Figure 3: Results of a traditional multivariable model compared to instrumental variable (IV) analysis.

Unadjusted hazard ratios (HR) are from univariate cause-specifics hazards models (unadjusted hazard ratio). Adjusted hazard ratios are from multivariable cause-specific hazards models including all covariates of interest. HR_IV are from instrumental variable analyses (IV) performed using Cox models. IV analyses included covariates with SMD > 0.026 (race, urban versus rural, region, dual Medicare/Medicaid eligibility, median household income quintiles, sulfasalazine, methotrexate, current disease-modifying drug use, number of previous biologics, chronic pain, asthma, number of outpatient visits and number of rheumatology visits in the past year), along with age, age², sex, and covariates strongly associated with the outcome (emergency department visits, prior infection requiring hospitalization).