Supplementary Material for: Tea Consumption Is Associated with Decreased Disease Activity of Rheumatoid Arthritis in a Real-World, Large-Scale Study

Introduction: The role of tea consumption on rheumatoid arthritis (RA) has been studied in recent years, but no clear conclusion has been drawn as a result of small sample size of the studies or the fact that only in vitro studies have been performed. Objectives: The aim of this study was to explore the possible association of tea consumption with RA through a large-scale, real-world study. Methods: A total of 733 RA patients were investigated from June to December, 2016. The disease activity of RA was assessed according to disease activity score 28-erythrocyte sedimentation rate. The amount and types of tea consumption were recorded by on-site self-administered questionnaires. Logistic regression models were applied to analyze the correlation between tea consumption and disease activity, adjusting for demographics, clinical and laboratory factors. Results: There was an inverse association between tea consumption and disease activity in RA patients (OR 0.66, 95% CI 0.46–0.94). Compared with non-tea drinkers, a higher-intake of tea (>750 mL/day) was associated with lower disease activity of RA (OR 0.39, 95% CI 0.19–0.79), but not low-intake (≤750 mL/day; OR 0.83, 95% CI 0.42–1.63). A significant dose-response association was found between the amount of tea consumption and disease activity (p for trend <0.01). Further hierarchical regression analysis showed that such inverse associations were mainly present in female patients (p = 0.004), non-smokers (p = 0.01) or elders (≥60 years; p = 0.01). Conclusion: Tea consumption is associated with decreased disease activity of RA, suggesting the potential beneficial effect of tea in the disease.