The evidence from published studies on the association between obesity and rheumatoid arthritis (RA) has been contradictory. To clarify the association between obesity and RA, we conducted a systematic review and dose-response meta-analysis to assess the relationship between body mass index (BMI) and RA risk.
A systematic literature search of Pubmed and Embase (up to July 12, 2014) was performed to identify all eligible published reports. The pooled relative risk (RR) results with corresponding 95% confidence intervals (CIs) of RA development were estimated using a random effects model.
Eleven eligible related citations fulfilled the inclusion criteria and were included in the study. Compared with individuals with BMI < 30, obese individuals showed an association with a significantly increased risk of RA (RR = 1.25, 95%CI 1.07-1.45, Pheterogeneity < 0.01, I(2) = 63%). Compared to normal weight subjects, the pooled RRs for RA were 1.31 (1.12-1.53) and 1.15 (1.03-1.29) for the categories of obese and overweight, respectively. In the dose-response analysis, there was evidence of a nonlinear association (Pnon-linear =0.005) and the estimated summary RR for a 5-unit increment was 1.03 (95%CI 1.01-1.05, Pheterogeneity = 0.001, I(2) = 70.0%).
An increase in BMI can contribute to a higher risk for RA development. However, the finding also highlights the need for research on the association between BMI and RA risk with adjustment for more confounding factors.