Prognostic significance of blood-pressure variability – Author's reply

Abstract

414 www.thelancet.com Vol 376 August 7, 2010 for pulse pressure as well as for SBP and results were similar. In the TIA cohorts and in ASCOT-BPLA, the association between visit-to-visit variability in pulse pressure and risk of stroke was, in fact, slightly weaker than was the association based on SBP. Adjustment for mean pulse pressure reduced the association between visit-to-visit variability in SBP and stroke risk less than did adjustment for mean SBP in all cohorts studied (unpublished data). However, patients in all of the cohorts that we studied were elderly and had either several vascular risk factors or symptomatic vascular disease, and so increased arterial stiff ness would have been highly prevalent. Findings might diff er in younger healthier cohorts. Joep Lagro and colleagues point out the potential importance of cerebrovascular reactivity in understanding the mechanisms of the association bet ween variability in blood pressure and stroke risk, assuming a causal link. In fact, this and other mechanistic issues were discussed in some detail in the accompanying Review. As was also discussed, the issue of determining how best to quantify variability in routine clinical practice is crucial. We showed that variability in daytime SBP on ambulatory monitor ing was partly correlated with visit-to-visit variability, as was variability in mean daytime SBP on repeated ambulatory monitoring. Visit-to-visit variability also correlates with variability in daily blood-pressure measurements at home (unpublished data) and with postural instability in blood pressure (unpublished data). Further research is needed to determine whether these diff erent measures of variability have similar or possibly add itive prognostic value.