Obesity is common in chronic kidney disease and associates with greater antihypertensive usage and proteinuria: evidence from a cross-sectional study in a tertiary nephrology centre

Abstract

Obesity is a treatable risk factor for chronic kidney disease progression. We audited the reporting of body-mass index in nephrology outpatient clinics to establish the characteristics of individuals with obesity in nephrology practice. Body-mass index, clinical information and biochemical measures were recorded for patients attending clinics between 3^rd August, 2018 and 18^th January, 2019. Inferential statistics and Pearson correlations were used to investigate relationships between body-mass index, type 2 diabetes, hypertension and proteinuria. Mean ± SD BMI was 28.6 ± 5.8 kg/m² (n = 374). Overweight and obesity class 1 were more common in males (P = .02). Amongst n = 123 individuals with obesity and chronic kidney disease, mean ± SD age, n (%) female and median[IQR] eGFR were 64.1 ± 14.2 years, 52 (42.3%) and 29.0[20.5] mL/min/BSA, respectively. A positive correlation between increasing body-mass index and proteinuria was observed in such patients (r = 0.21, P = .03), which was stronger in males and those with CKD stages 4 and 5. Mean body-mass index was 2.3 kg/m² higher in those treated with 4-5 versus 0-1 antihypertensives (P = .03). Amongst n = 59 patients with obesity, chronic kidney disease and type 2 diabetes, 2 (3.5%) and 0 (0%) were prescribed a GLP-1 receptor analogue and SGLT2-inhibitor, respectively. Our data provides a strong rationale not only for measuring body-mass index but also for acting on the information in nephrology practice, although prospective studies are required to guide treatment decisions in people with obesity and chronic kidney disease.

Keywords: chronic kidney disease; diabetes mellitus; diabetic kidney disease; obesity; overweight.

FIGURE 1

BMI distribution of people attending outpatient nephrology clinics, stratified by gender. Panel A: Histograms of BMI distribution stratified by gender. Black vertical dashed lines on the x‐axis (BMI) demarcate cutoffs for defining WHO BMI categories at 18.5, 25, 30, 35 and 40 kg/m². Panel B: Frequency of WHO BMI categories by gender. Definition of WHO BMI categories is as follows: underweight (<18.5 kg/m²), normal weight (18.5‐24.9 kg/m²), overweight (25‐29.9 kg/m²), obesity class 1 (30‐34.9 kg/m²), obesity class 2 (35‐39.9 kg/m²), and obesity class 3 (≥40 kg/m²). Females are shaded in red, males in blue

FIGURE 2

Cross‐sectional relationships between BMI, urine protein‐to‐creatinine ratio (uPCR) and glycated haemoglobin amongst people with obesity and CKD. Panel A: Scatterplot of BMI and uPCR reveals a modest positive correlation (r = 0.21, P = .03). Panel B: Scatterplot of BMI and uPCR stratified by gender. Panel C: Scatterplot of BMI and uPCR stratified by CKD stage. G3 = grade 3 (eGFR 30‐60 mL/min/BSA); G4/5 = grades 4 and 5 (eGFR <30 mL/min/BSA). Panel D: Scatterplot of BMI and uPCR stratified by type 2 diabetes mellitus status. Individuals with type 1 diabetes mellitus were removed from the non‐type 2 diabetes mellitus group in this plot. Panel E: Scatterplot of BMI and HbA_1c reveals no relationship between the two variables (r = 0.003, P = .97). Panel F: Scatterplot of BMI and HbA_1c stratified by type 2 diabetes mellitus status. Individuals with type 1 diabetes mellitus were removed from the non‐type 2 diabetes mellitus group in this plot. Reported r and P values are derived from Pearson correlations. P <.05 was considered statistically significant

FIGURE 3

Cross‐sectional relationships between BMI and antihypertensive usage amongst people with obesity and CKD. Panel A: Boxplots of BMI stratified by the number of antihypertensive medications. Comparisons between three groups are made by ANOVA; comparisons between two groups by independent samples t test. Panel B: Boxplots of eGFR stratified by the number of antihypertensive medications. Comparisons between three groups are made by the Kruskal‐Wallis test; comparisons between two groups by Wilcoxon rank‐sum test. Panel C: Boxplots of uPCR stratified by the number of antihypertensive medications. Comparisons between three groups are made by the Kruskal‐Wallis test; comparisons between two groups by Wilcoxon rank‐sum test. The number of antihypertensive medications was categorized into three groups as follows: 0 to 1, 2 to 3 and 4 to 5. The size of individual data points is scaled by BMI, emphasizing the cross‐sectional associations between increasing BMI with increasing uPCR and antihypertensive usage. P <.05 was considered statistically significant