Bariatric Surgery and the Incidence of Rheumatoid Arthritis

A Swedish Obese Subjects Study

Cristina Maglio; Yuan Zhang; Markku Peltonen; Johanna Andersson-Assarsson; Per-Arne Svensson; Christian Herder; Anna Rudin; Lena Carlsson


Rheumatology. 2020;59(2):303-309. 

In This Article

Abstract and Introduction


Objective: The aim of this study was to determine the effect of bariatric surgery on the incidence of RA in participants of the Swedish Obese Subjects (SOS) study.

Methods: The SOS is a longitudinal study aiming to assess the effect of bariatric surgery on mortality and obesity-related diseases. This report includes 2002 subjects with obesity who underwent bariatric surgery and 2034 matched controls; none of them had RA at baseline. Cases of incident RA were identified through the Swedish National Patient Register by searching for International Classification of Diseases codes. Both intention-to-treat analyses and per-protocol analyses are reported. In the per-protocol analysis, participants from the control group who underwent bariatric surgery later on during follow-up were censored at the time of surgery.

Results: During follow-up, 92 study participants developed RA. The median follow-up was 21 years (range 0–29). Bariatric surgery was neither associated with the incidence of RA in the intention-to-treat analysis [hazard ratio (HR) 0.92 (95% CI 0.59, 1.46), P = 0.74], nor in the per-protocol analysis [HR 0.86 (95% CI 0.54, 1.38), P = 0.53]. Weight change at the 2 year follow-up, expressed as the change in BMI compared with baseline, did not associate with the development of RA. Higher serum CRP levels and smoking associated with the future development of RA independent of other factors.

Conclusions: We did not detect any association between bariatric surgery and the incidence of RA in subjects affected by obesity followed up for up to 29 years.


RA is a chronic inflammatory autoimmune disease affecting primarily the joints. The disease is characterized by the breakdown of self-tolerance mechanisms in genetically susceptible individuals and by the activation of both innate and adaptive immunity, leading to autoantibody formation (RF and ACPA), synovial inflammation and cartilage and bone damage. The pathogenesis of RA is complex and far from fully understood.[1] Several factors have been identified that represent a risk for the development of RA, including female sex, genetic predisposition and smoking.[2] Large meta-analyses have also shown that obesity is among the risk factors for the development of RA, especially among women.[3–6] Moreover, in subjects with RA, obesity is associated with higher disease activity and lower chance to achieve sustained remission.[7–10] Subjects with obesity and RA also have a worse response to therapy, including treatment with biologic DMARDs.[11–13]

Bariatric surgery–induced weight loss in subjects with RA has been associated with lower disease activity, a decrease in inflammatory markers and a decreased use of DMARDs.[14] However, it is not known if bariatric surgery is able to prevent the development of RA in individuals with obesity.

The Swedish Obese Subjects (SOS) study is a longitudinal controlled study on the effect of bariatric surgery on mortality and on the incidence of obesity-related diseases.[15,16] We have recently shown that, in individuals with obesity, bariatric surgery associates with a lower risk of developing gout and psoriasis, two common inflammatory diseases.[17,18] The aim of this study was to determine whether bariatric surgery associated with a lower incidence of RA in SOS study participants.