Relation between body mass index and radiological progression in patients with rheumatoid arthritis.

OBJECTIVE: To determine if there is an influence of body mass index (BMI) on the radiological progression in early and longer duration rheumatoid arthritis (RA).
METHODS: Fifty-four patients with RA were observed in a progressive 2 year followup for radiological progression of joint damage. At the beginning of study, 27 (50%) patients had a duration of complaints less than 6 months, grouped as early RA. BMI at the beginning and end of the study were monitored, together with HLA-DRB1 alleles, initial joint erosions, duration of disease, age, sex, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). Outcome was defined as radiographic damage according to yearly increase of Larsen score.
RESULTS: Increased radiographic joint damage of patients was significantly correlated with lower BMI at the beginning of the study (r = 0.363, p < 0.05), the presence of initial joint erosions (r = 0.341, p < 0.01), ESR (r = 0.315, p < 0.05), and CRP at study entry (r = 0.427, p < 0.01). Patients with an increase of Larsen score > or = 5.8/year were found to have a lower weight at the beginning of their complaints (BMI 24.8 +/- 4.7 vs 27.8 +/- 3.8; p < 0.05) as well as after the time of observation (BMI 24.6 +/- 3.7 vs 27.6 +/- 4.9; p < 0.05). Stepwise logistic regression analysis revealed a BMI < 27 at the beginning of disease (beta = 2.04, p = 0.003, odds ratio = 7.69), the presence of HLA-DR4 shared epitope (beta = 1.76, p = 0.015, OR 5.82), and joint erosions at study entry (beta = 1.56, p = 0.044, OR 4.78) as significant predictors for rapid joint damage.
CONCLUSION: Together with the presence of HLA-DR4 shared epitope and erosive disease at study entry, a low BMI at the beginning of RA was found in association with higher radiographic progression in RA. Accordingly, BMI could be of interest as a sensitive and inflammation-independent predictor for radiological outcome of RA.