Associations between obesity, weight change and decreased renal function in Korean type 2 diabetic patients: a longitudinal follow-up study

Background We aimed to examine the associations between the risk of decreased renal function, obesity, and weight changes in Korean type 2 diabetic patients with normal renal function. Methods Type 2 diabetic patients (n = 1060) who visited the diabetic clinic at Soonchunhyang University Bucheon Hospital between 2001 and 2007 with follow up surveys completed in 2016 to 2017 were recruited into the study. Decreased renal function was defined as an estimated glomerular filtration rate < 60 mL/min/1.73 m(2). Weight change was calculated between baseline and each follow-up survey. Multivariate analysis was used to evaluate the longitudinal association of baseline obesity and weight changes with the risk of decreased renal function. Results This study revealed that baseline obesity was associated with the risk of decreased renal function after adjusting for clinical variables in type 2 diabetic patients (odds ratio [OR] 1.40; 95% confidence intervals [CI] 1.08-2.04; p = 0.025). Follow-up (mean = 12 years) revealed that weight gain > 10% was associated with the risk of decreased renal function after adjusting for clinical variables in type 2 diabetic patients with normal renal function at baseline (OR 1.43; CI 1.11-2.00; p = 0.016). Weight loss was not associated with the risk of decreased renal function in type 2 diabetic patients with normal renal function at baseline. Conclusions Baseline obesity was associated with the increased risk of decreased renal function in Korean type 2 diabetic patients with normal renal function. Weight gain > 10% independently predicted the risk of decreased renal function. Large prospective studies are needed to clarify causal associations between obesity, weight change, and decreased renal function in patients with type 2 diabetes.