Effect of age on the development or progression of albuminuria in non-insulin-dependent diabetes mellitus (NIDDM) without hypertension.

To study the relationship between aging and development of diabetic nephropathy, we studied the time until the development of microalbuminuria in old onset (> 50 years old, n = 21) and young onset (< 40 years old, n = 26), normotensive NIDDM patients. Microalbuminuria which is associated with the early stage of diabetic nephropathy was defined as urinary albumin index (UAI; mg/g.creatinine) of more than 10mg/g.creatinine, using timed overnight urine. In these two groups, there were no significant differences in duration of diabetes, observation periods, glycemic control, systolic diastolic blood pressure, body mass index and creatinine clearance at the time of the last observation. Mean UAI +/- standard deviation of the two groups were 37.5 +/- 78.2 mg/g.cr and 93.0 +/- 127.2 mg/g.cr in the young onset group and the old onset group, and prevalences of microalbuminuria were 38% and 76% in the young onset and old onset group, respectively. Thus, UAI and prevalence of microalbuminuria in the old onset group are significantly higher than those of the young onset group (P < 0.05). These results suggest that aging, in itself, is one of the significant risk factors for the development of diabetic nephropathy in NIDDM patients.