The impact of contextual effects in exercise therapy for low back pain: a systematic review and meta-analysis

Abstract

Background

Low back pain is the leading cause of global disability for which exercise therapy is a widely recommended treatment. Research indicates that contextual factors may also influence treatment outcomes in low back pain. Examples include the patient-therapist relationship and other treatment-related circumstances that affect patient expectations. By focusing on the specific treatment effect, clinical trials often ignore the effect of contextual factors, thereby contributing to the so-called efficacy paradox. This means that treatment effects observed in clinical practice are often greater than those reported in clinical trials.

This systematic review aims to investigate the proportion of improvement in pain and disability that can be attributed to contextual effects in the outcome of exercise therapy for patients with low back pain.

Methods

A meta-analysis was conducted. PubMed, Embase, and the Cochrane database were searched for eligible articles reporting randomized controlled trials that compared exercise therapy to placebo interventions. Risk of bias was assessed with the Revised Cochrane Risk of Bias Tool. Outcomes of interest were pain and disability. Meta-analysis was carried out to calculate the proportion attributable to contextual effects for both pain and disability. The body of evidence was assessed using the GRADE methodology.

Results

Eight studies met the inclusion criteria and were included in the meta-analysis. Five studies were rated as having a moderate risk of bias and two studies had a low risk of bias. Proportion attributable to contextual effects was 0.60 (95% CI 0.40–0.89) for pain and 0.69 (95% CI 0.48–1.00) for disability. Certainty of the evidence as assessed with the GRADE methodology was low.

Conclusions

A large extent of pain and disability improvement after exercise therapy in low back pain is attributable to contextual effects although this conclusion is based on low certainty evidence.