Comorbidities As Risk Factors for Rheumatoid Arthritis and Their Accrual After Diagnosis

Objective: To determine the prevalence of comorbidities in rheumatoid arthritis (RA), discover which comorbidities might predispose to developing RA, and identify which comorbidities are more likely to develop after RA. Patients and Methods: We performed a case-control study using a single-center biobank, identifying 821 cases of RA (143 incident RA) between January 1, 2009, and February 28, 2018, defined as 2 diagnosis codes plus a disease-modifying antirheumatic drug. We matched each case to 3 controls based on age and sex. Participants self-reported the presence and onset of 74 comorbidities. Logistic regression models adjusted for race, body mass index, education, smoking, and Charlson comorbidity index. Results: After adjustment for confounders and multiple comparisons, 11 comorbidities were associated with RA, including epilepsy (odds ratio [OR], 2.13; P=.009), obstructive sleep apnea (OR, 1.49; P=.001), and pulmonary fibrosis (OR, 4.63; P<.001), but cancer was not. Inflammatory bowel disease (OR, 3.82; P<.001), type 1 diabetes (OR, 3.07; P=.01), and venous thromboembolism (VTE; OR, 1.80; P<.001) occurred more often before RA diagnosis compared with controls. In contrast, myocardial infarction (OR, 3.09; P<.001) and VTE (OR, 1.84; P<.001) occurred more often after RA diagnosis compared with controls. Analyses restricted to incident RA cases and their matched controls mirrored these results. Conclusion: Inflammatory bowel disease, type 1 diabetes, and VTE might predispose to RA development, whereas cardiovascular disease, VTE, and obstructive sleep apnea can result from RA. These findings have important implications for RA pathogenesis, early detection, and recommended screening.