Diabetic nephropathy in non-insulin-dependent diabetes mellitus: Natural history and risk factors.

Abstract

We reviewed medical records of 704 patients with noninsulin dependent diabetes mellitus (NIDDM), who were admitted to the University of Michigan Hospital between 1978 and 1987. Data were analysed for 517 patients for whom complete information was available. Diabetic nephropathy was defined by persistent proteinuria ($>$0.50 g/24 hours). The cumulative incidence of nephropathy was estimated, using the Kaplan-Meier survival analysis method. Incidence rates increased with duration of diabetes (1.1%; 5.2%; 10.7%; 32.7%; and 45.0%) for durations of 5, 10, 15, 20 and 25 years respectively. We conclude from the descriptive part of the study that the risk of nephropathy in NIDDM increases with age and duration of diabetes and is similar to that observed in populations with IDDM. To assess the role of risk factors in determining the risk for nephropathy in NIDDM, we performed a case-control study in 189 subjects. Comparisons were made between 80 cases with diabetic nephropathy, 72 controls with normal urine protein levels ($<$0.15 g/24 hours) and a small group of 37 patients with microproteinuria (0.15-0.50 g/24 hours). Data were collected by medical chart abstracting, and by written questionnaires. Using logistic regression models, the risk for nephropathy was found to be associated with duration of diabetes of 15 years or more (O.R. $\approx$ 10.0; 95% C.I. = 2.64, 40.8) and with poor glycemic control, measured by levels of glycosylated hemoglobin above 8.5%(O.R. = 2.8; C.I. = 1.16, 7.08). A significantly higher proportion of patients with nephropathy had an average systolic blood pressure above 140 mmHg compared to controls (O.R. = 2.9; C.I. = 1.21, 6.94). Nephropathy was also found to be significantly associated with above normal levels of triglycerides ($\geq$170 mg/dl) (O.R. = 3.1; C.I. = 1.10, 8.52) and with a positive history of diabetic foot syndrome (O.R. = 4.7; C.I. = 1.42, 15.73). We concluded that duration of diabetes, poor glycemic control and poorly controlled blood pressure are important predictors for the risk of developing nephropathy in NIDDM.