Home blood pressure testing could reduce strokes

06 March 2018

Interview with

Jonathan Mant, University of Cambridge

High blood pressure is a strong predictor of heart disease and strokes, so finding a way to manage effectively it is a top priority for patients and doctors. Now, a team think they may have found a way to improve how we treat high blood pressure  without adding a huge cost or time burden: they’re using measurements people take themselves. Chris met up with study author Jonathan Mant to hear how...

Jonathan - About a third of people in the UK already measure their own blood pressure. But then, the problem is that GPs don’t really do anything with those readings, they tend to use the readings that they or their practice nurses take themselves. The question that we wanted to ask was if GPs systematically made use of the readings taken by patients at home, would that improve the blood pressure control?

Chris - Why should there be a difference between the measurements that I get at home versus if I came and sat in a GP’s surgery and got them to do it?

Jonathan - The measurements taken at home are paradoxically more reliable. This is because many people, when they go to the GP’s surgery, are a bit anxious about what their blood pressure might be so often their blood pressure is higher when they take it in the GP’s surgery.

Chris - It’s usually because they can’t find a car parking place.

Jonathan - Ha, yes absolutely. I suppose the other thing I should say about blood pressure measurement at home is that you could take blood pressure lots of times because what we’re aiming to treat when we’re trying to lower blood pressure is what the true underlying blood pressure is. If you just take one or two random readings in a clinic, that’s not a very accurate gauge of what the true underlying blood pressure is. But, at home, you can take it several times a day, several day at week and so, therefore, you do get a better representation of what the underlying blood pressure was.

Chris - How did you do the trial?

Jonathan - We recruited 140 General Practices and within those practices we recruited about 1,200 people who had high blood pressure, and then those 1,200 patients were randomly assigned to one of three groups. The first group was usual care, so the GP was left to manage their blood pressure in the normal way. The second and third groups were both given blood pressure machines to measure their blood pressure at home and they were trained how to use those machines. We asked them to take their blood pressure morning and evening every day for a week, one week per month. One group we asked to send the blood pressure reading back by post to the practice, the other third groups sent the blood pressure reading back by sms messaging.

Chris - So all this data is aggregated, what do you do with all that information?

Jonathan - Two things: the patients have a postcard system that warns them if their blood pressure is too high or too low. If they find their blood pressure is to high they’re encouraged by the postcard to go and see their General Practitioner. The practices were asked to review the readings they received every month and make appointments for people where they had concern. Then we asked the General Practitioners to titrate the blood pressure medications according to those blood pressures.

Chris - So the GPs are able to react to that information coming in and adjust the patient’s treatment but they haven’t, critically, had to take up an appointment space and had to see the patient while all those measurements were being made so this, potentially, sounds a lot more efficient then?

Jonathan - It’s a lot more efficient and it’s partly giving the control to the patient rather than to the GP, and the GP doesn’t have to measure the blood pressure at all.

Chris - When you then follow up and see what happens to blood pressures of these different groups of people, how do they all compare?

Jonathan - At six months, there was significantly lower blood pressure in the group that was self-monitoring and using text messages to get the information back to their GP. At twelve months, there was significantly lower blood pressure in both the self-monitoring groups.

Chris - The differences in blood pressure, were they clinically significant as in I could say well, something statistically significant the blood pressure is a very small amount lower, but actually that’s not really going to make a big different to my heart attack or stroke risk? Is it clinically significant here?

Jonathan - Yes it was. We found that the blood pressure in the self-monitoring groups was lower by 4 mm of mercury. Now that may not sound much but that equates into about a 20% reduction in the risk of stroke and about a 10% reduction in the risk of heart attack.


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