February 15, 2007 — Individuals with stages 3 to 4 chronic kidney disease (CKD) had a J-shaped relationship between systolic blood pressure (BP) and incident stroke, such that those with the lowest systolic blood pressure were at significantly increased risk compared with those with a systolic BP of 120 to 129 mm Hg. These findings, from a secondary analysis of pooled data from the Atherosclerosis Risk in the Community Study (ARIC) and the Cardiovascular Health Study (CHS), are published in the March issue of the Journal of the American Society of Nephrology.
Lead author Daniel E. Weiner, MD, from Tufts-New England Medical Center in Boston, Massachusetts, explained to Medscape that CKD is a leading health problem and stroke is the third leading cause of death in the United States, but although hypertension is a risk factor for stroke in the general population, dialysis patients have a higher risk for death as systolic BP drops below around 130 to 150 mm Hg. He added: "That’s dramatically different from what's been described in the general population; in individuals who are otherwise healthy who have coronary artery disease, the lower the blood pressure drops, the better they do."
The group aimed to assess whether this altered relationship between systolic blood pressure and incident stroke, which is seen in dialysis patients, also exists in individuals with moderate kidney disease. They examined pooled data from ARIC and CHS, 2 community-based, longitudinal studies.
The 20,358 individuals studied had a mean age of 59.2 ± 10.2. A total of 1549 individuals (7.6%) had stage 3 or 4 CKD, defined as an estimated glomerular filtration rate (GFR) of 15 to 60 mL/min per 1.73 m2. Patients were stratified into the following predetermined baseline systolic blood pressure categories: less than 120, 120 to 129, 130 to 139, 140 to 159, and 160 or higher mm Hg. During a median follow-up of 111 months, 1029 individuals (5.1%) had a stroke.
Different Risk Pattern in CKD Patients
Among individuals with CKD, those with a systolic BP less than 120 mm Hg had a significantly increased risk for incident stroke compared with those with systolic BP of 120 to 129 mm Hg (HR, 2.51; 95% CI, 1.30 – 4.87); those with a systolic BP greater than 120 mm Hg were still at increased risk. This pattern was not seen among individuals without CKD: their risk for stroke increased with rising systolic BP, at all blood pressure levels.
"We know that the more we lower systolic BP, the more that we slow CKD progression, so it would be unwise to say that we don’t want to treat blood pressure, " Dr. Weiner summarized. He added: "What this says is that there may be some risk when we very aggressively treat blood pressure." He noted that possibly some individuals with moderate CKD might have very severe underlying illness, and low BP is just a marker of that illness that makes them more likely to have a stroke. On the other hand, perhaps BP is being lowered too far. What is needed is a prospective study to examine specific blood pressure goals and the risks associated with achieving or not achieving those goals, he concludes.
J Am Soc Nephrol. 2007;18:960-966.
Medscape Medical News © 2007
Cite this: Marlene Busko. Low Systolic BP Linked to Increased Stroke Risk in Patients With Moderate CKD - Medscape - Feb 15, 2007.