Albuminuria Within the "Normal" Range and Risk of Cardiovascular Disease and Death in American Indians: The Strong Heart Study

Background: "Normal" albuminuria has been defined as urinary albumin-creatinine ratio (UACR) less than 30 mg/g (3.4 mg/mmol). Whether higher UACR within this range independently predicts cardiovascular disease (CVD) and CVD death is uncertain. Methods: A total of 3,000 participants aged 45 to 74 years with a UACR less than 30 mg/g and free of CVD at the baseline examination of the Strong Heart Study (SHS) were evaluated. Survival time was calculated from the baseline examination to the first nonfatal CVD, fatal CVD, or December 31, 2002. Results: During follow-up (average, 10.4 years), 383 incident nonfatal CVD and 145 fatal CVD cases were ascertained. After adjustment for conventional CVD risk factors, participants with a UACR in the third (UACR ≥ 5.4 to <10.2 mg/g [≥0.6 to <1.1 mg/mmol] in men, ≥7.6 to <12.9 mg/g [≥0.9 to <1.4 mg/mmol] in women) and the fourth (UACR ≥10.2 to <30 mg/g in men, ≥12.9 to <30 mg/g in women) quartiles had 41% and 72% greater risks of all CVD events and 118% and 199% greater risks of CVD mortality than those in the lowest quartile (UACR < 2.7 mg/g [<0.3 mg/mmol] in men, <4.3 mg/g [<0.5 mg/mmol] in women), respectively. In subgroup analysis, these associations were more pronounced in persons with diabetes. Conclusion: In the SHS cohort of middle-aged to elderly American Indians, albuminuria levels less than the traditional cutoff value predict CVD. Our findings agree with a growing number of studies questioning the concept that UACR less than 30 mg/g is normal.