Because early-onset Japanese NIDDM patients (diagnosed before age 30 years) can develop diabetic end-stage renal failure (ESRF) in their thirties, this study was performed to elucidate the incidence and determinants for the development of diabetic nephropathy.
The incidence of diabetic nephropathy and its relationship to baseline characteristics and long-term metabolic control were determined in 426 early-onset Japanese NIDDM patients who were followed for a mean of 6.8 years.
Of these 426 patients, 41 developed diabetic nephropathy manifested by persistent proteinuria (incidence rate [95%CI]/1,000 person-years; 14.1 [10.4–19.1]). Among patients whose mean HbA1c (measured by a high-performance chromatography method that is standardized and comparable to the one used in the Diabetes Control and Complications Trial study) was around 7% or less, few developed nephropathy. The incidence of nephropathy increased with increasing mean HbA1c level in a dose-dependent manner (χ2 trend = 49.9, P < 0.0001). Diastolic blood pressure and duration of diabetes at entry had significant predictive effects independent of metabolic control.
The incidence rate of diabetic nephropathy in early-onset Japanese NIDDM patients is potentially high, similar to or higher than that in Pima Indian NIDDM or Caucasian IDDM patients of comparable age. Diabetic nephropathy in NIDDM patients aged in their thirties or forties is likely to be an early feature that leads to ESRF, and this would contribute to the marked increase in the number of new patients with diabetic ESRF in Japan. NIDDM is a serious disease if near-normal glycemia is not achieved.