The body mass index: a determinant of remission in early rheumatoid arthritis

Background: There are evidences that obesity determines higher disease activity status in rheumatoid arthritis (RA) and that obesity possibly affects the response to therapy in long standing RA. There are only few data about early RA (ERA), showing that obesity associates with a less erosive disease, with no clear explanation.
Objectives: To evaluate whether the body weight could influence the outcomes in patients with ERA in terms of disease remission and treatment after 6 and 12 month of follow-up.
Methods: 346 patients with ERA (symptoms duration <12 months), treated according to a treat-to-target strategy aiming at remission (strict follow-up visits, treatment with methotrexate up to 25 mg/week±steroids; then a combination with a TNF blocker if at least a good response according to EULAR criteria was not obtained), were enrolled. At each visit the ACR/EULAR core data set was registered. Baseline BMI was collected. Clinical remission was evaluated according to DAS and CDAI (Clinical Disease Activity Index) values. The BMI was categorized into three classes, as a BMI <25 Kg/m2 (normal weight), 25-30 (overweight) and >30 (obese), according to the NIH classification. Logistic regression models were applied to determine the influence of the independent variables that reached the value of p<0.25 at the univariate analysis, on the dependent variables “DAS and CDAI remission at 12th month and anti-TNF therapy at 12th month”.
Results: Of the 346 ERA patients (76.3% female, age 54.6±14.0 years, 32.9% very ERA, 70.2% seropositive, baseline DAS 3.6±1.1), 168 (48.6%) were normal weight, 135 (39%) overweight and 43 (12.4%) obese. The BMI values correlated with age (r=0.23, p<0.001), baseline inflammatory markers (ESR: r=0.14, p=0.009, CRP: r=0.19, p<0.001), DAS (r=0.18, p=0.001), CDAI (r=0.14, p=0.01), HAQ (r=0.17, p=0.001). Overweight and obese patients reached a lower rate of remission, both with DAS and CDAI criteria, at 6 and 12 month follow-up visits (sustained DAS remission at 12th month: 49.1% in normal, 28.7% in overweight, 34.1% in obese, p=0.008; CDAI remission at 12th month: 50%, 37.1%, 31% in normal, overweight and obese, respectively, p=0.07). Moreover, an higher percentage of obese and overweight ERA patients were under anti-TNF treatment after 12 months of follow-up (28.1% of obese, 28.8% of overweight, 16.2% of normal weight). At the multivariate analysis, the independent baseline variables associated with the risk of “not obtaining a sustained DAS remission at 12th month follow-up” were female gender (OR (95% CI): 2.44 (1.56-21.45)), baseline HAQ≥1.5 (OR: 1.56 (1.47-5.94)) and a BMI≥25 (OR: 2.22 (1.13-4.1)), whereas the variables identifying the “non-CDAI remission at 12th month” were female sex (OR: 1.97 (1.04-3.73)), baseline HAQ≥1.5 (OR: 1.76 (1.0-3.15)) and a BMI≥25 (OR: 1.81 (1.04-3.13)). The independent variables associated with the probability of being in anti-TNF therapy at 12th month follow-up were an age <55 years (OR: 2.7 (1.4-5.3)), baseline DAS≥3.7 (OR: 2.27 (1.19-4.34) and BMI≥25 (OR: 2.36 (1.21-4.59)).
Conclusions: Data suggest that in ERA patients, not only obesity but also overweight, associates with a lower percentage of success in obtaining remission. Overweight ERA subjects required 2.4 times more anti-TNF therapy, than normal weight to achieve the outcomes. BMI is one of the few modifiable variables influencing the major outcomes in RA.