Kidney and Cardiovascular Outcomes in Older Population with Mildly to Moderately Decreased Kidney Function: A Nationwide Cohort Study

Introduction: Although the prevalence of chronic kidney disease (CKD) is increasing in the aging population, the clinical relevance of the CKD definition (glomerular filtration rate [GFR] <60 mL/min/1.73 m2) in older populations remains debatable. We investigated the clinical outcomes in older populations with mildly to moderately decreased GFR (45-59 mL/min/1.73 m2, CKD stage 3A). Methods: A total of 7,789,242 participants aged ≥40 years with estimated GFR (eGFR) ≥45 mL/min/1.73 m2 in national health screening examination from 2012 to 2017 were included in this retrospective cohort study using the Korean National Health Insurance Service database. The main outcomes included kidney failure, cardiovascular disease (CVD), and all-cause death. Cox regression hazard models were used to estimate the hazard ratios. Results: The proportion of participants with eGFR 45-59 mL/min/1.73 m2 was 10.0% and 16.3% in the old (65-74 years) and very old (75≥ years) groups, respectively. Mildly to moderately decreased eGFR was associated with a higher risk of kidney failure, CVD, and allcause death compared with eGFR 60-89 mL/min/1.73 m2 in the old and very old groups, regardless of proteinuria (adjusted hazard ratio [95% confidence interval] in the very old group without proteinuria: kidney failure 3.048 [2.495-3.722], CVD 1.103 [1.066-1.142], and all-cause death 1.172 [1.144-1.201]). Conclusion: Mildly to moderately decreased eGFR was associated with an increased risk of kidney failure, CVD, and all-cause death in the older population, regardless of proteinuria, suggesting the importance of appropriate monitoring and management in this population.