In patients with rheumatoid arthritis (RA) treated with anti-inflammatory medications, long-term persistent pain was found to be common and may be predicted by higher levels of disability and a history of smoking, according to a study published in the Journal of Pain.

The investigators obtained 3-year short-form (SF)-36-Bodily Pain scores from patients with RA receiving treatment in the Early RA Network (n=683), the British Society for Rheumatology Biologics Register Biologics (n=7090), and the non-biologics (n=1720) cohorts. Baseline variables were examined for identified pain trajectories (using SF-36-Bodily Pain scores), and their predictive power for pain trajectories was analyzed using logistic regression. A subgroup analysis of individuals with normal inflammatory markers after 3 years was performed to examine the role of inflammation in this cohort.

Although mean SF-36-Bodily Pain scores were found to improve in each cohort (P <.001 for all), all had scores >1 standard deviation worse than the UK general population. Discrete “persistent pain” (59%-79%) and “resolving pain” (19%-27%) distinct trajectories were identified for each cohort, and the Early RA Network cohort had an additional trajectory with “persistently low pain” (23%). Approximately 65% of patients with normal inflammatory marker levels after 3 years had a “persistent pain” trajectory. Risk factors for “persistent pain” trajectories in each cohort included greater disability (adjusted odds ratio], 2.3-2.5 per unit baseline Health Assessment Questionnaire score) and smoking history (adjusted odds ratio, 1.6-1.8).

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Study limitations include the separate analysis of each cohort and the lack of a pooled meta-analysis to identify consistent patterns in the patient population.

“Persistent pain trajectories cannot be adequately explained by persistent inflammatory disease activity, and this might reflect lifestyle factors or central sensitization, both of which might be amenable to intervention,” the investigators noted. “Identifying subgroups destined to display different pain trajectories should help improve clinical trial design, treatment allocation and, ultimately, pain outcomes for people with RA.”

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McWilliams DF, Dawson O, Young A, Kiely PDW, Ferguson E, Walsh DA. Discrete trajectories of resolving and persistent pain in people with rheumatoid arthritis despite undergoing treatment for inflammation: Results from three UK cohorts [published online January 15, 2019]. J Pain. doi: 10.1016/j.jpain.2019.01.001