A protective effect of high levels of tea consumption on the development of rheumatoid arthritis (RA) in smokers and anti-citrullinated protein antibody (ACPA)-positive RA was seen in a Swedish study published in Arthritis Research and Therapy.
In this population-based case-control study, researchers compared tea consumption in 2237 patients with RA diagnosed from 2005 to 2018 vs 4661 control participants matched on age, sex, and residential area at the time of the index patient’s diagnosis. Tea consumption was assessed using a questionnaire and categorized as none (0 cups/day), irregular (less than 1 cup/day), regular (1 to 2 cups per day), and high (2 or more cups per day). Irregular consumption was the reference category.
Patients and control participants were similar in their tea consumption. There was an inverse association between high tea consumption and the risk for RA (OR = 0.78; 95% CI, 0.66-0.92.), however the association was not statistically significant after adjusting for education, BMI, smoking, alcohol intake, and coffee consumption (adjusted OR = 0.85; 95% CI, 0.71-1.01). In patients with ACPA-positive RA and among current smokers, there was a significant protective effect of high tea consumption (adjusted OR = 0.76; 95% CI, 0.62-0.94 and adjusted OR = 0.60; 95% CI, 0.38-0.95, respectively).
Limitations of the study included missing tea consumption data (especially for those who were assumed to be no-tea consumers) and the potential for recall bias due to self-reporting.
The researchers concluded, “This study showed an inverse association with the risk of RA among high tea consumers compared to irregular consumers among smokers and in the ACPA-positive subset of RA. We could not draw any conclusion about no tea consumption and the risk of RA, due to the possibility of bias.”
Westerlind H, Palmqvist I, Saevarsdottir S, Alfredsson L, Klareskog L, Di Giuseppe D. Is tea consumption associated with reduction of risk of rheumatoid arthritis? A Swedish case-control study. Arthritis Research & Therapy. Published online August 7, 2021. doi:10.1186/s13075-021-02583-y.