Blood pressure variations matter

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Large blood pressure variations over months may increase stroke risk
12/03/2010

New research published in The Lancet suggests that people whose blood pressure varies widely between high and normal over many months may require treatment for high blood pressure because they may be at increased risk of stroke.

The research suggests that people who have high blood pressure that is very high sometimes and normal at other times - over the space of many months (and possibly even years) - may also need treatment to lower their blood pressure. This is because they appear to be at increased risk of stroke when compared with people whose blood pressures were more consistent over time. However, other studies will be needed to prove that this suggestion is correct.

At the moment high blood pressure is defined as consistently having a blood pressure that is equal to or higher than 140/90 (140 over 90) over many weeks. (It isn't necessary for both numbers to be higher than they should be, if just one of them is consistently high, this is defined as high blood pressure.)

In addition, a second study appears to show that certain blood pressure medicines - known as calcium-channel blockers and diuretics - are better at helping to smoothe out variations in blood pressure levels than other medicines. Putting the two studies together, it suggests that people with blood pressures that vary greatly over many months and years may benefit from taking a calcium-channel blocker or diuretic to help control their blood pressure.

How large were the changes in blood pressure?

The variations in blood pressure that caused concern were those where people's top blood pressure (systolic) number changed by 20 or more between readings. These are quite large changes in blood pressure levels. (More common changes in blood pressure levels of 5-10 were not found to be important.)

How often were the blood pressure readings taken?

The researchers were looking at blood pressure readings taken over space of many months and years (although one set of results did look at readings taken over the space of 24 hours). Their particular interest was to see if people who sometimes had blood pressure levels that were below high blood pressure when they visited their doctor, but were sometimes much higher at other GP visits, needed help to keep their blood pressure under control.

The results showed that variability between GP visits of weeks and months had the strongest association with increased risk of stroke. Large variations over the space of 24 hours had a weaker association with increased risk.

Will this research change how blood pressure is treated?

At the moment, the research will not change how high blood pressure is treated in the UK. However, the findings will be taken into account when the next set of UK treatment guidelines are published.

The Blood Pressure Association's view

Professor Graham MacGregor, Chairman of UK charity the Blood Pressure Association, said: “This research shows for the first time that it’s not just the level of blood pressure, but the variability of blood pressure which is important in determining the risk of stroke.

“Based on this evidence it would seem sensible that variability of blood pressure is taken into account when someone is being considered for treatment.

“However, it’s important to remember that everyone’s blood pressure naturally fluctuates throughout the day, and a one-off high reading isn’t necessarily cause for concern.

“This study may alter the way we assess and treat high blood pressure in the future, but more research is needed before that would happen.

“Other research has shown that calcium-channel blockers and long-acting diuretics seem to be most effective in reducing such variability and therefore the risk of stroke. So it’s reassuring that current guidelines which already effect the majority of people being treated for high blood pressure, already recommend this treatment in the first instance.”

What is the current advice to people with high blood pressure, or are concerned by this research?

If you already have high blood pressure: Experts are keen to point out that this research does not change how people who have been diagnosed with high blood pressure will be treated. If you are taking tablets to lower your blood pressure, it is vital that you do not stop taking them.

If you have a one-off high blood pressure reading: A one-off high reading isn't necessarily a cause for concern. There are many reasons why your blood pressure could be high for a very short period of time - from having just run for the bus, to drinking a coffee or having a full bladder. For this reason, your doctor will want to check your blood pressure again in a few weeks' time to see if it is still high.

If your blood pressure remains consistently high over a number of weeks, then you may need treatment to lower your blood pressure. This might include taking blood pressure medicines.

If your blood pressure goes back down to a normal reading at the second check a few weeks later, then your doctor may wish to follow your blood pressure over the next few years, measuring every six months or so. The research suggests that if your top blood pressure (systolic) changes regularly by 20 or more over this time, then you may need treatment to smoothe out the variations in your blood pressure.


References:

Comment on the new research: Bo Carlberg, Lars Hjalmar Lindholm. Stroke and blood-pressure variation: new permutations on an old theme. The Lancet 2010; 375 (9718): 867-69.
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(10)60351-0/fulltext

Review of the research: Professor Peter M Rothwell. Limitations of the usual blood-pressure hypothesis and importance of variability, instability, and episodic hypertension. The Lancet 2010; 375 (9718): 938-48.
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(10)60309-1/fulltext

Lancet study into blood pressure variability: Prof Peter M Rothwell, Sally C Howard, Eamon Dolan, Prof Eoin O'Brien, Joanna E Dobson, Prof Bjorn Dahlöf, Prof Peter S Sever, Neil R Poulter. Prognostic significance of visit-to-visit variability, maximum systolic blood pressure, and episodic hypertension. The Lancet 2010; 375 (9718): 895-905.
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(10)60308-X/fulltext

Lancet study into blood pressure medicines and blood pressure variability: Alastair JS Webb, Urs Fischer, Ziyah Mehta, Prof Peter M Rothwell. Effects of antihypertensive-drug class on interindividual variation in blood pressure and risk of stroke: a systematic review and meta-analysis. The Lancet 2010; 375 (9718): 906-15.
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(10)60235-8/fulltext


Topics: Research, High Blood Pressure in the news, Medicines, Lifestyle, Measurement


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