Cystatin C, Albuminuria, and Mortality Among Older Adults With Diabetes

OBJECTIVE: Albuminuria and impaired glomerular filtration rate (GFR) are each associated with poor health outcomes among individuals with diabetes. Joint associations of albuminuria and impaired GFR with mortality have not been comprehensively evaluated in this population. RESEARCH DESIGN AND METHODS: This is a cohort study among Cardiovascular Health Study participants with diabetes, mean age 78 years. GFR was estimated using serum cystatin C and serum creatinine. Albumin-to-creatinine ratio (ACR) was measured in single-voided urine samples. RESULTS: Of 691 participants, 378 died over 10 years of follow-up. Cystatin C–estimated GFR <60 ml/min per 1.73 m(2), creatinine-based estimated GFR <60 ml/min per 1.73 m(2), and urine ACR ≥30 mg/g were each associated with increased mortality risk with hazard ratios of 1.73 (95% CI 1.37–2.18), 1.54 (1.21–1.97), and 1.73 (1.39–2.17), respectively, adjusting for age, sex, race, diabetes duration, hypoglycemic medications, hypertension, BMI, smoking, cholesterol, lipid-lowering medications, prevalent cardiovascular disease (CVD), and prevalent heart failure. Cystatin C–estimated GFR and urine ACR were additive in terms of mortality risk. Cystatin C–estimated GFR predicted mortality more strongly than creatinine-based estimated GFR. CONCLUSIONS: Albuminuria and impaired GFR were independent, additive risk factors for mortality among older adults with diabetes. These findings support current recommendations to regularly assess both albuminuria and GFR in the clinical care of patients with diabetes; a focus on interventions to prevent or treat CVD in the presence of albuminuria, impaired GFR, or both; and further consideration of cystatin C use in clinical care.