Renal tubular damage as an independent risk factor for all-cause and cardiovascular mortality in a community-based population: the Takahata study

Background: Renal tubular damage plays a crucial role in the development of end-stage kidney disease, a risk factor for cardiovascular events and mortality. However, the relationship between renal tubular damage and all-cause and cardiovascular mortality rates in the general population remains unclear. To address this gap, we conducted a cohort study in the general population using the urinary beta 2-microglobulin-creatinine ratio (UBCR) as a marker of renal tubular damage. Methods: This study included 3427 residents aged >= 40 years in Takahata, Japan. We examined the association between the UBCR values in single-spot urine samples at enrollment and all-cause and cardiovascular mortality rates within a median follow-up of 9.2 years. Results: The participants were divided into two groups based on their UBCR levels (< 300 mu g/g and >= 300 mu g/g groups). Kaplan-Meier analysis showed a significantly higher incidence of all-cause and cardiovascular mortality rates in the high UBCR group (log-rank P < 0.01). Multivariable Cox proportional hazards model adjusted for age, sex, estimated glomerular filtration rate (eGFR), urine albumin level, smoking, and comorbidities showed a significantly higher hazard ratio of 1.49 (95% confidence interval (CI) 1.10-2.03, P = 0.01) for all-cause mortality and a hazard ratio of 1.73 (95% CI 1.00-2.98, P = 0.048) for cardiovascular mortality in the high-UBCR group. The net reclassification index was significantly improved by adding a high UBCR to the conventional risk factors. Conclusion: UBCR is an independent risk factor for all-cause and cardiovascular mortality in the general population, independent of eGFR and urinary albumin levels.