In a study of 651,749 U.S. veterans with CKD, Csaba P. Kovesdy, MD, from the Memphis Veterans Affairs Medical Center, and colleagues analyzed all possible combinations of systolic BP (SBP) and diastolic BP (DBP) from lowest to highest in increments of 10 mm Hg.
Compared with the reference BP value (140-149/80-89 mm Hg), BPs of 130-159/70-89 mm Hg were associated with the lowest mortality risk, which did not differ significantly from the reference value in adjusted analyses, Dr. Kovesdy’s team reported in Annals of Internal Medicine (2013;159:233-242). Below DBP of 70 mm Hg, lower SBP was associated with higher mortality rates, and SBP less than 120 mm Hg was associated with higher mortality rates regardless of the accompanying DBP, the study found.
The study population consisted of 132,249 individuals with normal BP (SBP below 120 and DBP below 80 mm Hg), 295,937 with prehypertension (SBP 120-139 or DBP of 80-89 mm Hg), 169,416 with stage 1 hypertension (SBP 140-159 or DBP of 90-9 mm Hg), and 54,147 with stage 2 hypertension (SBP of 160 mm Hg or higher or DBP of 100 mm Hg or higher).
In a fully adjusted model, patients who had normal BP had the highest mortality risk and those with stage 1 hypertension had the lowest mortality risk compared with patients who had prehypertension (the reference group).
“Clinical trials are needed to inform us about the idea BP target for antihypertensive therapy in patients with CKD,” the authors concluded. “Until such trials become available, low BP should be regarded as potentially deleterious in this patient population, and we suggest caution in lowering BP to less than what has been demonstrated as beneficial in randomized, controlled trials.”
The researchers observed that their study is notable for its large size, but they acknowledged some shortcomings. The study was observational, so only associations, and not causal relationships, can be established from it. “Specifically, we cannot conclude that the mortality risk associated with various BPs in our study is equal to the risk imparted by the same BPs when they occur as a result of antihypertensive interventions in clinical practice,” the authors wrote.
In addition, their cohort consisted of U.S. veterans who were almost exclusively men, so the findings may not apply to women or the general population, they pointed out.