Comparison of the predictive ability of albuminuria and dipstick proteinuria for mortality in the Japanese population: the Yamagata (Takahata) study

Background: Albuminuria and proteinuria are known risk factors for premature death. This study compared the ability of albuminuria and proteinuria to predict mortality in a community-based population. Methods: We evaluated the urinary albumin creatinine ratio (ACR) and proteinuria by dipstick at a baseline survey and examined the association between the 7-year mortality and three categories (albuminuria [ACR ≥ 30 mg/g], trace proteinuria, and ≥[1+] proteinuria) in 3446 Japanese subjects at a local health check. Results: Albuminuria, ≥trace proteinuria, and ≥(1+) proteinuria were identified in 514 (14.9 %), 290 (8.4 %), and 151 (4.4 %) subjects, respectively. There were 138 deaths during the follow-up period, including 41 cardiovascular deaths. A Kaplan–Meier analysis showed that all-cause mortality significantly increased along with the increase in ACR and proteinuria levels (log-rank P < 0.01). The mortality rate (deaths per 1000 person-year) was higher in subjects with albuminuria (12.8), ≥trace proteinuria (12.6), and ≥(1+) proteinuria (16.2) than in all subjects (6.9). A Cox proportional hazard model analysis showed that all three categories were significant predictors of all-cause mortality in the unadjusted model, although after adjustment for possible confounders, a significant association was observed only with albuminuria. Albuminuria, but not proteinuria, was a significant predictor of cardiovascular mortality in both the unadjusted and adjusted models. Conclusion: Albuminuria had a high prevalence and was strongly associated with mortality, as compared with proteinuria by dipstick, suggesting that albuminuria might be a superior predictor of poor prognosis in the Japanese population.