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Relationship Between Systolic Blood Pressure and Mortality After Stroke | Journal Scan
Study Questions:
What is the effect of baseline systolic blood pressure (SBP) on all-cause and vascular mortality in patients with a history of stroke?
Methods:
The primary outcome of this study was all-cause mortality. Vascular mortality was a secondary outcome. The authors used data from the 1998-2004 National Health and Nutrition Examination Surveys (NHANES) to capture SBP and stroke diagnosis. SBP was measured in a standardized way at a single outpatient visit and divided into three categories: low-normal (<120 mm Hg), normal (120-140 mm Hg), and high (≥140 mm Hg). Stroke was defined as self-reported physician diagnosis of stroke. Deaths, through 2006, were identified through the National Death Index, which is linked to NHANES data. Vascular deaths were identified based on International Classification of Diseases (ICD)-10 codes. Univariate and multivariate analyses were used to examine the associations between SBP and all-case and vascular mortality. Covariates included age, poverty:income ratio, diabetes, coronary artery disease, and smoking.
Results:
There were 455 subjects with self-reported stroke included in the analyses; 50% had high SBP, 31% had normal SBP, and 19% had low-normal SBP. At 2 years, all-cause mortality was highest in the low-normal SBP group (11.5%), followed by the normal SBP group (8.5%), and high SBP group (7.6%). The pattern was similar for vascular mortality, with the highest risk in the low-normal SBP group (5.0%) and the lowest risk in the high SBP group (4.1%). With time, the association between SBP and mortality reversed. At 6 years, all-cause mortality was highest in the high SBP group (36.5%), with lower mortality in the normal (30%) and low-normal (19.6%) SBP groups. Vascular mortality had a similar pattern at 6 years, with the highest risk in the high SBP group (20.2%) and the lowest risk in the low-normal SBP group (9.1%). In the adjusted analyses, when compared with subjects in the high SBP group, subjects in the low-normal SBP group had higher all-cause mortality (adjusted hazard ratio [AHR], 1.96; 95% confidence interval [CI], 1.13-3.39) and a trend toward higher vascular mortality (AHR, 2.08; 95% CI, 0.93-4.68). Older age and poverty were associated with increased all-cause and vascular mortality.
Conclusions:
In subjects with a history of stroke, those with SBP of <120 mm Hg had higher all-cause mortality and a nonsignificant trend toward higher vascular mortality than those with SBP ≥140 mm Hg.
Perspective:
Treating high BP is an important part of stroke secondary prevention. Prior studies have shown that low as well as high SBPs are associated with increased mortality. The optimal SBP after stroke is unclear. This study uses data from a large cross-sectional survey to evaluate the relationship between SBP and mortality in stroke survivors. After adjustment, subjects with low-normal SBP had higher all-cause mortality than subjects with high SBP. While lower SBPs are generally better in terms of reducing mortality, there is likely a threshold effect where this benefit reverses. Guidelines recommend individualizing BP targets after stroke, by aiming for SBP <130 mm Hg in patients with lacunar stroke and SBP <140 mm Hg in others. Additional studies are needed to determine the lower boundaries of SBP within this range.
Keywords: Blood Pressure, Vascular Diseases, Stroke, Stroke, Lacunar, Mortality, Coronary Artery Disease, Coronary Disease, Hypertension, Nutrition Surveys, Smoking, Diabetes Mellitus, Systole, Multivariate Analysis, Secondary Prevention, Metabolic Syndrome
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