Abstract
OBJECTIVES: We aimed to determine the degree to which a healthy dietary pattern is associated with incident rheumatoid arthritis (RA). METHODS: We registered this systematic review and meta-analysis in PROSPERO (CRD42025645056). Inclusion criteria were validated diet (anti-inflammatory, Mediterranean, Dietary Approaches to Stop Hypertension (DASH), and/or healthy eating index [HEI]); validated RA definition; dietary exposure preceding RA; and randomized controlled trial, cohort, or case-control design. We searched CENTRAL, Embase, MEDLINE, Scopus, Web of Science, and grey literature as of 2/3/2025. We assessed risk of bias using the Newcastle-Ottawa Scale. Meta-analyses combined adjusted odds ratios (OR) with 95 % confidence interval (CI) for incident RA using random effects models. For heterogeneity, we calculated I(2) and performed subgroup analyses. We assessed certainty of evidence using GRADE. RESULTS: We included 12 case-control and cohort studies (8 of which were independent) in the review. Three studies were low risk of bias, 3 moderate, 3 high, and 3 very high. Healthy overall dietary pattern was associated with lower risk of incident RA (OR 0.54, 95 % CI 0.32-0.91, I(2)=81 %). Including only studies with the lowest risk of bias was also associated with lower RA risk (OR 0.84, 95 % CI 0.76-0.94, I(2)=0 %). Anti-inflammatory (OR 0.56, 95 % CI 0.31-0.99), Mediterranean (OR 0.88, 95 % CI 0.78-0.99), and HEI (OR 0.60, 95 % CI 0.25-1.47) patterns all showed lower point estimates for RA. Overall level of certainty in these results was moderate due to the studies' observational nature. CONCLUSIONS: In observational studies, healthy dietary pattern is associated with reduced risk of incident RA.