Long-term trajectories of chronic musculoskeletal pain: a 21-year prospective cohort latent class analysis

Our knowledge of the prevalence, impact, and outcomes of chronic pain in the general population is predominantly based on studies over relatively short periods of time. The aim of this study was to identify and describe trajectories of chronic pain status over a period of 21 years. Self-reported population data (n=1858) from five timepoints were analyzed. Pain was categorized by: no chronic pain (NCP); chronic regional pain (CRP); and chronic widespread pain (CWP). Latent Class Growth Analysis was carried out for identification of trajectories, and logistic regression analysis for identification of predictors for pain prognosis. Five trajectories were identified: 1) Persistent NCP (57%); 2) Migrating from NCP to CRP or CWP (5%), 3) Persistent CRP or Migration between CRP and NCP (22%); 4) Migration from CRP to CWP (10%); 5) Persistent CWP (6%). Age, sleeping problems, poor vitality and physical function at baseline were associated with pain progression from NCP. Female gender, seeking care for pain, lack of social support, poor physical function, vitality, and mental health predicted poor pain prognosis among those with CRP. In conclusion chronic pain was common in the population including 6 % reporting persistent CWP, although the majority persistently reported no chronic pain. Most people had stable pain status, but some had ongoing change in pain status over time including people who improved from chronic pain. It was possible to identify clinically relevant factors, characterizing trajectories of chronic pain development, that can be useful for identifying individuals at risk and potential targets for intervention.