Change over time in functional capacity and self-perceived health status for patients with chronic musculoskeletal pain: a registry-based longitudinal study

BACKGROUND AND AIMS: Chronic musculoskeletal pain is a major public health problem worldwide. Both self-reported functional capacity and self-perceived health status are reduced in patients with chronic musculoskeletal pain. Previous studies mostly assessed functional capacity through self-reported questionnaires instead of objective measurements. The aim of this study, therefore, is to assess the amount of change over time and its clinical meaningfulness in functional capacity and self-perceived health status of patients with chronic musculoskeletal pain undergoing Bern Ambulatory Interprofessional Rehabilitation (BAI-Reha). METHODS: The registry-based longitudinal cohort study with prospectively collected data from a rehabilitation programme took place in a real-life setting. Patients (n = 81) with chronic musculoskeletal pain took part in the BAI-Reha. The main outcomes were the six-minute-walk test (6MWT), the safe maximum floor-to-waist lift (SML) and the European Quality of Life and Health measure visual analogue scale (EQ VAS). Timepoints of measurement were at baseline and post-BAI-Reha (i.e., at 4 months). The quantity of interest was the adjusted time effect (point estimate, 95% confidence interval, and p-value for testing the null hypothesis of no change over time). Statistical significance (a = 0.05) and clinical meaningfulness of the mean value change over time were assessed using pre-defined thresholds (six-minute-walk test 50 m, SML 7 kg, and EQ VAS 10 points). RESULTS: The linear mixed model analysis showed a statistically significant change over time for the six-minute-walk test (mean value change 56.08 m, 95% CI [36.13, 76.03]; p <0.001), SML (mean value change 3.92 kg, 95% CI [2.66, 5.19]; p <0.001), and EQ VAS (mean value change 9.58 points, 95% CI [4.87, 14.28]; p <0.001). Moreover, the improvement in the six-minute-walk test is clinically meaningful (mean value change 56.08 m) and almost clinically meaningful (mean value change 9.58 points) in the EQ VAS. CONCLUSION: Patients walk further, lift more weight, and feel healthier after interprofessional rehabilitation when compared to baseline measurement. These findings confirm and add to previous results. IMPLICATIONS: We encourage other providers of rehabilitation for patients with chronic musculoskeletal pain to measure functional capacity with objective outcome variables and to use self-reported outcome measures in addition to self-perceived health status. The well-established assessments used in this study are suitable for this purpose.