The association between dietary inflammatory index with risk rheumatoid arthritis: A case-control study.

Diet represents an important set of potential risk factors for rheumatoid arthritis (RA), a known inflammatory condition. This case-control study examined the association between the inflammatory potential of diet, as determined by the dietary inflammatory index (DII®), and RA risk in an Iranian population. The present Case-control study was conducted on 100 RA patients and 200 age- and sex-matched controls in Isfahan, Iran. The presence of RA was determined by expert Rheumatologist assessment based on the American College of Rheumatology definitions. A 168-item food frequency questionnaire was used to collect dietary intake from which DII scores were computed. Odds ratios (OR) and 95 % confidence intervals (CI) for the association between the DII, expressed in tertiles, and RA risk were estimated by two multivariable logistic regression models, one crude model and one in which we controlled for important potential confounders. In the crude model, individuals in the top DII tertile (most pro-inflammatory diet) had more than triple the risk of RA compared to those in the lowest tertile (OR _tertile3vs1 = 3.57; 95 % CI, 1.95-6.53; p< 0.001). The association was essentially unchanged after controlling for potential confounders (OR _tertile3vs1 = 3.83; 95 % CI, 1.66-8.81; p<0.001). We found that a pro-inflammatory diet is associated with increased risk of RA. Higher volume studies are needed to confirm the results.
Competing Interests: Declaration of Competing Interest Dr. James R. Hébert owns controlling interest in Connecting Health Innovations LLC (CHI), a company that has licensed the right to his invention of the dietary inflammatory index (DII®) from the University of South Carolina in order to develop computer and smart phone applications for patient counseling and dietary intervention in clinical settings. Dr. Nitin Shivappa is an employee of CHI. The subject matter of this paper will not have any direct bearing on that work, nor has that activity exerted any influence on this project.
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