A longitudinal study of risk factors for incident albuminuria in diabetic American Indians: the Strong Heart Study

Abstract

Background: There have been no studies that use longitudinal data with more than 2 measurements and methods of longitudinal data analysis to identify risk factors for incident albuminuria over time more effectively.

Study design: Longitudinal study.

Settings & participants: A subgroup of participants in the Strong Heart Study, a population-based sample of American Indians, in central Arizona, Oklahoma, and North and South Dakota. Participants with diabetes without albuminuria were followed up for a mean of 4 years.

Predictors: Age, sex, study center, high-density lipoprotein and low-density lipoprotein cholesterol levels, triglyceride level, body mass index, systolic blood pressure, use of antihypertensive medication, smoking, hemoglobin A(1c) level, fasting glucose level, type of diabetes therapy, diabetes duration, plasma creatinine level, and urinary albumin-creatinine ratio (UACR).

Outcomes & measurements: Albuminuria was defined as UACR of 30 mg/g or greater. Urine creatinine and albumin were measured by using the picric acid method and a sensitive nephelometric technique, respectively.

Results: Of 750 and 568 participants with diabetes without albuminuria and with normal plasma creatinine levels at the first and second examinations, 246 and 132 developed albuminuria by the second and third examinations, respectively. Incident albuminuria was predicted by baseline UACR, fasting glucose level, systolic blood pressure, plasma creatinine level, study center, current smoking, and use of angiotensin-converting enzyme inhibitors and antidiabetic medications. UACR of 10 to 30 mg/g increased the odds of developing albuminuria 2.7-fold compared with UACR less than 5 mg/g.

Limitations: Single random morning urine specimen.

Conclusions: Many risk factors identified for incident albuminuria can be modified. Control of blood pressure and glucose level, smoking cessation, and use of angiotensin-converting enzyme inhibitors may reduce the incidence of albuminuria.

Figure 1

Participant flow in the Strong Heart Study with development of albuminuria from the 1^st examination to the 2^nd examination and from the 2^nd examination to the 3^rd examination. * UACR: urinary albumin/creatinine ratio. Normal plasma creatinine: ≤1.5 mg/dl for men and 1.3 mg/dl for women. ^† Subgroups: a) the 504 diabetic participants without albuminuria at the 2^nd examination; b) the 67 diabetic participants who had remission of albuminuria at the 2^nd examination; and c) the 294 participants without diabetes or with missing diabetes status at the 1^st examination who developed diabetes by the 2^nd examination. To convert creatinine in mg/dL to µmol/L, multiply by 88.4.