The relationship between rheumatoid arthritis and diabetes mellitus: a systematic review and meta-analysis

Objective This systematic review/meta-analysis was conducted to investigate the relationship between rheumatoid arthritis and the incidence of diabetes mellitus. Methods A comprehensive search was conducted up to 10 March 2020 in Medline (via Ovid), Embase (via Ovid) and Web of Science core collection to identify cohort studies comparing the risk of diabetes mellitus incidence in people with rheumatoid arthritis with the general population. The I2 statistic was used to test heterogeneity. Pooled relative risks were calculated using random-effects models. Publication bias was assessed using Egger's test and Begg's test. Results The initial search provided 3669 articles. Of those, five journal articles/two conference abstracts comprising 1 629 854 participants were included in this study. The funnel plot showed potential publication bias, proven by Egger's test (-3.15, P < 0.01), but not Begg's test (-0.05, P = 1.00). Heterogeneity was observed in I2 test (I2 = 96%, P < 0.01). We found that rheumatoid arthritis was associated with a higher risk of diabetes mellitus incidence (pooled relative risk, 1.23; 95% confidence interval, 1.07-1.40). Exploration of potential sources of heterogeneity found significant heterogeneity in different countries/regions (P = 0.002), but heterogeneity was NS in different study designs (P = 0.30). Sensitivity analyses confirmed that the association between rheumatoid arthritis and diabetes mellitus incidence was robust. Conclusion Rheumatoid arthritis is associated with an increased risk of diabetes mellitus incidence. This finding supports the notion that inflammatory pathways are involved in the pathogenesis of diabetes. More intensive interventions targeting diabetes risk factors should be considered in people with rheumatoid arthritis.