Patients with chronic kidney disease and high blood pressure faced higher risk of coronary heart disease, stroke, kidney failure, and death than patients without high blood pressure, but that risk lessened with age, according to a new study.
Researchers analyzed the relationship of systolic blood pressure (SBP) and diastolic blood pressure (DBP) in nearly 340,000 veterans with chronic kidney disease and found that SBP of above 140 mm Hg was associated with an elevated risk of all the outcomes that they examined over 5 years. DBP, on the other hand, was not related to cardiovascular outcomes.
In addition, both DBP and SBP had a U-shaped association with mortality, according to lead author Csaba Kovesdy, MD, at the Memphis Veterans Affairs Medical Center in Tennessee. But older CKD patients with high pressures showed risks of serious cardiorenal adverse events that, while still higher than for nonhypertensive CKD patients, were somewhat lower than for younger hypertensive patients.
Kovesdy and colleagues published their findings in the Clinical Journal of the American Society of Nephrology.
"Our results reinforce that treatment of hypertension in younger patients with chronic kidney disease toward targets recommended by current clinical guidelines is paramount to improve outcomes in these patients," wrote the authors. "In very elderly patients with chronic kidney disease, a more cautious BP-lowering strategy may be reasonable."
The magnitude of the association between heightened SBP (≥170 mm Hg) and mortality decreased with age when compared with those with a lower SBP (130-139 mm Hg). The adjusted hazard ratios were:
- 1.95 (95% CI 1.34-2.84) for those younger than 50 years old
- 2.01 (1.75 -2.30) for those ages 50-59
- 1.68 (1.49-1.89) for those ages 60-69
- 1.39 (1.25-1.54) for those ages 70-79
- 1.30 (1.17-1.44) for those ≥80
The P value for that trend was <0.001. Data were drawn from the Racial and Cardiovascular Risk Anomalies in CKD study, focusing on a participant subset who developed CKD (stages 3A-5) following enrollment.
Mean age in the cohort was 69 at baseline, and 97% of the patients were male. Mean eGFR at baseline was 48. At baseline, patients with a higher SBP were more likely to be black and to have diabetes and hypertension; they were also less likely to have coronary heart disease, congestive heart failure, and chronic lung disease. Most patients were taking at least one anti-hypertensive medication.
Median follow-up after CKD diagnosis was 4.8 years, and total mortality was 63 per 1,000 patient-years. For all values of SBP and age that were tested, the lowest mortality was associated with having SBP of 120-139 mm Hg for patients who were younger than 80 years old and having SBP of 120-159 for patients ≥80 years.
Lower DBP was associated with higher mortality at all age groups; the groups with the lowest mortality had DBP of 70-79 mm Hg and were younger than 50 and had DBP of 80-89 and were ≥50 years old. The authors tested whether weight loss, low body mass index (BMI), or comorbidities affected the relationship, but the results remained largely similar. In addition, there was no consistent trend in associations between SBP or DBP and mortality among patients who had lost weight or had a low BMI in any age group.
In total, 9,450 patients experienced an incident coronary heart disease event and 14,557 patients had an incident ischemic stroke. For both of those groups, the rates were similar or lower for older patients compared with younger ones.
For end stage renal disease, the rates were lower in older compared with younger patients. Higher SBP was associated with greater risk of kidney failure at all ages, however. The hazard ratios associated with SBP ≥170 compared with 130-139 mm Hg varied by age:
- 7.59 (95% CI, 4.89-11.79) for <50
- 6.06 (4.93-7.47) for ages 50-59
- 7.07 (5.42-9.22) for ages 60-69
- 3.68 (2.37-5.72) for ages 70-79
- 2.95 (1.28-6.80) for ages ≥80
"The elderly are considered a special category, in part because of scarce clinical trial evidence in this population, and in part because of empirical and theoretical concerns over their tolerance of excessive BP lowering," wrote the authors.
They added that a possible explanation for seeing lower rates of mortality among some elderly patients is that there are competing threats that have nothing to do with blood pressure, like infections.
Limitations of the study include its observational nature, limiting inference about causal relationships. In addition, the findings may not be generalizable to other populations since the cohort consisted mostly of men, and there may have been confounders that could not be excluded.
The authors disclosed no relevant relationships with industry.
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