Predictors of longterm changes in body mass index in rheumatoid arthritis.

Objective: Low body mass index (BMI) is a risk factor for poor longterm outcomes in rheumatoid arthritis (RA). The purpose of this study was to identify factors associated with longterm changes in BMI.
Methods: Subjects with RA from the Veterans Affairs (VA) Rheumatoid Arthritis (VARA) Registry (n = 1474) were studied. Information on inflammatory markers, presence of erosions, and smoking status were extracted from the VARA database. BMI was extracted from VA electronic medical records within 14 days of each visit date. VA pharmacy records were queried to identify prescriptions for specific RA therapies within 1 month of the visit date. We used robust generalized estimating equations marginal regression models to calculate independent associations between clinical variables and BMI over time. Similar models determined predictors of change in weight and risk of weight loss over the subsequent study observation period.
Results: Increasing age, active smoking, and the presence of erosions at baseline were associated with lower BMI. Weight decreased over time among older adults. Factors associated with greater reductions in BMI over time and a greater risk of weight loss were higher inflammatory markers, smoking, older age, higher BMI, and less subsequent improvement in inflammation. Methotrexate use was associated with a lower risk of weight loss. The use of prednisone or anti-tumor necrosis factor therapies was not associated with change in BMI or the risk of weight loss independent of other factors.
Conclusion: Greater age, greater inflammatory activity, and active smoking are associated with greater weight loss in RA over time.