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

Low-back pain (LBP) is among the most common causes of disability globally with a point prevalence of about 10–30% of the world population, with pain ranging from mild to severe [1‐3]. It is endemic, being reported by about 80% of people at some point in their life [4‐6]. In the Global Burden of Disease study report (GBD 2017), LBP was ranked as the leading cause of disability [7]. Also, for many, LBP is a chronic lifetime condition that imposes a significant burden on them and the health budgets of many countries [8].

The economic burden of chronic LBP such as inpatient or outpatient physical therapy, pharmacy, and work absenteeism is considerable and increasing, and seems to be comparable to the cost of other chronic conditions like heart disease or diabetes [9]. There are numerous treatment options used for LBP, with almost 30% of LBP management costs allocated to physical therapy and medications [10]. However, there is still no over-arching effective treatment of choice for the type of LBP that is described as ‘non-specific’ [11]. It is so called because its aetiology is unknown and, therefore, remains a condition that is difficult to manage for both clinicians and policymakers [12, 13].

It is shown that the natural history of non-specific LBP does not follow precisely an acute, subacute or chronic pattern as described by Nachemson and Bigos back in 1984 [14]. Today, it has been noted that in the general population and primary care setting, low back pain appears to be mostly persistent or recurrent [15]. This manifests as either a persistent episode of pain with different levels of severity (i.e. flare-ups) over a long time or a new episode of pain after a period of being pain-free. Hence, despite common beliefs that LBP is a self-limiting condition, its prognosis is not as favourable as previously believed since it recurs in most instances, and many sufferers experience continuous or multiple episodes of pain in the course of the disease [16‐24].

LBP, in fact, could be compared to other chronic recurrent diseases such as asthma or migraine where it is believed that the ‘disease’ needs to be established first (i.e. the onset of the very first symptoms where one was disease-free/symptom-free previously), followed by episodes of exacerbations later during the course of the disease. Likewise, some people have the ‘disease’ of LBP with many ensuing back pain episodes (exacerbations) throughout their lives [25]. Thus, it is plausible to approach LBP like asthma or migraine in which there is an underlying cause or a number of causes for the ‘disease’ (known as risk factors), while many factors contribute toward its exacerbations (acknowledged as triggers). This concept of an underlying ‘disease’ and consecutive episodes is crucial in the research of episodic, recurring conditions, particularly when risk factors (RFs) are likely to be different from triggers. Consequently, an acknowledgement of a disease-free period and an accurate, precise definition of an episode and non-episode (a pain-free break between two distinct episodes) seems to be indispensable when investigating RFs or triggers of LBP [26].

In 2002, de Vet et al. highlighted the necessity for a clear definition of an episode and non-episode in order to bring unanimity into LBP research and make the interpretation of research findings more tangible [27]. Since they could not find a unanimous definition through a review of the literature, they proposed new definitions for an episode and non-episode following group discussions. This was: “An episode of low back pain is defined as a period of pain in the lower back lasting for more than 24 hours, preceded and followed by a period of at least one month without low back pain”. The proposal was based on what was commonly used in research plus patients’ abilities to recall the pain [27]. However, a relatively recent systematic review of the definition of recurrent low back pain noted that there is still a great diversity in the definition of recurrent LBP [28]. de Vet’s definition can be broken down into two components: 1) definition of pain period (episode) and 2) definition of pain-free period (non-episode). Although the validity of the definition of a non-episode (four weeks pain-free period) was studied in the general population and primary care and shown to be applicable [29, 30], their proposed definition for an episode (a LBP for at least 24 h) has not been scientifically confirmed.

With the Acknowledgement of LBP as an episodic, recurrent disorder, studying its course by just measuring, observing, and reporting on a few episodes or a few points in time at long intervals will not likely reflect the actual long-term course of LBP since data are missed between those measurements. In other words, those discontinuous measurements will not adequately describe the pain profile over time. In this respect, some studies have investigated LBP trajectories and the following points were identified as their major findings:

However, unless the pain trajectories are properly recorded, it would not be possible to investigate if different trajectories have different prognoses, especially following treatment. Additionally, possible associated triggers can be studied and identified when investigating the trajectories of LBP. This potentially allows the specification of those triggers that exacerbate new episodes of pain and possibly cause different types of trajectories. Also, the knowledge of triggers of episodes of LBP could contribute to the effective prevention and self-management opportunity rather than attempting to ‘cure’ the condition.

Steffens et al., in 2014, sought clinicians’ view on short- and long-term triggering factors of a new episode of LBP and found biomechanical factors as the main contributing causes for both. They, however, have only taken the physiotherapists’ point of view into consideration, not those of the patients’ themselves [36].

In 2015, Steffens et al. conducted a case-crossover study, which looked at exposure to some pre-determined factors that they thought might act as triggers of acute episodes of LBP. They reviewed 999 patients who sought care in a primary care setting. Factors that were considered to contribute to the reoccurrence of a new episode were physical factors such as lifting heavy loads, awkward posture, physical activity, and psychosocial factors like alcohol intake and distraction during activity and fatigue. Exposure was measured 2 h, 24–26 h, and 48–50 h prior to the onset of back pain. All physical triggers were significantly associated with an elevated risk of an acute episode of LBP. Fatigue and distraction among psychosocial triggers were also associated with an increased risk of pain. Nevertheless, in this study, the authors only investigated one acute episode of LBP [37]. A secondary analysis of the same study indicated that the patients are reliably capable of identifying their LBP triggering factors [38].

Another study in 2016 compared patients’ and physiotherapists’ views on triggers for LBP. In this study, even though the category of biomechanical factors was identified as the main trigger by both patients and clinicians, there were some dissimilarities in its subcategory. No new factor was identified. Nonetheless, it seems that patients’ views were their general understanding and not episode-specific [39].

Persuasively, it is likely that the outcome will be more plausible and trustworthy in a study where chronic recurrent LBP sufferers are followed for a more extended period, and triggers are identified for every single episode, since the prognostic association between triggers and trajectories may be recognised. Our literature search failed to reveal any study in which the aforementioned methodological strategies were implemented.

This approach may enable clinical scientists to better understand the course of LBP and its relation to triggers. Also, frequent measurements allow researchers to take the number of episodes and their duration into account to accurately define episodes and non-episodes; something that is still lacking in the literature. Another advantage of repeated measurements is to potentially classify patients into appropriate clinical subgroups based on intensity, frequency, and duration of episodes that may suggest a new approach towards triggering factors, prevention, and prognosis.

This is a longitudinal, multicentre, Australia-wide observational study of patients with recurrent non-specific LBP. The study has been approved by the Human Research Ethics Committee at the Murdoch University, Perth, Western Australia (project number 2019/034).

Upon completion of this project, trajectories of LBP in participants with recurrent LBP will be identified and reported. A series of newly identified and pre-identified triggers are likely to be found. Any prognostic association between triggers for the different trajectories will be described as will the association between the trajectories and a series of potential moderators on the assumption that they will differ between trajectory subgroups.

Since no treatment has been found to be significantly superior or even better than placebo in the management of non-specific LBP thus far, it may be useful to consider LBP as a chronic condition with concomitant triggers. Therefore, an effective prevention plan and management opportunity might be achieved by dealing with the LBP triggers and trajectories as this may create the possibility of moving the responsibility of care to the patients using education and secondary prevention. It is predicated on the ability of patients being able to recognise the triggers [38] and these triggers to be avoidable.

It is anticipated that outcome yielded from a study in which chronic recurrent LBP sufferers are followed for a longer period, and triggers are identified for every single episode, would offer more reliable preventive measures, management strategies and understanding of prognosis since the association between trajectories and triggers will be recognised.