Risk factors for kidney damage in the adult population of Wadena, Minnesota. A prospective study

An increased albumin excretion rate (AER) is associated with impaired glucose tolerance and diabetes mellitus in some populations, but data on Americans of Northern European origin are lacking. In 1986-1987, AER and creatinine clearance were measured in 455 adults in a survey of the population of Wadena, Minnesota. Thirty-five subjects (8%) had an AER > or = 15 micrograms/minute, and eight of these had overt proteinuria (AER > or = 175 micrograms/minute). AER and creatinine clearance were uncorrelated except when AER was increased. Unadjusted mean AER in a stratified random sample of adults (n = 374) was 3.6 micrograms/minute. Adjusted values for 277 subjects with normal glucose tolerance and for 80 subjects with impaired glucose tolerance were very similar (3.8 and 3.7 micrograms/minute, respectively), whereas mean AER was 5.4 micrograms/minute for persons with non-insulin-dependent diabetes mellitus (NIDDM) who were not taking insulin and 9.4 micrograms/minute for persons with NIDDM who were taking insulin (p < 0.0001). After adjustment for age, mean creatinine clearance was unrelated to glucose tolerance. Systolic blood pressure was a major determinant of increased AER (p < 0.0001) and lowered creatinine clearance (p = 0.0011), independently of diabetes. AER was stable over 5 years among the 321 cases who were not taking insulin and were not severely hypertensive. The decrease in creatinine clearance was greater in ex-smokers and current smokers than in nonsmokers. The authors conclude that hypertension and NIDDM were independently associated with the risk of kidney damage in this population, as indicated by a higher AER. High-normal blood pressure, but not impaired glucose tolerance, was associated with microalbuminuria. These relatively mild changes may reflect an ethnically based resistance to the damaging effects of hyperglycemia on the kidney. Smoking may accelerate the aging-related decline in glomerular filtration rate.