The relationship between body mass index and estimated glomerular filtration rate

Abstract

INTRODUCTION: The increasing prevalence of chronic kidney disease (CKD) is a major health problem. The prevalence of obesity has also been rapidly increasing worldwide. Few studies have examined the relationship between excess body weight and CKD risk. Aim: To evaluate the possible contribution of increased body mass index (BMI) to impaired renal function in the general population sample. METHODS: The study involved 500 participants older than 30 years (228 men, 272 women, age 57.58±13.68) who visited their general practitioner in Health Center "Dr Simo Milošević". Blood samples, blood pressure anthropometric measures were performed on each participant. Estimated glomerular filtration rate was calculated using the abbreviated equation from MDRD study ("the Modification of Diet in Renal Disease Study") and CKD was defined as eGFR less than 60 ml/min/1.73m². Statistical analysis was performed using SPSS 19.0 software (IBM, Somers, New York, USA). RESULTS: The mean BMI was 25.09±3.54 kg/m² with 0.6% in underweight (BMI<18.5 kg/m²), 17.6% in lower normal (BMI 18.5 to 21.9 kg/m²), 33.2% in upper normal (BMI 22.0 to 24.9 kg/m²) and 48.6% in overweight or obese (BMI>25.0 kg/m²) body mass category. The mean eGFR was 100.33±30.78 ml/min/1.73m² with 112±8.62 in underweight, 116.94±3.8 in lower normal, 102.37±2.39 in upper normal and 92.78±1.72 in overweight or obese category. Estimated GFR values decreased significantly with increasing BMI specially in those in upper normal compared to lower normal (p<0.001) and overweight and obese compared to lower normal body mass category (p<0.001). Compared with participants with lower normal body mass, the non-adjusted odds ratio (OR) for mildly or moderately reduced renal function (eGFR<90 ml/min/1.73m²) was 2.54 (95% CI 1.41-4.56) for upper normal and 3.26 (95% CI 1.88-5.70) for overweight and obese participants. After adjusting for potential confounding variables (age, sex, diabetes mellitus, hypertension, hypercholesterolemia, hypertriglyceridemia and smoking status) or for mildly or moderately reduced renal function was 2.23 (95% CI 1.21-4.10) for upper normal 2.65 (95% CI 1.44-4.87) for overweight or obese participants compared to those in lower normal body mass category. CONCLUSION: Estimated GFR values decreased significantly with increasing BMI specially in those in upper normal compared to lower normal (p<0.001) and overweight and obese compared to lower normal body mass category (p<0.001). This study showed that increasing BMI is strongly associated with decreasing eGFR in the general population. The underlying mechanism behind this association remains to be investigated through prospective population-based studies.