Epidemiology of microalbuminuria in diabetes and in the background population.

Microalbuminuria is defined in principle as abnormally increased albumin excretion below the level that is characteristic for proteinuria. In diabetes, microalbuminuria is defined as having an excretion rate of 20 to 200 micrograms/min. This level of albuminuria predicts overt renal disease in both non-insulin-dependent diabetes mellitus and insulin-dependent diabetes mellitus patients, and it is also associated with increased mortality. In nondiabetic individuals, the albumin excretion rate is not normally distributed with a skewed upper distribution. Excretion rate is lower during daytime, even during rest, than overnight. The median values in several studies for daytime and overnight albumin excretion rates are approximately 4 and 3 micrograms/min, respectively, with the upper 90th percentile approximately 15 and 10 micrograms/min, respectively. Microalbuminuria in population studies is significantly, but weakly, correlated to blood pressure, triglycerides, and low high-density lipoprotein cholesterol, as well as plasma glucose and obesity. These parameters are elements of the so-called metabolic syndrome. New studies in insulin-dependent diabetes mellitus on the transition from normo- to microalbuminuria show that high normal excretion rate and poor metabolic control are associated with progression. In non-insulin-dependent diabetes mellitus, microalbuminuria is quite common (20% to 25% of patients) in both newly diagnosed patients and patients with established diabetes. In many studies, a prevalence of approximately 20% is found, and again microalbuminuria is associated with components of the metabolic syndrome, which includes poor metabolic control and blood pressure elevation.(ABSTRACT TRUNCATED AT 250 WORDS)