Research Review By Dr. Shawn Thistle©

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Date Posted:

October 2010

Review Title:

Low Back Pain Updates (written for the Canadian Chiropractic Association’s CCA Report – Fall 2010)

Summary:

As you all know, low back pain (LBP) is a common and costly issue…something we all deal with daily in our offices. Most of the time we achieve successful outcomes using a variety of interventions, but sometimes the course of this condition defies our expectations. This can be frustrating for both doctor and patient.

Research on LBP is rapidly expanding on many fronts – too many to cover in this short article. In this article I thought I would share brief updates on some fundamental research and clinical issues surrounding LBP from 3 recently published papers.

Defining and Predicting Recurrent Low Back Pain

It is well established that a most cases of acute LBP resolve within 4-6 weeks. However, a percentage of patients will become chronic, experiencing recurrent and often progressive episodes. Previous research has indicated that these patients account for a disproportionate amount of healthcare expenditure on LBP, so identifying those at high risk for chronicity is paramount. There are some important issues that arise from this task that will be discussed below.

First, as clinicians turn to the literature for answers, the issue of defining “recurrent low back pain” becomes important. LBP has been extensively studied, yet heterogeneity of patient groups and inconsistency when defining various aspects of LBP have limited the applicability of results. There is controversy on many issues and there is not always a clear answer.

Stanton and colleagues (1) recently investigated, via systematic review, how recurrent LBP has been defined in the literature. Seems simple, right? Well, the results tell us a very different story. After conducting an appropriately structured literature search, 43 studies met inclusion criteria and were analyzed.

To be included, studies had to be written in English, include a study population with non-specific LBP, provide a definition of “recurrent low back pain” and be prospective with a cohort and/or randomized trial design. The majority of studies (27/43 or 63%) did include explicit definitions of recurrent LBP, however:
  • There was a high degree of variation in the definitions used
  • Only 3 definitions were used by more than one study: 1 definition was used in 3 studies, while the other 2 definitions were both used in 2 studies.
  • Several features were commonly seen in the definitions. The most frequent feature present was the frequency of previous episodes of LBP (yet only ~1/3 of the studies included it!) – the problem was that there was large variation within this feature – from “pain twice weekly over a minimum period of 6 months” to “multiple episodes over the past year” to “? 2 episodes of back symptoms in the past year” – a wide range to say the least!
  • Four other features were noted including specifying the number of previous episodes, the duration of pain, the severity of pain and the course of the pain – however these features were not consistently present in the definitions.
  • Only 2 papers included a definition that differentiated between those who had periods of recovery between episodes of LBP and those who have flare-ups but do not fully recover.
It is clear from the results of this study that there is little agreement in the literature on the definition of recurrent LBP. This is problematic, and should be taken into consideration as clinicians interpret and apply the results of studies on LBP populations.

Second, clinicians need to know which factors can help them identify high risk patients during in-office visits. This topic was recently addressed by Chou and Shekelle (2) as they summarized the existing literature (totalling 20 studies) on the usefulness of clinical factors and risk prediction instruments (not discussed here) for identifying those more likely to develop persistent, disabling LBP. Take home points from this study include:
  • The probability of poor outcomes depends in large part on how poor outcomes are defined (similar to the problem outlined above).
  • Age, gender, education level, smoking status and being overweight failed to consistently predict worse outcomes – likelihood ratios (LR) all ~1.
  • The most important predictive factors for poor outcome at 1 year were: presence of non-organic signs (LR 3.0), high levels of maladaptive pain coping behaviours (LR 2.5), high baseline functional impairment (LR 2.1), presence of psychiatric comorbidities (LR 2.2) and low general health status (LR 1.8).
  • Receiving compensation at baseline slightly increases the likelihood of a poor outcome at 1 year - LR 1.4.
  • Higher work dissatisfaction and higher physical demands at work did not predict poor outcomes at 3 months, but did at 1 year (although LRs only 1.5 and 1.4, respectively).
  • The factors that best predict recovery at 1 year are: low levels of fear avoidance (LR 0.39) and low baseline functional impairment (LR 0.40) – results were similar at 3 and 6 months.
  • Variables relating to work environment, baseline pain levels and presence of radiculopathy were less useful for predicting poor outcomes.
Is being overweight correlated with LBP?

The relationship between LBP – both acute and chronic – and being obese or overweight has always been controversial. It makes sense that carrying extra weight, particularly in the abdominal area, could place undue mechanical stress on the low back. The literature on this topic however, is contradictory. Recently, a large study by Heuch et al. (3) presented data from a large cross-sectional, population-based study conducted in Norway – the HUNT study. They aimed to examine the association between body mass index (BMI) and chronic LBP, while adjusting for common confounding factors that may have diluted previous research findings. This paper reported data from over 60 000 subjects (roughly equal numbers of men and women over a range of ages). Pertinent results from this study include:
  • In this sample, 20.9% of men and 26.3% of women experienced chronic LBP (defined as pain in the low back for at least 3 months continuously – see how the issue raised above is so important when attempting to apply research results?).
  • In both genders – a high BMI was correlated significantly with and increased prevalence of LBP.
  • In men, the odds ratio for having chronic LBP for each 5 Kg/m2 increase in BMI was 1.07, in women it was 1.17, after adjustment for age.
  • Adjustment for education, smoking status, leisure/physical activity, employment status and physical activity at work had no major impact on this association (no interactions were noted for any other factors).
Studies like this, to me, are interesting at best. At the end of the day, there numerous benefits to maintaining a healthy weight, and the exact relationship between LBP and obesity should take a back seat to promoting a general approach to good health – including regular exercise and maintaining a healthy weight. We are well positioned to counsel patients on many aspects of health, and should take every opportunity to do so…after all, isn’t that what we say we do?

References:

  1. Stanton TR, Latimer J, Maher CG & Hancock MJ. How do we define the condition “recurrent low back pain”? A systematic review. European Spine Journal 2010; 19: 533-539.
  2. Chou R & Shekelle P. With this patient develop persistent disabling low back pain? JAMA 2010; 303(13): 12-95-1302.
  3. Heuch I, Hagen K, Heuch I et al. The impact of Body Mass Index on the prevalence of low back pain. The HUNT Study. Spine 2010; 35(7): 764-768.