The Lancet has published the results of an analysis that has identified a correlation between stroke risk and variability or maximal in systolic blood pressure (SBP). This study has been reported in the general media (BBC).
The study noted that guidelines for the treatment and diagnosis of hypertension focus upon assessment of blood pressure over a time period, essentially providing an average over the time the readings are taken. This study aimed to assess stroke risk in comparison to visit-to-visit variability in SBP (expressed in standard deviations) or maximum SBP using data from the UK-TIA and ASCOT-BPLA studies.
The analysis founds that mean SBP, variability in SBP (as standard deviation, coefficient of variation and variation independent of the mean) all positively correlated with stroke risk. The correlations in variability remained after correction for mean SBP.
Additionally, it was noted that the association was strong individuals in the top decile of variability and this association grew stronger after correction for mean SBP, age, sex and other risk factors (Hazard Ratio [HR] 12.08, 95% CI 7.40-19.72, p<0.0001). Maximum SBP was also strongly correlated after correction for mean SBP (HR 15.01, 95% CI 6.56-34.38, p<0.0001).
The authors note that their findings do not prove causality and recommend that consideration be given to how visit-to-visit strong>variability in blood pressure might be integrated into clinical practice. Attention is also drawn to the "false reassurance of a few normal blood-pressure readings ".
Action: Clinicians should be aware of this study. While clinical guidelines are reviewed perhaps it would be prudent to give a little more weight to one-off high blood pressure readings.