Introduction: Long-term variability in systolic blood pressure (SBP) is associated with higher risk of cardiovascular events. Little is known about the association between within-visit SBP variability and stroke.
Hypothesis: Higher within-visit SBP variability is associated with higher odds of stroke.
Methods: Participants included adults ≥18 years who participated in the US National Health and Nutrition Examination Surveys from 1999 to 2010. Stroke was self-reported. SBP was obtained up to four times by a physician, using a manual sphygmomanometer according standardized procedures. Within-visit SBP variability was defined as standard deviation of the BP measurements, stratified into quartiles. We evaluated the relationship between within-visit SBP variability and odds of having had a stroke using multivariable logistic regression.
Results: Of the 27,987 adults, 16.4% were aged ≥ 65 years, 51.3% were female, 71.2% were White, 10.7% were Black and 7.9% were Mexican American. Factors associated with higher mean SBP variability included older age, hypertension, chronic kidney disease, peripheral artery disease, and smoking (all P<0.05). The prevalence of stroke significantly increased across SBP variability quartiles from 2.1% for quartile 1 to 3.7% for quartile 4. High SBP variability was associated with higher odds of stroke (OR 1.8, 95% CI 1.4-2.2). After adjustment for covariates, the odds ratio of stroke comparing highest vs. lowest quartile of SBP variability was 0.9 (p=0.400).
Conclusions: Within-visit variability in SBP is associated with increased odds of stroke but the relationship is confounded by age and covariates.