Orthostatic Blood Pressure Changes Could Add to Stroke Risk

Marked changes in blood pressure (BP) when people move from a supine to a standing position may be predictive of stroke, according to a new study.

Researchers at the University of Minnesota (Minneapolis, USA) investigated the association of orthostatic BP change (within 2 minutes after supine to standing repositioning), reviewing data from 12,817 participants enrolled in the Atherosclerosis Risk in Communities (ARIC) study during a median of 18.7 years of follow-up. During this period, the participants suffered 153 lacunar, 383 nonlacunar, and 144 cardioembolic strokes.

The researchers found a significant U-shaped (quadratic) association between orthostatic systolic BP change and lacunar stroke risk, although differences between categories of systolic BP change were nonsignificant after accounting for confounders. Nonlacunar stroke risk increased by 5% with an orthostatic decrease in systolic BP of between 10 and 20 mmHg, compared with stable orthostatic systolic BP; a decrease of 20 mmHg or more in orthostatic BP increased nonlacunar stroke risk 2.02-fold and cardioembolic stroke risk 1.85-fold.

Orthostatic diastolic BP decrease was associated with increased risk of nonlacunar thrombotic and cardioembolic strokes; the hazard ratios associated with 10 mm Hg lower orthostatic diastolic BP (continuous) were 1.26 and 1.41, respectively, in fully adjusted models. These associations were independent of confounders, which included age, gender, education, antihypertensive use, smoking status, resting heart rate, waist circumference, heart failure, and atrial fibrillation. The study was published early online on January 4, 2011, in Hypertension.

"One clinical implication of the present findings is the potential usefulness of identifying and controlling orthostatic blood pressure increase, as well as decrease,” concluded lead author Hiroshi Yatsuya, MD, and colleagues of the division of epidemiology and community health. "However, it is possible that orthostatic BP change is a marker for other known or unknown conditions such as autonomic dysfunction or other underlying comorbidities, and measures for controlling orthostatic BP change are not well established.”

Orthostatic hypotension, also known as postural hypotension, orthostasis, and colloquially as head rush or a dizzy spell, is a form of hypotension in which a person's BP suddenly falls when the person stands up. It is primarily caused by gravity-induced blood pooling in the lower extremities, which in turn compromises venous return, resulting in decreased cardiac output and subsequent lowering of arterial pressure.

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