Abstract
ABSTRACT
Background
Chronic pain is a leading cause of disability, yet the longitudinal course of multisite pain—the number of anatomical sites affected—has not been characterised in a nationally representative Asian population. Most prior evidence is cross‐sectional or Western.
Methods
We analysed five waves (2011–2020) of the China Health and Retirement Longitudinal Study, including 23,376 adults aged ≥ 45 years with multisite‐pain data (painful sites, 0–15) in ≥ 2 waves. Trajectories were identified by a single‐stage zero‐inflated Poisson finite‐mixture growth model fitted directly to the repeated counts, with pre‐specified enumeration criteria. Site‐level concordance and baseline factors associated with class membership were also examined.
Results
Five trajectories were identified (APPA 0.74–0.94): persistent minimal (44.9%), low fluctuating (18.6%), low‐rising (16.9%), moderate persistent (10.0%) and high increasing (9.6%); two were non‐monotonic. Among participants reporting pain at consecutive waves, at least one site recurred in 65%–98% of wave pairs, most often the lower back, knees and leg, but the identical site set recurred in fewer than 12%. Higher depressive symptoms (odds ratio per 5 CES‐D‐10 points up to 1.65), greater comorbidity (up to 1.57 per condition), female sex (up to 1.95) and lower education were associated, in a graded manner, with higher‐burden trajectories. Refitting the model with sampling weights reproduced the five‐class structure.
Conclusions
Middle‐aged and older Chinese adults follow heterogeneous, often non‐monotonic multisite‐pain courses, in which a recurring anatomical core is accompanied by movement of pain between sites. Depressive symptoms, multimorbidity, female sex, and lower education mark higher‐burden trajectories.
Significance
Pain‐site counts are widely used as a proxy for pain burden, but whether they track a stable anatomical problem or shifting symptoms has not been shown. Coupling trajectory modelling with site‐level concordance in a national cohort reveals that a rising count reflects accumulation around a recurring low‐back and lower‐limb core rather than migration between unrelated sites, giving the count a concrete anatomical meaning for the first time and supporting its use to stratify risk early, before burden accumulates.