High Blood Pressure May Pose Higher Stroke Risk

Having high blood pressure occasionally may pose a higher risk of having a stroke than having consistently high readings. Doctors should not ignore one-off high blood pressure readings and consider blood pressure variability and maximum blood pressure as risk factors for stroke rather than just average blood pressure.

Current guidelines say that the priority is to lower blood pressure to reduce the risk of having a stroke, but the doctors should also take into account blood pressure variability and prescribe the drugs that result in the most steady blood pressure.

In the study the researchers' looked at high blood pressure and visit-to-visit blood pressure variability in four groups of 2,000 people each of whom had experienced transient ischemic attacks (TIAs), often dubbed "mini-strokes", considered warning signs of stroke risk.

They found that in each TIA cohort, the visit-to-visit variability in systolic blood pressure (SBP, the higher of the two blood pressure readings that a doctor takes, eg the 120 in a 120/80 reading) and maximum blood pressure were both strong predictors of subsequent stroke.

Those participants with the greatest variation in SBP over seven GP visits were six times more likely to have a major stroke and those with the highest blood pressure readings were 15 times more likely to have a stroke.

The researchers' concluded that:

Visit-to-visit variability in SBP and maximum SBP are strong predictors of stroke, independent of mean SBP.

The researchers' conducted a meta-analysis of 389 controlled trials and found that blood pressure variability was a probable explanation for why some types of drugs were more effective than others at preventing strokes.

In this second study, they concluded that:

Drug-class effects on interindividual variation in blood pressure can account for differences in effects of antihypertensive drugs on risk of stroke independently of effects on mean SBP.

And in a third study, the researchers' compared the effects of & blockers and calcium-channel blockers on blood pressure variability and how this might impact risk of stroke.

Previous studies have found that on the basis of mean blood pressure alone, calcium-channel blockers reduce the risk of stroke more than expected and & blockers less than expected. To prevent stroke most effectively, blood-pressure-lowering drugs should reduce mean blood pressure without increasing variability; ideally they should reduce both.