Systolic blood pressure and mortality among older community-dwelling adults with CKD

Abstract

Background: Chronic kidney disease (CKD) is an increasingly common condition, especially in older adults. CKD manifests differently in older versus younger patients, with a risk of death that far outweighs the risk of CKD progressing to the point that dialysis is required. Current CKD guidelines recommend a blood pressure target <130/80 mm Hg for all patients with CKD; however, it is unknown how lower versus higher baseline blood pressures may affect older adults with CKD.

Study design: Retrospective cohort study.

Setting & participants: Older patients (aged ≥ 75 years) with CKD (estimated glomerular filtration rate <60 mL/min/1.73 m(2)) in a community-based health maintenance organization.

Predictor: Baseline systolic blood pressure (SBP) < 130, 130-160 (reference group), and > 160 mm Hg.

Outcomes: Participants were followed up for 5 years to examine rates of mortality (primary outcome) and cardiovascular disease hospitalizations (secondary outcome).

Results: At baseline, 3,099 participants (38.5%) had SBP < 130 mm Hg, 3,772 (46.9%) had SBP of 131-160 mm Hg, and 1,171 (14.6%) had SBP >160 mm Hg. A total of 3,734 (46.4%) died and 2,881 (35.8%) were hospitalized. Adjusted HRs for mortality in the groups with SBP < 130 and > 160 mm Hg were 1.22 (95% CI, 1.11-1.34) and 1.06 (95% CI, 0.93-1.22), respectively. Adjusted HRs for cardiovascular hospitalization in these groups were 1.10 (95% CI, 0.99-1.23) and 1.26 (95% CI, 1.09-1.45), respectively.

Limitations: Although causality should not be inferred from this retrospective analysis, results from this study can generate hypotheses for future randomized controlled trials to investigate the relationship between blood pressure and outcomes in older patients with CKD.

Conclusions: Our study suggests that lower baseline SBP (≤ 130 mm Hg) may predict poorer outcomes in terms of both mortality and cardiovascular hospitalizations in older adults with CKD. Conversely, higher baseline SBP (> 160 mm Hg) may predict increased risk of cardiovascular hospitalizations, but does not predict mortality. Clinical trials are required to test this hypothesis.

Figure 1

Study design and derivation of the cohort.

Figure 2

Kaplan-Meier curve for mortality in original cohort (death versus time). The thick dark line represents the lowest blood pressure cohort (SBP<130 mmHg); the other two blood pressure cohorts (SBP 131-160 and SBP >160 mmHg) are superimposed on the upper line.