Albuminuria Increases All-Cause Mortality in Japanese Patients with Type 2 Diabetes Mellitus

Previous studies have reported that diabetic kidney disease is associated with cardiovascular events and death. Little is known about the independent association of albuminuria and estimated glomerular filtration rate (eGFR), with mortality in Asian patients with type 2 diabetes mellitus (T2DM) without renal failure. We conducted a historical cohort study to clarify this issue in Japanese patients with T2DM. In this study, we recruited 385 patients with T2DM, who never had chronic renal failure (eGFR < 30 mL/min/1.73 m(2) at baseline) and malignant diseases. With the end point of all-cause mortality, Cox regression analysis was performed. During the observational period of 7 years, 54 patients died. Cox regression analysis adjusted for confounding factors such as age, duration of diabetes, body mass index, and HbA1c, and showed that urinary albumin level was significantly associated with the mortality [hazard ratio (HR) = 1.32, 95% confidence interval (CI) = 1.03–1.70 per standard deviation (SD) increase, p = 0.031]. After additional adjustment for eGFR, the association remained significant (HR = 1.32, 95% CI = 1.02–1.70 per SD increase, p = 0.033). On the other hand, eGFR was not associated with the mortality. The present study showed that higher urinary albumin was associated with increased all-cause mortality in T2DM, independently of eGFR. These findings suggest that, regardless of eGFR, albuminuria is important for the increased risk of mortality in Japanese T2DM patients without chronic renal failure (eGFR < 30 mL/min/1.73 m(2)). However, because of several limitations, further large-scale longitudinal studies are necessary to confirm the present study.