Association of high body mass index with development of interstitial fibrosis in patients with IgA nephropathy

Abstract

Background: The worldwide prevalence of obesity is increasing. Obesity is associated with a variety of chronic diseases, including chronic kidney disease. Several studies suggested that body mass index (BMI) could be an independent risk factor for progression of IgA nephropathy (IgAN). However, whether high BMI is associated with progression of IgAN remains uncertain.

Methods: This retrospective study included patients with biopsy proven IgAN from 2006 to 2017 in Sichuan Provincial People's Hospital. BMI was categorized according to the WHO Asian guideline: underweight (< 18.5 kg/m²), normal weight (18.5-25 kg/m²), overweight (25-28 kg/m²) and obese (≥28 kg/m²). The main outcome was development of end-stage renal disease (ESRD) or a decline in eGFR by at least 30%. The association of BMI and IgAN progression was determined by propensity-score-matched cohort analysis.

Results: Four hundred eighty one patients with IgAN were finally enrolled in this study. The mean age was 37 ± 11 years and 40.3% were men. There was no significant difference in clinical and pathological characteristics among the four-group patients categorized by BMI. After matching with propensity scores, no significant correlation between BMI and renal outcomes was seen. However, compared with the reference group (18.5≦BMI≦25 kg/m²), being overweight (odd ratio [OR], 2.28; 95%CI: 1.06-4.88; P = 0.034) and obese (OR, 3.43; 95%CI: 1.06-11.04; P = 0.039) was associated with a high risk of interstitial fibrosis. In the cross figure demonstrating the association of BMI subgroup and interstitial fibrosis on renal outcomes, ORs of interstitial fibrosis groups were higher than those of no interstitial fibrosis. Compared with other BMI subgroups, patients with 18.5-25 kg/m² had lowest ORs.

Conclusions: High BMI and interstitial fibrosis were associated with progression of IgAN. Interstitial fibrosis appears to be common in IgAN patients with elevated BMI.

Keywords: Body mass index; IgA nephropathy; Interstitial fibrosis; Overweight; Progression; Renal outcomes.

Fig. 1

Study selection flow chart. In this figure, the matched cohort was follow-up matched cohort

Fig. 2

Distribution of BMI in 481 patients with IgAN

Fig. 3

Forest plots of BMI and renal outcomes. Group 1, 2 and 3 all belonged to the follow-up matched cohort. P value of Logistic and KM were analyzed by logistic regression and Kaplan-Meier survival analysis

Fig. 4

Forest plots of BMI and interstitial fibrosis. Group 1, 2 and 3 all belonged to the based matched cohort. The patients with normal weight (18.5 ≤ BMI<25 kg/m²) were set as reference. Finally, 48 underweight patients matched 48 normal weight patients in group 1, 75 overweight patients matched 75 normal weight patients in group 2, and 32 obese patients matched 32 normal weight in group 3. In the Logistic analysis, interstitial fibrosis was defined as the event and the factor was BMI

Fig. 5

The analysis of additive effect of BMI and interstitial fibrosis on renal outcomes. X-axis standed for interstitial fibrosis, Z-axis standed for subgroups of BMI, and the Y-axis standed for the OR value. Patients with interstitial fibrosis and normal weight were set as the reference. The ORs were 1.65 (95%CI: 0.49–5.61; P = 0.42), 1.34 (95%CI: 0.51–3.5; P = 0.55), 0.83 (95%CI: 0.10–7.07; P = 0.86), 0.54 (95%CI: 0.20–1.46; P = 0.23), and 0.78 (95%CI: 0.16–3.71, P = 0.75), respectively