The association of SBP with mortality in patients with stage 1-4 chronic kidney disease

Abstract

Objectives: Hypertension is a risk factor for chronic kidney disease (CKD) progression and mortality. However, the optimal blood pressure associated with decreased mortality in each stage of CKD remains uncertain.

Methods: In this retrospective cohort study, we included 13 414 individuals with CKD stages 1-4 from NHANES general population datasets from 1999 to 2004 followed to 31 December 2010. Multivariate analysis and Kaplan--Meier curves were used to assess SBP and risk factors associated with overall mortality in each CKD stage.

Results: In these individuals with death rates of 9, 12, 30 and 54% in baseline CKD stages 1 through 4, respectively, SBP less than 100 mmHg was associated with significantly increased mortality adjusted for age, sex and race in stages 2,3,4. After excluding less than 100 mmHg, as a continuous variable, higher SBP is associated with fully adjusted increased mortality risk in those on or not on antihypertensive medication (hazard ratio 1.006, P = 0.0006 and hazard ratio 1.006 per mmHg, P < 0.0001, respectively). In those on antihypertensive medication, SBP less than 100 mmHg or in each 20 mmHg categorical group more than 120 mmHg is associated with an adjusted risk of increased mortality. Increasing age, men, smoking, diabetes and comorbidities are associated with increased mortality risk.

Conclusion: For patients with CKD stages 1-4, the divergence of SBP above or below 100-120 mmHg was found to be associated with higher all-cause mortality, especially in those patients on antihypertensive medication. These findings support the recent guideline of an optimal target goal SBP of 100-120 mmHg in patients with CKD stages 1-4.

Figure 1.

Kaplan-Meier Curves of survival of 13,414 NHANES subjects with CKD followed from 1999 to 2010 shown by systolic blood pressure (SBP) levels at 20 mmHg intervals. A. Stage 1: 1428 patients. B. Stage 2: 9306 patients. C. Stage 3: 2471 patients. D. Stage 4: 209 patients.

Figure 1.

Kaplan-Meier Curves of survival of 13,414 NHANES subjects with CKD followed from 1999 to 2010 shown by systolic blood pressure (SBP) levels at 20 mmHg intervals. A. Stage 1: 1428 patients. B. Stage 2: 9306 patients. C. Stage 3: 2471 patients. D. Stage 4: 209 patients.

Figure 2.

Kaplan-Meier Curves of survival of 13,414 NHANES subjects with CKD followed from 1999 to 2010 shown by systolic blood pressure (SBP) levels at 20 mmHg intervals based on antihypertensive medication usage. A. No anti-hypertensive medication, 7299 patients*. B. On antihypertensive medication, 5327 patients*. * The total number of subjects is less than 13,414 because of patients with missing data for adjustment variables.