Predictors of change in bodily pain in early rheumatoid arthritis: an inception cohort study.

Objective: To investigate possible predictors for lack of pain improvement after 1 year of treatment for early rheumatoid arthritis (RA).

Methods: The Early Rheumatoid Arthritis Network (ERAN) database was used for analysis of baseline and 1-year pain data. The ERAN is a hospital-based inception cohort of 1,189 people. Short Form 36 questionnaire bodily pain scores were used to calculate change in pain at 1 year as the outcome. The proportion of the Disease Activity Score in 28 joints (DAS28) attributable to patient-reported components (joint tenderness and visual analog scale score; DAS28-P) at baseline was derived as a predictor. Predictors of less improvement in pain were investigated using adjusted odds ratios (OR(adj) ) generated by logistic regression, adjusting for 14 additional clinical and demographic covariates.

Results: Greater pain at baseline was associated with sex, high DAS28, worse mental health, and smoking. Most patients with early RA reported incomplete improvement in bodily pain after 1 year. The DAS28-P index did not significantly change in the patients whose disease remained active. Less improvement in pain was predicted by female sex (OR(adj) 3.41, 95% confidence interval [95% CI] 1.35-8.64) and a high DAS28-P index at baseline (OR(adj) for tertiles 2.09, 95% CI 1.24-3.55). Other conventional RA risk factors did not predict pain changes.

Conclusion: The factors most likely to predict less improvement in pain in early RA are female sex and a high DAS28-P index. A high DAS28-P index may reflect greater contributions of noninflammatory factors, such as central sensitization, to pain. Strategies in addition to inflammatory disease suppression may be required to adequately treat pain.