How Does Intensive SBP Control Affect Renal Function in People Without Kidney Disease?
By Will Boggs MD
NEW YORK (Reuters Health) - Small declines in kidney function associated with intensive systolic blood pressure (SBP) control are outweighed by reduced risks of cardiovascular and all-cause mortality, according to results from the SPRINT research group.
“Although intensive treatment resulted in an increased incidence of chronic kidney disease (CKD), the average difference in eGFR (estimated glomerular filtration rate) between the two treatment groups was quite small (about 3 mL/min/1.73m2),” Dr. Srinivasan Beddhu from University of Utah School of Medicine, Salt Lake City, told Reuters Health by email. “Indeed, as asymptomatic incident CKD is much more benign than heart attack, stroke, or death, the risks of incident CKD are outweighed by the potential cardiovascular benefits of intensive SBP lowering.”
In SPRINT, targeting SBP below 120 mmHg (vs. <140 mmHg) was associated with 25% lower cardiovascular disease (CVD) event risk and 27% lower all-cause mortality but with a 3.5-fold increased incidence of new CKD.
Dr. Beddhu and colleagues performed detailed analyses of SPRINT, focusing on differences in mean eGFR, incident CKD (a >30% decrease in eGFR to below 60 mL/min/1.73m2), and all-cause death or cardiovascular events in patients without preexisting CKD.
After 6 months, SBP was a mean 15 mmHg lower in the intensive-control group than in the standard-control group, according to the September 5 Annals of Internal Medicine online report.
During this same interval, mean eGFR with intensive control declined by 3.32 mL/min/1.73m2 more than with standard control. The difference increased to 4.50 mL/min/1.73m2 at 18 months and remained relatively stable through month 42.
Incident CKD events emerged in 4.2% of patients in the intensive-control group, versus only 1.1% in the standard-control group. The number needed to treat for 3 years to produce 1 incident CKD event was 38.
By the final study visit, 25.7% of intensive-control patients with incident CKD had recovered normal renal function (vs. 10% of those in the standard-control group). None progressed to end-stage renal disease.
Compared with standard control, intensive control reduced the risk of the composite of a primary CVD event or all-cause death by 29% (from 2.51 to 1.78 events per 100 person-years), the risk of a primary CVD event by 33% (from 1.92 to 1.28 events per 100 person-years), and the risk of all-cause death by 26% (from 1.05 to 0.77 events per 100 person-years). The corresponding numbers needed to treat were 46, 57, and 108, respectively.
“Intensive SBP lowering is feasible and decreases cardiovascular events and death when carefully applied, even in high-risk groups such as the elderly,” Dr. Beddhu concluded.
Dr. Jorge Polonia from Faculty of Medicine of Porto, University of Porto, in Portugal, who recently investigated the annual deterioration of renal function in hypertensive patients with or without diabetes, told Reuters Health by email, “SPRINT excluded many patients such as patients with prior stroke, diabetes, or with severe renal insufficiency with severe proteinuria, or with cardiac failure (with ejection fraction below 35%) or with bad compliance. Thus, the population included represents no more than 15% of the population with high blood pressure.”
“With respect to the absence of benefit and even worsening of renal events with the lowering of blood pressure, I believe it may have to do with the type of renal patients included,” he said. “Since the study excluded diabetics and patients with proteinuria, it may have been included preferably subjects with renal disease of ischemic type which admittedly are more sensitive to blood pressure reduction.”
He is also troubled by the fact “that SPRINT is an open study (less credibility in science than a double blind randomized controlled trial) and was stopped early.”
Dr. Polonia sees these problems as “a great threat to its generalizability and practical applicability.”
SOURCE: https://bit.ly/2wHUhVv
Ann Intern Med 2017.
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