Body mass index and persistence of conventional DMARDs and TNF inhibitors in rheumatoid arthritis

OBJECTIVES: Obese patients with rheumatoid arthritis (RA) may be more likely to discontinue therapy than non-obese patients, possibly signifying a more refractory phenotype. The purpose of this study was to examine the association between body mass index (BMI) and discontinuation rates for different RA treatments accounting for confounding factors. METHODS: Veterans Affairs administrative databases were used to define initial courses of methotrexate (MTX), hydroxychloroquine, sulfasalazine, prednisone, and self-injectable tumour necrosis factor inhibitors (TNFi). Discontinuation was defined as a lapse in drug refill >90 days. Using overweight BMI (25-30 kg/m2) as the referent group, multivariable Cox proportional hazards models were used to evaluate associations between BMI category and time to treatment discontinuation. RESULTS: There were 46,970 initial RA treatment courses identified from 2005-2014 among 23,669 Veterans with RA. In multivariable models, severe obesity (BMI >35 kg/m2), compared to overweight BMI, was not associated with treatment discontinuation with the exception of prednisone [HR 1.10 (1.04, 1.17) p<0.001]. Patients with low (<20 kg/m2) and normal BMI (20-25 kg/m2) were more likely to discontinue MTX, TNFi, and HCQ compared to overweight patients. Other factors associated with earlier MTX and/or TNFi discontinuation included female sex, black race, greater comorbidity, depression, malignancy, congestive heart failure, current smoking, and more recent calendar year. CONCLUSIONS: Obesity was not associated with therapy discontinuation among veterans with RA after accounting for confounding factors, suggesting that obesity is not a biological mediator of more refractory disease. Conversely, low BMI, comorbidity, and depression were identified as important predictors of drug discontinuation.