Various factors affect joint damage in rheumatoid arthritis (RA). The influence of body mass index (BMI) is not adequately known. As BMI is potentially modifiable, we studied its influence on radiological joint damage in patients with RA.
Treatment-naive patients with early RA (< 24 mo) were included. Demographic data were collected along with swollen joint count (SJC), tender joint count (TJC), erythrocyte sedimentation rate (ESR), and IgM-rheumatoid factor (IgM-RF). Radiographs of hands and feet were obtained. BMI and Disease Activity Score for 28-joint count (DAS28-ESR) were calculated. Joint damage was assessed using the Simplified Erosions Narrowing Score (SENS).
A total of 101 patients were studied (81 women; mean age 41.91 ± 11.99 yrs). Mean disease duration was 10.77 ± 6.73 months; 55 patients (54.5%) were IgM-RF-positive. Mean BMI was 22.82 ± 4.66 kg/m(2) with 24 (23.8%) patients having low, 42 (41.6%) normal, and 35 (34.7%) high BMI. Mean SENS score was 16.81 ± 11.10; mean DAS28 was 6.23 ± 0.96. Significant correlation was noted between SENS and DAS28 (r = 0.28; p < 0.005). There was significant negative correlation between BMI and SENS (r = -0.509; p < 0.0005). In patients with low BMI, mean SENS (26.62 ± 13.45) was significantly higher than in patients with normal (15.88 ± 8.38; p < 0.001) and high BMI (11.20 ± 7.32; p < 0.001). Patients with normal BMI also had significantly higher SENS scores than those with high BMI (p < 0.05). One-way ANOVA did not reveal significant differences in DAS28 between groups. SENS was significantly higher in the IgM-RF-positive group (19.55 ± 11.36) than in the IgM-RF-negative group (13.54 ± 9.94; p < 0.01); DAS28 was not different between the 2 groups (6.22 ± 0.98 vs 6.26 ± 0.96, respectively). Within the 2 IgM-RF groups, a significant negative correlation was seen between BMI and SENS. Multiple regression analysis revealed RF, DAS28, and BMI were independently associated with SENS. BMI accounted for 23.04% of the variance in SENS independent of DAS28 and IgM-RF.
Low BMI is adversely associated with joint damage in patients with early RA.