Pain trajectories in relation to incident functional limitation among older adults: A prospective cohort study

OBJECTIVES: We aimed to identify pain trajectories and examine their associations with incident functional limitation in older adults, including activities of daily living (ADL) and instrumental ADL (IADL). DESIGN: A prospective cohort study. SETTING: Community-based setting in western China. PARTICIPANTS: We included participants with pain score information during 2018-2022, no prevalent functional limitation by 2022, and sufficient follow-up data for functional limitation assessment during 2023-2024. MEASUREMENTS: Group-based trajectory modeling was applied to identify pain trajectories based on the Numeric Rating Scale pain scores. Multivariate logistic regression models were used to assess the association between pain trajectories and incident ADL and IADL limitation. Sensitivity analyses were conducted using generalized estimating equations. Subgroup analyses were performed to assess potential interaction effects. RESULTS: A total of 887 older adults (all aged ≥60 years) were finally included in the analytic sample, of whom 139 (15.7%) and 198 (22.3%) individuals developed incident ADL and IADL limitation during the two-year follow-up, respectively. Four pain trajectories were identified: 'Persistently Pain-Free' (43.0%), 'Pain Remission' (16.7%), 'Developing Mild Pain' (21.9%), and 'Persistent Mild-to-Moderate Pain' (18.5%). Compared to the 'Persistently Pain-Free' group, only participants in the 'Persistent Mild-to-Moderate Pain' group had a significantly higher risk of developing ADL limitation (adjusted odds ratio = 2.19, 95% CI 1.32-3.63). No significant associations were found between any pain trajectory and the risk of incident IADL limitation. No significant interactions were observed in the subgroup analyses for either ADL or IADL (P for interaction > 0.05). CONCLUSION: Persistent pain, even at mild-to-moderate levels, independently predicts incident limitation in ADL rather than IADL in older adults, while achieving pain remission may help prevent functional decline in ADL. These findings underscore the importance of early identification and management of persistent pain to help maintain functional independence.