Body Mass Index, Weight Loss, and Cause‐Specific Mortality in Rheumatoid Arthritis

Abstract

Objective. To examine associations of body mass index (BMI) and weight loss with cause-specific mortality in rheumatoid arthritis (RA). Methods. A cohort of US veterans with RA was followed until death or through 2013. BMI was categorized as underweight, normal, overweight, and obese. Weight loss was calculated as the 1) annualized rate of change over the preceding 13 months, and 2) cumulative percent. Vital status and cause of death were obtained from the National Death Index. Multivariable competing-risks regression models were utilized to assess the time-varying associations of BMI and weight loss with cause-specific mortality. Incorporation of time-varying BMI and weight loss in the same models did not substantially alter individual associations for cardiovascular and cancer mortality, but an association between weight-loss percentage and respiratory mortality was attenuated after BMI adjustment. Conclusion. Both BMI and weight loss are predictors of cause-specific mortality in RA. Weight loss is a strong predictor of cardiovascular and cancer mortality, while underweight BMI is a stronger predictor of respiratory mortality.

Weight Change During the Early Rheumatoid Arthritis Period and Risk of Subsequent Mortality in Women With Rheumatoid Arthritis and Matched Comparators

“…It is unclear how generalizable these results might be to other contemporary populations. Overall, our results showing an association between severe weight loss and increased mortality are similar to the results of 2 prior studies investigating weight loss and mortality that were performed among mostly men with RA . We constructed the weight change period around the RA diagnosis as a time point that is relevant to all patients diagnosed with RA and chose the baseline period prior to RA diagnosis to protect against reverse causation with RA symptoms affecting the initial weight in patients with RA.…”

Reply

“…Therefore, we maximized the opportunity to detect a difference between RA patients and non‐RA subjects for weight change and mortality risk. Prior studies used RA‐only cohorts, mostly with longstanding disease, so weight change was not necessarily related to RA and may have immediately preceded death . In our study, we found a similar magnitude of effect for the relative risk of weight change on mortality in both RA patients and comparators, so we believe the obesity paradox occurs similarly in these populations.…”

Increased cardiovascular risk in rheumatoid arthritis: mechanisms and implications

“…Although obesity is a recognized cardiovascular risk factor, an “obesity paradox” has been observed in rheumatoid arthritis whereby greater body mass is protective of cardiovascular disease mortality 85. Proposed hypotheses include the inadequacy of commonly used body composition measures, epidemiologic phenomena such as index event bias,86 confounding by comorbidity,85 and lack of consideration of weight trajectories 8788. Adiposity itself may contribute to systemic inflammation, insulin resistance, and cardiovascular disease risk through the release of adipokines or other pro-inflammatory mediators 8990919293…”