Time-updated systolic blood pressure and the progression of chronic kidney disease: a cohort study.

Background: Previous reports of the longitudinal association between achieved blood pressure (BP) and end-stage renal disease (ESRD) among patients with chronic kidney disease (CKD) have not incorporated time-updated BP with appropriate covariate adjustment. Objective: To assess the association between baseline and time-updated systolic blood pressure (SBP) with CKD progression. Design: Observational, prospective cohort study. (ClinicalTrials.gov: NCT00304148) Setting: 7 U.S. clinical centers. Patients: Patients in the Chronic Renal Insufficiency Cohort Study (n = 3708) followed for a median of 5.7 years (25th to 75th percentile, 4.6 to 6.7 years). Measurements: The mean of 3 seated SBP measurements made up the visit-specific SBP. Time-updated SBP was the mean of that and all previous visits. Outcomes were ESRD and the composite end point of ESRD or halving of the estimated glomerular filtration rate. Analyses investigating baseline and time-updated SBP used Cox proportional hazards models and marginal structural models, respectively. Results: Systolic blood pressure was 130 mm Hg or greater at all visits in 19.2% of patients. The hazard ratio for ESRD among patients with SBP of was 1.46 (95% CI, 1.13 to 1.88) using only baseline data and 2.37 (CI, 1.48 to 3.80) using time-updated data. Among patients with SBP of 140 mm Hg or greater, corresponding hazard ratios were 1.46 (CI, 1.18 to 1.88) and 3.37 (CI, 2.26 to 5.03) for models using only baseline data and those using time-updated data, respectively. Limitation: Blood pressure was measured once annually, and the cohort was not a random sample. Conclusion: Time-updated SBP greater than 130 mm Hg was more strongly associated with CKD progression than analyses based on baseline SBP.