Blood pressure and mortality in U.S. veterans with chronic kidney disease: a cohort study

Abstract

Background: The ideal blood pressure (BP) to decrease mortality rates in patients with non-dialysis-dependent chronic kidney disease (CKD) is unclear.

Objective: To assess the association of BP (defined as the combination of systolic BP [SBP] and diastolic BP [DBP] at the individual level) with death in patients with CKD.

Design: Historical cohort between 2005 and 2012.

Setting: All U.S. Department of Veterans Affairs health care facilities.

Patients: 651 749 U.S. veterans with CKD.

Measurements: All possible combinations of SBP and DBP were examined in 96 categories from lowest (<80/<40 mm Hg) to highest (>210/>120 mm Hg), in 10-mm Hg increments. Associations with all-cause mortality were examined in time-dependent Cox models with adjustment for relevant confounders.

Results: Patients with SBP of 130 to 159 mm Hg combined with DBP of 70 to 89 mm Hg had the lowest adjusted mortality rates, and those in whom both SBP and DBP were concomitantly very high or very low had the highest mortality rates. Patients with moderately elevated SBP combined with DBP no less than 70 mm Hg had consistently lower mortality rates than did patients with ideal SBP combined with DBP less than 70 mm Hg. Results were consistent in subgroups of patients with normal and elevated urinary microalbumin-creatinine ratios.

Limitation: Mostly male patients, inability to establish causality, and large number of patients missing proteinuria measurement.

Conclusion: The optimal BP in patients with CKD seems to be 130 to 159/70 to 89 mm Hg. It may not be advantageous to achieve ideal SBP at the expense of lower-than-ideal DBP in adults with CKD.

Primary funding source: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, and U.S. Department of Veterans Affairs.

Figure 1

Multivariable adjusted relative hazards (hazard ratios, 95% confidence intervals) of all-cause mortality associated with systolic blood pressure (Panel A) and diastolic blood pressure (Panel B) levels relative to a hypothetical patient with the mean level of time-varying SBP (133 mmHg) and DBP (71 mmHg), respectively, in time-dependent Cox models using restricted cubic splines, adjusted for age, gender, race, diabetes mellitus, cardiovascular and cerebrovascular disease, heart failure, the Charlson comorbidity index, medications (angiotensin converting enzyme inhibitors/angiotensin receptor blockers, alpha-, beta- and calcium channel blockers, loop and thiazide diuretics, and cholesterol lowering agents), estimated glomerular filtration rate and blood cholesterol. SBP, systolic blood pressure; DBP, diastolic blood pressure.

Figure 2

Forest plot of the multivariable adjusted mortality hazard ratios (95% confidence intervals) associated with blood pressure categories defined according to cutoffs established by the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. The group with systolic blood pressure <120 mmHg and diastolic blood pressure <80 mmHg served as referent. Estimates are from time-dependent Cox models adjusted for age, gender, race, diabetes mellitus, cardiovascular and cerebrovascular disease, heart failure, the Charlson comorbidity index, medications (angiotensin converting enzyme inhibitors/angiotensin receptor blockers, alpha-, beta- and calcium channel blockers, loop and thiazide diuretics, and cholesterol lowering agents), estimated glomerular filtration rate and blood cholesterol. CHF, chronic heart failure; CAD, coronary artery disease; eGFR, estimated glomerular filtration rate; UACR, urine microalbumin creatinine ratio