Dietary risk factors for the development of inflammatory polyarthritis: evidence for a role of high level of red meat consumption.

Objective: To investigate the association of red meat and other specific dietary components in predicting the development of inflammatory polyarthritis.
Methods: This nested case-control study was conducted within a prospective population-based study of cancer incidence (European Prospective Investigation of Cancer in Norfolk [EPIC-Norfolk]). EPIC-Norfolk recruited 25,630 subjects ages 45-75 years between 1993 and 1997. Dietary intake was assessed at baseline using a 7-day food diary, and the information was analyzed using dietary analysis software. Patients with new cases of inflammatory polyarthritis were identified by linkage with the Norfolk Arthritis Register, a primary care-based inception study of inflammatory polyarthritis, and were matched for age and sex to 2 controls from EPIC-Norfolk. The risk for development of inflammatory polyarthritis was compared between subjects in the highest and lowest tertiles of dietary intake using conditional logistic regression and was expressed as odds ratios (ORs) with 95% confidence intervals (95% CIs).
Results: Between 1993 and 2002, 88 new patients with inflammatory polyarthritis were identified and matched with 176 controls. Among patients, the level of red meat intake was higher (P = 0.04) and that of vitamin C was lower (P = 0.03) compared with intake among controls, but no difference in total energy intake was observed. Patients were more likely to be smokers. After adjusting for total energy intake, smoking, and other possible dietary confounders, subjects with the highest level of consumption of red meat (OR 1.9, 95% CI 0.9-4.0), meat and meat products combined (OR 2.3, 95% CI 1.1-4.9), and total protein (OR 2.9, 95% CI 1.1-7.5) were at an increased risk for inflammatory polyarthritis.
Conclusion: A high level of red meat consumption may represent a novel risk factor for inflammatory arthritis or may act as a marker for a group of persons with an increased risk from other lifestyle causes.