature

Background

Risk factors (RFs) for the "disease" of low back pain (LBP) are probably different from the triggers of new episodes of LBP. Investigating RFs for the onset of the "disease" and the triggers of LBP is problematic if researchers fail to discern the different types of pain-free status of participants at and before baseline. There is a difference between never having had LBP and having been pain-free for a certain period only. In this review, we assessed the dependability of contemporary literature on RFs and triggers of LBP, in relation to the "disease" and the episodes, respectively.

Methods

A literature search from 2010 until 2017 was performed. Information on the definitions of LBP, potential RFs/triggers, and study design was extracted. Studies were reclassified based on the type of LBP concerning the "disease," episode, or mixed/unclear/chronic. RFs and triggers were grouped into major domains, and positive associations listed, respectively, for the "disease" and episodes.

Results

In 42 of the included 47 articles, it was not clear if the authors investigated RFs for the "disease" of LBP or triggers of new episodes. Only one study properly reported RFs for the onset of the "disease" of LBP, and four studies were deemed suitable to investigate triggers for a new episode of LBP. No study reproduced the results of other included studies.

Conclusion

Trustworthy information regarding RFs and triggers of LBP is rare in the current literature. Future research needs to use precise definitions of LBP (onset of the "disease" vs. episodes) and nominate the timing of the associated factors in relation to the types of LBP as these are two critical factors when studying causes of LBP.