Modifiable prognostic factors of high societal costs among people on sick leave due to musculoskeletal disorders: a replication study

Background Musculoskeletal disorders are an extensive burden to society, yet few studies have explored and replicated modifiable prognostic factors associated with high societal costs. This study aimed to replicate previously identified associations between nine modifiable prognostic factors and high societal costs among people on sick leave due to musculoskeletal disorders. Methods Pooled data from a three-arm randomised controlled trial with 6 months of follow-up were used, including 509 participants on sick leave due to musculoskeletal disorders in Norway. Consistent with the identification study, the primary outcome was societal costs dichotomised as high (top 25th percentile) or low. Societal costs included healthcare utilization (primary, secondary, and tertiary care) and productivity loss (absenteeism, work assessment allowance and disability benefits) collected from public records. Binary unadjusted and adjusted logistic regression analyses were used to replicate previously identified associations between each modifiable prognostic factor and having high costs. Results Adjusted for selected covariates, a lower degree of return-to-work expectancy was associated with high societal costs in both the identification and replication sample. Depressive symptoms and health literacy showed no prognostic value in both the identification and replication sample. There were inconsistent results with regards to statistical significance across the identification and replication sample for...