Treatment targets and outcomes in randomised controlled trials of exercise for non-specific low back pain
Persistent non-specific low back pain (NSLBP) is the leading cause of years lived with disability globally, and exercise is the most widely recommended treatment for persistent NSLBP. Previous randomised controlled trials (RCTs) tend to conclude that, on average, exercise has small to medium effects when benefits, versus comparison arms, are judged using the primary outcomes of pain and function. RCTs should select their primary outcome domain(s) and measure(s) based on the rationale of the treatment(s) they are comparing.
This programme of research aimed to i) identify whether existing RCTs match their primary outcome domains to their specified exercise treatment targets, ii) explore whether better matching of primary outcome domains with exercise treatment targets might change the results and conclusions of existing RCT datasets, iii) compare whether composite outcomes composed of multiple matched outcome domains might change the estimates of the between-arm differences through secondary analysis of existing RCT datasets, and iv) gain stakeholder consensus on the treatment targets of exercise interventions in RCTs of persistent NSLBP.
The systematic review included 27 exercise RCTs that, together, stated 31 treatment targets and included six primary outcome domains. Only 25% of included RCTs had primary outcomes that matched their specified treatment targets. Standardised mean differences (SMDs) of exercise versus comparison arms were larger in the matched (SMD 0.54 (95% CI 0.23 to 0.85), p=0.0006) compared to the unmatched category (SMD 0.22 (95% CI 0.01, 0.44) p=0.04), but this difference was not statistically significant (p=0.10).
Secondary analyses were conducted on a total of nine previous RCT datasets. First, matching was investigated in five RCTs (n=1033) that used an unmatched primary outcome but included some of their matched outcomes as secondary outcomes, and second, by developing composite outcomes in four RCTs (n=864). Firstly, of five RCTs, three had greater SMDs and increased betweenarm statistical significance with matched outcomes compared to an unmatched primary outcome. Of four composite outcomes: three RCTs had greater SMDs and improved statistical precision using the composite outcome compared to the primary outcome in favour of exercise.
Finally, a total of 39 participants contributed to two sequential nominal group consensus workshops. The final prioritised targets of exercise were: improving function, improving quality of life, reducing pain, targeting patient-specific goals, reducing fear of movement and increasing physical activity. This programme of research has highlighted the need for improved identification and specification of treatment targets of exercise interventions for persistent NSLBP. Matching the primary outcome to the treatment targets of the exercise intervention appears to be important, but composite matched outcomes may be more responsive and require further exploration in RCTs of exercise for persistent NSLBP.
|Publicly Available Date||May 30, 2023|