Dietary Intake of Polyunsaturated Fatty Acids and Pain in Spite of Inflammatory Control Among Methotrexate-Treated Early Rheumatoid Arthritis Patients.

Abstract

ObjectiveTo investigate potential associations between dietary intake of polyunsaturated fatty acids (FAs) and pain patterns in early rheumatoid arthritis (RA) patients after 3 months of methotrexate (MTX) treatment.MethodsWe included 591 early RA patients with MTX monotherapy from a population‐based prospective case–control study, the Epidemiological Investigation of Rheumatoid Arthritis. Dietary data on polyunsaturated FAs (food frequency questionnaires) were linked with data on unacceptable pain (visual analog scale [VAS] >40 mm), noninflammatory/refractory pain (VAS >40 mm and C‐reactive protein [CRP] level <10 mg/liter), and inflammatory pain (VAS >40 mm and CRP level >10 mg/liter) after 3 months. Statistical analysis included logistic regression.ResultsAfter 3 months of MTX treatment, 125 patients (21.2%) had unacceptable pain, of which 92 patients had refractory pain, and 33 patients had inflammatory pain. Omega‐3 FA intake was inversely associated with unacceptable pain and refractory pain (odds ratio [OR] 0.57 [95% confidence interval (95% CI) 0.35–0.95] and OR 0.47 [95% CI 0.26–0.84], respectively). The omega‐6:omega‐3 FA ratio, but not omega‐6 FA alone, was directly associated with unacceptable pain and refractory pain (OR 1.70 [95% CI 1.03–2.82] and OR 2.33 [95% CI 1.28–4.24], respectively). Furthermore, polyunsaturated FAs were not associated with either inflammatory pain or CRP level and erythrocyte sedimentation rate at followup. Omega‐3 FA supplementation was not associated with any pain patterns.ConclusionOmega‐3 FA was inversely associated with, and the omega‐6:omega‐3 FA ratio was directly associated with, unacceptable and refractory pain, but not with inflammatory pain or systemic inflammation. The inverse association between omega‐3 FA and refractory pain may have a role in pain suppression in RA.