Effectiveness of a just-in-time adaptive intervention for improving pain catastrophising in patients with chronic back pain: protocol for a pragmatic randomised controlled trial.

INTRODUCTION: Chronic back pain (CBP), defined as back pain persisting for more than 3 months, is highly prevalent and associated with substantial socioeconomic burden and impaired quality of life. Pain catastrophising is an important cognitive-affective factor in the maintenance of CBP and may fluctuate in daily life. Conventional treatment approaches often do not address these momentary dynamics. Just-in-time adaptive interventions (JITAIs) deliver tailored support at opportune moments based on time-varying information and may therefore complement existing treatments for CBP. In this study, ecological momentary assessment (EMA) is used to capture momentary pain-related states and guide the delivery of adaptive microinterventions. To our knowledge, no JITAI specifically targeting pain catastrophising in CBP has yet been evaluated in a randomised controlled trial. METHODS AND ANALYSIS: This pragmatic, two-arm randomised controlled trial will compare a JITAI with enhanced treatment as usual (TAU+). A total of 100 participants will be recruited to obtain an evaluable sample of 86 participants. Eligible participants are adults with CBP persisting for more than 3 months and an average pain intensity over the previous week of at least 3 on a 0-10 Numerical Rating Scale. Participants in the intervention group will receive app-based, adaptive microinterventions, such as relaxation exercises and physical activities triggered by EMA responses on pain catastrophising and pain intensity. Participants in the TAU+ group complete the same EMA assessments but will not receive adaptive micro-interventions. The primary outcome is reduction in pain catastrophising, assessed with the Pain Catastrophizing Scale. Secondary outcomes include pain intensity, pain interference, pain behaviour, pain quality, physical functioning, anxiety, depression, fatigue, sleep disturbance, social participation, fear-avoidance beliefs, pain-related self-efficacy and treatment satisfaction. Primary and secondary outcomes will be analysed using between-group comparisons according to the intention-to-treat principle. Exploratory analyses will examine proximal, short-term effects of microinterventions using dynamic structural equation modelling. Assessments will be conducted at baseline before randomisation (T0), mid-treatment 2 weeks after intervention start (T1), end of treatment 4 weeks after intervention start (T2) and at 3 months (T3) and 6 months (T4) after end of treatment. ETHICS AND DISSEMINATION: This study has been approved by the Ethics Committee of the Charité Universitätsmedizin Berlin (approval number: EA4/207/21, 18 October 2021). Results will be submitted for publication in peer-reviewed journals and presented at conferences. TRIAL REGISTRATION NUMBER: DRKS00028494.