Correlation between body mass index and disease activity in patients with systemic lupus erythematosus from China

Objective To assess the association between clinical indicators (primarily Body Mass Index, BMI) and disease activity in systemic lupus erythematosus (SLE) populations in a large population-based cohort. Methods Four hundred consecutive patients with SLE were studied to determine the relation among clinical features, inflammatory and biochemical indicators, and parameters of disease activity. Significance values have been adjusted by Bonferroni correction for multiple tests, then differences between continuous variables were analysed by Kruskal Wallis tests. Multivariate analyses were carried out by multiple linear regression models. Results Four hundred SLE patients were included in the study, including 375 women and 25 men. 61 patients (15.25%) were underweight (BMI<18.5 kg/m²), 267 patients (66.75%) had a normal BMI (18.5 kg/m²≤BMI<25 kg/m²), and 72 (18.00%) were overweight (BMI ≥ 25kg/m²). BMI was negatively correlated with SLE disease activity index (SLEDAI) score (ρ=-0.11, P = 0.02) and positively correlated with inflammatory index complement component 3 (C3, ρ = 0.19, P = 1.16x10^-4). Patients in underweight group had the highest proportion (14.8%) of moderate to severe disease activity (SLEDAI ≥ 10) compared to normal weight (3.4%) and overweight (1.4%) patients. SLEDAI score, Anti-dsDNA, C3, WBC count, ALT, NEUT and HGB were significantly different between the underweight group and the other two groups. Conclusions These findings suggest that SLE patients with low BMI have higher disease activity, which means low BMI exerted a negative impact on disease activity in SLE patients. Causal relation between disease activity and BMI requires further investigation.