Association of ultraprocessed food consumption with risk of rheumatoid arthritis: a retrospective cohort study in the UK Biobank

Background: Limited studies explored the association between consumption of ultraprocessed food (UPF) and rheumatoid arthritis (RA). Objectives: This study aimed to examine the association between UPF consumption and RA risk and explore the potential mediating effects of RA- related biomarkers. Methods: This retrospective cohort study included 207,012 participants without RA at recruitment and completed 24-h dietary recalls. UPF was defined based on the NOVA food classification system. Incident RA was ascertained using the International Classification of Diseases version 10. Cox regression models were used to examine the association between UPF consumption and the incidence of RA. Additionally, mediation analyses were conducted to evaluate the contribution of biomarkers related to the lipid profile, systemic inflammatory factors, serum liver enzymes, and glucose metabolism to the observed associations. Results: The participants' mean (standard deviation [SD]) age at recruitment was 56.08 (7.95) y. During a median follow-up of 12.24 (interquartile range: 11.66-13.03) y, 1869 RA events were recorded. Compared with the lowest quintile of UPF consumption (weight percentage of the UPF), the adjusted hazard ratio (HR) of RA in the highest quintile was 1.17 (95% confidence interval (CI): 1.01, 1.36). There was a 6% elevated risk of RA incidence per SD increase in UPF intake (HR: 1.06; 95% CI: 1.01, 1.11). In the mediation analyses, the biomarkers explained 3.07%-14.80% of the association between UPF intake and RA. Conclusions: Higher UPF consumption was associated with an increased risk of RA, which may be mediated by inflammation, lipids, and liver enzymes. Lower UPF consumption is recommended to reduce RA incidence.