Albuminuria is an independent predictor of all-cause and cardiovascular mortality in the Japanese population: The Takahata study

Background: Albuminuria is a known risk factor for cardiovascular events and premature deaths. However, the association between urinary albumin excretion and mortality is unknown in the Japanese population. To clarify this, we conducted a community-based longitudinal study. Methods: This study included 3,445 registered Japanese subjects (mean age 62.6 years), with a 7-year follow-up. Albuminuria was defined as a urine albumin-creatinine ratio (ACR) ≥30 mg/g in the morning spot urine. Results: Subjects with albuminuria (n = 514, 14.9 %) were older and showed a higher prevalence of hypertension, obesity, and diabetes and lower values of estimated glomerular filtration rate (eGFR) than those without albuminuria (n = 2931, 85.1 %). During the follow-up, 138 subjects died. A Kaplan-Meier analysis showed that all-cause mortality significantly increased along with the increase in urine albumin excretion (log-rank test, P < 0.001). The subjects with albuminuria showed a significantly higher mortality rate than those without albuminuria (7.4 vs. 3.4 %; log-rank test, P < 0.001). A Cox proportional hazard model analysis after adjusting for possible confounders showed that albuminuria was an independent risk factor for all-cause and cardiovascular mortality (hazard ratio [HR] 1.69, 95 % confidence interval [CI] 1.12-2.56 and HR 2.27, 95 % CI 1.10-4.70, respectively) but not for noncardiovascular mortality. These associations were preserved after excluding subjects with high ACR (≥300 mg/g). Conclusions: Albuminuria was a risk factor for all-cause and cardiovascular mortality in the Japanese population. To detect subjects with a high risk for premature death, measuring urinary albumin excretion might be useful.