Mediators of Treatment Effect in the Back In Action Trial

Abstract

Objectives: To test whether change in fear-avoidance beliefs was a mediator of the effect of treatment on disability outcome, and to test an analytical approach, latent growth modeling, not often applied to mediation analysis.Methods: Secondary analysis was carried out on a randomized controlled trial designed to compare an intervention addressing fear-avoidance beliefs (n = 119) with treatment as usual (n = 121) for patients with low back pain, which found the intervention to be effective. Latent growth modelling was used to perform a mediation analysis on the trial data to assess the role of change in fearavoidance beliefs on disability outcome. The product of coefficients with bias-corrected bootstrapped confidence intervals was used to calculate the mediating effect.Results: A statistically significant mediating effect of fear-avoidance beliefs on the effect of treatment on disability outcome was found (standardized indirect effect À0.35; bias-corrected 95% CI, À 0.47 to À 0.24). Poor fit of the model to the data suggested that other factors not accounted for in this model are likely to be part of the same mediating pathway.Discussion: Fear-avoidance beliefs were found to mediate the effect of treatment on disability outcome. Measurement of all potential mediator variables in future studies would help to more strongly identify which factors explain observed treatment effects. Latent growth modelling was found to be a useful technique to apply to studies of treatment mediation, suggesting that future studies could use this approach.Key Words: mediation analysis, latent growth modeling, low back pain (Clin J Pain 2017;33:811-819) W orldwide, the prevalence of low back pain (LBP) has been estimated to be 9.4% (95% confidence interval [CI], 9.0-9.8), 1 with lifetime prevalence estimates of between 51% and 84%. 2 In the UK, LBP has been found to affect between 49% and 80% of the population at some point in their lifetime, leading to high costs in terms of health care, workplace absence, 3 and impact on individual quality of life. 4 In the UK, musculoskeletal (MSK) conditions are predominantly managed in primary care, with back pain being the most common reason for patient health care visits. 5 Although the prognosis of patients with an acute episode of LBP is often good, 6,7 prognosis varies substantially for individual patients 8 and persisting symptoms are reported by many patients up to a year after their initial consultation. 6,8 Psychological factors (eg, fear-avoidance behaviors and beliefs, 9-17 catastrophizing thoughts, 9,18 self-efficacy, 9,19 and depression 9,11,14,20 ) have been found to be strong predictors of LBP outcomes and evidence suggests that they are potentially important in influencing the effect of treatment. Guidelines on the management of LBP also recommend screening for and management of psychological factors. 21,22 However, it remains unclear how interventions addressing psychological factors improve patient outcomes, 23 with mixed results being found in primary care populations in pa...

Sleep and Pain

“…The studies that provide the richest data apply microlongitudinal designs using ecological momentary assessment, thereby allowing within-person variations in a range of symptoms to be examined, as well as adjustment for person-level variables. Combined with multilevel and latent growth curve modeling approaches,60 these methods hold much promise to address questions of causal mediation.…”

Supporting self-management of low back pain with an internet intervention in primary care: a protocol for a randomised controlled trial of clinical and cost-effectiveness (SupportBack 2)

“…We will also explore the potential of multilevel modelling to examine mediating variables association with the outcome over time. 39 Appropriate checks of the assumptions of causal modelling, such as exchangeability (no confounding), consistency, effect modification and temporality will also be carried out. 40 41 …”

“…We will also explore the potential of multilevel modelling to examine mediating variables association with the outcome over time. 39 Appropriate checks of the assumptions of causal modelling, such as exchangeability (no confounding), consistency, effect modification and temporality will also be carried out. 40 41 Questions will be included in the qualitative interviews focusing on participants' perceptions of how use of the SupportBack intervention and/or telephone support affected their LBP.…”

Understanding the mechanisms of a combined physical and psychological intervention for people with neurogenic claudication: protocol for a causal mediation analysis of the BOOST trial

“…[44][45][46][47][48][49][50][51][52][53] While cognitive behavioural approaches have not been well investigated in people with LSS, 54 this is an important component of the BOOST intervention based on evidence that addressing unhelpful beliefs and behaviours can mediate changes in both disability and symptom severity in low back pain populations. [55][56][57][58][59][60] In addition, self-efficacy is likely to play a role in mediating disability, physical function and activity in older adults with chronic musculoskeletal conditions. [61][62][63] Alternative mediators that we will include in our causal mediation models, therefore, include physical function (SPPB), physical activity (RADI), fear-avoidance behaviour (FABQ) and walking self-efficacy (GES).…”