Mediterranean diet and rheumatoid arthritis: A nine-year cohort study and systematic review with meta-analysis.

BACKGROUND: Although the Mediterranean diet (MD) has beneficial effects on heart health, cognitive function, cancer, and other chronic diseases, little is known about its effect on rheumatoid arthritis (RA). This study aimed to examine the association between adherence to MD and the risk of developing rheumatoid arthritis RA. METHODS: We conducted a cohort study and a systematic review. A total of 117,341 RA-free participants from the UK Biobank were included in 2006-2010 and followed for incident RA until 2021. The MEDI-LITE score was calculated using the consumption of nine food components to estimate adherence to MD. We examined the associations between the MEDI-LITE score and the risk of RA using the Cox proportional hazard model. Relevant studies for the systematic review were identified through six databases. We performed a meta-analysis to pool the effect estimates from our cohort study and identified relevant studies. RESULTS: During a median follow-up of 9.42 years, 773 participants developed RA. Compared with the bottom quartile of the MEDI-LITE score, the risk of RA was lower in the highest quartile (adjusted hazard ratio (HR) = 0.713, 95% CI = 0.580 to 0.876). Six studies were included in the meta-analysis. The pooled odds ratio (OR) for the highest versus lowest adherence to MD and the risk of RA was 0.838 (95% CI = 0.758 to 0.926). CONCLUSION: Higher adherence to MD was associated with a lower risk of RA. Our finding provides updated evidence on the importance of diet in RA development and novel directions for RA prevention.