Associations of Systolic Blood Pressure With Incident CKD G3-G5: A Cohort Study of South Korean Adults

Abstract

Rationale & Objective: Clinical practice guidelines recommend a target blood pressure (BP) < 130/80 mm Hg to reduce cardiovascular risk. However, the optimal BP to prevent chronic kidney disease (CKD) is unknown. Study Design: Population-based retrospective cohort study. Setting & Participants: 10.5 million adults who participated in the National Health Insurance Service National Health Checkup Program in South Korea between 2009 and 2015 and had an estimated glomerular filtration rate (GFR) >= 60 mL/min/1.73 m(2) at the beginning of follow-up. Predictors: Baseline and time-updated systolic BP (SBP) as a continuous variable and categorized as <110, 110 to 119, 120 to 129, 130 to 139, or >= 140 mm Hg. Outcome: Incident CKD GFR categories 3 to 5 (CKD G3-G5), defined as de novo development of estimated GFR < 60 mL/min/1.73 m(2) for at least 2 consecutive assessments confirmed at least 90 days apart. Analytical Approach: Cox proportional hazards regression for baseline BP and marginal structural analysis for time-updated BP. Results: During 49,169,311 person-years of follow-up, incident CKD G3-G5 developed in 172,423 (1.64%) individuals with a crude event rate of 3.51 (95% CI, 3.49-3.52) per 1,000 person-years. Compared to a baseline SBP of 120 to 129 mm Hg, HRs for incident CKD G3-G5 for the <110, 110 to 119, 130 to 139, and >= 140 mm Hg categories were 0.84 (95% CI, 0.82-0.85), 0.92 (95% CI, 0.91-0.94), 1.11 (95% CI, 1.09-1.12), and 1.30 (95% CI, 1.28-1.31), respectively. For time-updated SBPs, corresponding HRs were 0.57 (95% CI, 0.56-0.59), 0.79 (95% CI, 0.78-0.80), 1.58 (95% CI, 1.55-1.60), and 2.49 (95% CI, 2.45-2.53), respectively. Treated as a continuous exposure, each 10-mm Hg higher SBP was associated with 35% higher risk for incident CKD G3-G5 (95% CI, 1.35-1.36). Limitations: Use of International Classification of Diseases codes to assess comorbid condition burden; residual confounding, and potential selection bias cannot be excluded. Conclusions: In this large national cohort study, higher SBPs were associated with higher risk for incident CKD G3-G5. These findings support evaluation of SBP-lowering strategies to reduce the development of CKD.