Being told you have high blood pressure can feel like a big deal - you'll probably have to take pills for the rest of your life and go to your GP regularly to check your blood pressure's under control.
There's not much you can do about the first bombshell, except remind yourself high blood pressure isn't so much a disease as a risk factor for other diseases, such as heart disease and stroke.
Why are many doctors still sniffy about patients measuring their own blood pressure at home?
But you might decide you're going to wrestle back some control by checking your blood pressure yourself at home, using an automatic blood pressure monitor.
They're easy to get hold of, reasonably priced (from about £40-£150), and you don't need to be a brain surgeon (or even a heart surgeon) to use one. No wonder sales of these devices are booming.
So why are many doctors still sniffy about patients measuring their own blood pressure at home? Is home monitoring a good idea or not?
Taking control or worrying yourself sick?
There are several reasons why your GP might be sceptical about self-monitoring.
It could be a hangover from earlier times when it meant doctors training patients in the complicated art and science of using a manual blood pressure device. Modern devices pose much less of a challenge.
Even automatic machines are open to bias: it’s easy to round figures down or simply ignore unusually high results. In my experience, this can apply equally to doctors, and some modern machines memorise readings so you can’t fiddle the records.
More simply, doctors worry that patients will worry. They worry some people will develop an obsessional and unhealthy interest in every peak and trough of their blood pressure. I’ve certainly seen people panicked unnecessarily by a one-off high reading.
But perhaps the main reason is that most automated blood pressure monitors on sale to the public haven't been properly validated, or have been shown to be inaccurate. The National Institute for Health and Clinical Excellence, which issues guidance for doctors, says using home-monitoring devices as part of primary care needs more research.
Golden rules of self-monitoring
Other doctors may have a different view, but if a patient of mine wanted to buy one of these devices this is what I hope they would do.
First, discuss it with me. We can talk about how to use the machine properly, how often and when to take readings, and how to interpret them. For example, the threshold for high blood pressure is generally lower using home monitors (more than 135/85 is high) than in the clinic (more than 140/90 is high).
Without getting too obsessive, when it comes to long-term monitoring I’ve found the European Society of Hypertension advice works well - take two morning and evening readings each day for one week every three months. Alternatively, you could take readings on one day every week.
Things that temporarily affect blood pressure
- Anxiety
- Exercise
- Meals
- Tobacco
- Alcohol
- Pain
- Time of year - blood pressure's generally lower in summer
- Time of day - blood pressure's usually lower when you're asleep
Second, before my patient handed over their hard-earned cash, I’d strongly advise them to check up-to-date information on which devices have been properly validated.
Just because a monitor is on sale - and even if it has a 'CE' mark (indicating it meets European standards) - it doesn’t necessarily mean it's accurate or reliable.
Luckily, this job is done for you by the British Hypertension Society.
Third, choose an upper arm monitor as these have been shown to be the most reliable, but always make sure you have the right sized cuff to fit your arm - too small or too large and the reading can be inaccurate.
In general, wrist and finger devices aren't recommended because they're easily influenced by changes in circulation, and the measuring cuff is not always at the level of your heart, which it should be.
Benefits of self-monitoring
Despite some doctors' reservations, the tide seems to be turning.
Self-monitoring can be useful in detecting white coat hypertension. This is a phenomenon affecting up to one in five adults, in which blood pressure measurements taken at your doctor's or in a clinic are high even though your blood pressure's normal the rest of the time.
The European Society of Hypertension and the US Joint National Committee reckon self-monitoring might work well in these cases because several readings, taken in your normal environment, can be averaged over time.
The latest guidance from the British Hypertension Society also says self-monitoring could encourage people to take their blood pressure medication.
Last but not least
Finally, if you buy a self-monitoring device get it properly checked and recalibrated every year or so. Check with the manufacturer if they'll do this for you and how much it'll cost. One manufacturer I asked quoted around £30 and recommends a check every two years.
With a bit of dialogue, you and your GP can both feel managing your blood pressure effectively is a team effort.
Dr Graham Easton works in a London GP practice with around 10,000 patients. It has three GP partners, three salaried doctors and fully computerised medical records. His medical training was at The Royal London Hospital. He's also an experienced medical journalist who has worked for BBC Radio Science and the British Medical Journal.
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