Obesity Associated With Renal Function Decline, Kidney Disease Risk

Se Won Oh, MD, PhD

Credit: Korea University

Findings from a recent study are providing clinicians with an overview of the impact of obesity on the prevalence and progression of glomerular diseases, highlighting an increased risk of focal segmental glomerulosclerosis and hypertensive nephropathy in patients with body mass index (BMI) ≥ 30 kg per m².¹

An analysis of patient data for nearly 15,000 kidney biopsies in Korea showed being classified as obese was associated with a greater risk of several prominent kidney diseases, also increasing the risk of end-stage kidney disease (ESKD) in patients with accompanying renal diseases such as immunoglobulin A nephropathy (IgAN) and lupus nephritis.¹

The connection between obesity and kidney disease is multifaceted, with obesity being recognized as a significant risk factor for the development and progression of various kidney disorders. Despite obesity’s known exacerbation of kidney disease, clinicians’ understanding of how this impacts the overall prevalence and worsens outcomes in this patient population is limited.²

“Obesity causes kidney injury by various mechanisms,” Se Won Oh, MD, PhD, of the division of nephrology in the department of internal medicine at Korea University Anam Hospital, and colleagues wrote.¹ “However, the association of obesity with various immune complex-mediated glomerulonephritis is not well known.”

To determine how obesity may impact the prevalence and progression of glomerular diseases, investigators retrospectively examined electronic medical record data and kidney biopsy results for patients from 18 hospitals across Korea from 1979 - 2018. After excluding patients < 18 years of age and those who had tumors such as renal cell carcinoma, transplantation, and donor or inadequate samples, a total of 14,492 participants were enrolled in the study.¹

Among the cohort, 969 patients had BMI ≥ 30 kg per m2 and were thus classified as having obesity. Most (57%) patients with obesity were male and were slightly younger (mean age, 42.6 years) than non-obese patients (mean age, 43.2 years).¹

Investigators noted patients with obesity had significantly greater systolic blood pressure, diastolic blood pressure, hemoglobin, glucose, cholesterol, and uric acid levels (all P <.001). An increased prevalence of diabetes mellitus and hypertension was observed in obese participants compared to those without obesity, while that of cancer was significantly lower in patients with obesity versus those without (all P <.001).¹

IgAN was the most common disease observed across both obese and non-obese groups (33.7% vs. 38.9%). Upon analysis, obesity was associated with a greater risk of focal segmental glomerulosclerosis (odds ratio [OR], 1.72; 95% CI, 1.37–2.17) and hypertensive nephropathy (OR, 1.96; 95% CI, 1.21–3.19) but a lower risk of IgAN (OR, 0.74; 95% CI, 0.62–0.88).¹

During a median follow-up of 93.1 months, 1842 patients developed ESKD. Investigators pointed out obesity increased the risk of ESKD in patients with IgAN (relative risk [RR], 1.49; 95% CI, 1.01–2.20) and lupus nephritis (RR, 3.43; 95% CI, 1.36–8.67).¹

Of 947 patients with obesity, obesity-related glomerulopathy was detected in 298 (31.5%). Other kidney diseases were observed in 230 of these patients, most commonly IgAN (40.9%) followed by diabetic nephropathy (15.2%), membranous nephropathy (13.5%), minimal change disease (8.3%), and lupus nephritis (3.9%). Of note, patients with obesity-related glomerulopathy and other renal diseases had a greater risk of developing ESKD compared to those with obesity-related glomerulopathy alone (RR, 2.48; 95% CI, 1.09–5.64).¹

Investigators called attention to multiple limitations within their study to consider. These included, but were not limited to, the retrospective study design, limited availability of treatment data, and a lack of BMI results for 31.6% of total kidney biopsies potentially leading to bias in the patient selection.¹

“Given that there have been only few reports on pathologic data in severely obese participants in Asia, our study shows the heterogeneity of kidney pathology and outcomes in obese participants and indicates the importance of a kidney biopsy in both deciding the management and predicting outcomes,” investigators concluded.¹

References:

1. Kim TB, Ahn SY, Oh J, et al. The Impact of Obesity on Kidney Disease: Observational Cohort Study Analyzing 14,492 Kidney Biopsy Cases. J Korean Med Sci. 2023 Dec;39(3):e12. https://doi.org/10.3346/jkms.2024.39.e12
2. American Kidney Fund. Obesity and chronic kidney disease. December 20, 2022. Accessed February 1, 2024. https://www.kidneyfund.org/all-about-kidneys/risk-factors/obesity-and-chronic-kidney-disease