Natural History and Predictors of Faster Glomerular Filtration Rate Decline in a Referred Population of Older Patients with Type 2 Diabetes Mellitus

Abstract

Aim: To study the natural history and predictors of faster glomerular filtration rate (GFR) decline in a referred population of older patients (aged ≥ 65 years) with type 2 diabetes mellitus. Methods: A retrospective medical record analysis in an outpatient diabetes clinic for older patients. Baseline characteristics and blood pressure readings for each clinic visit were recorded. All laboratory results were downloaded from the central database of the pathology laboratory. Annual rate of GFR decline was calculated by linear regression analysis as the slope per year for each individual. Patients were then divided into 2 groups on either side of the mean GFR decline. Group 1 had a slower GFR decline (below the mean value) and group 2 had a faster GFR decline (above the mean value). Five variables were investigated as predictors of faster decline in GFR: cardiovascular disease (CVD), hypertension, diabetes control, use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, and albuminuria. Results: The study included 100 patients with a mean age of 69.5 (standard deviation [SD], 3.9) years on referral, and 54 patients were men. The mean duration of study was 14.4 (SD, 2.0) years. A total of 3908 GFR results were downloaded during the study. The mean annual rate of GFR decline was 1.5 (SD, 1.2) mL/min/1.73 m2. Glomerular filtration rate values were comparable in both groups on first referral. Mean annual rate of GFR decline was 2.6 (SD, 0.9) mL/min/1.73 m2 in group 2 compared with 0.7 (SD, 0.5) mL/min/1.73 m2 (P < 0.001) in group 1. Development of CVD was the only independent predictor of faster renal function decline (odds ratio, 2.9; 95% CI, 1.1−7.6; P = 0.03). Conclusion: Cardiovascular disease is an independent risk factor for faster decline in GFR in older patients with type 2 diabetes mellitus.