Effectiveness and cost-effectiveness of a progressive, individualised walking and education program for prevention of low back pain recurrence in adults: statistical analysis plan for the WalkBack randomised controlled trial

Exercise for the prevention of low back pain recurrences is recommended, but under-researched. The effectiveness and cost-effectiveness of a walking program for preventing low back pain recurrence remains unknown. This a priori statistical analysis plan describes the methods of analysis for the WalkBack trial. WalkBack is a prospectively registered, pragmatic, randomised controlled trial. The aim is to investigate the effectiveness and cost-effectiveness of a 6-month progressive and individualised walking and education program (intervention) for the prevention of low back pain recurrences, compared to a no-treatment control group. The primary outcome is days to the first recurrence of an episode of activity-limiting low back pain. Key secondary outcomes include days to any recurrence of low back pain, days to a care-seeking recurrence of low back pain, disability level, health-related quality of life, costs associated with low back pain and adverse events. All participants will be followed for a minimum of 12 months. Analysis will follow the intention-to-treat principle. Cox regression is planned to assess the effects for the outcomes of time to activity-limiting, minimal and care-seeking recurrence. Hazard ratios and median survival times with 95% confidence intervals will be calculated. The effect of the intervention on continuous outcomes will be estimated with repeated-measure linear mixed models. An economic evaluation will be performed from the societal perspective for recurrence prevented (yes/no) and quality-adjusted life years. The proportion of adverse events between groups will be compared using Fisher's exact test. The WalkBack trial will provide evidence on the effectiveness and cost-effectiveness of a walking intervention to prevent low back pain recurrences. This statistical analysis plan provides transparency on the analysis of the trial. WalkBack - Effectiveness and cost-effectiveness of a progressive individualised walking and education program for the prevention of a recurrence of low back pain. ACTRN12619001134112 . Date Registered: 14/08/2019.