Measuring blood pressure is a tricky business. Measure some people’s while they are in a doctor’s surgery and it will be deceptively high; others will be misleadingly low. According to research fellow Dr James Sheppard, it is very much “a variable thing – if you rely on a one-off reading, it might be unusually high or low”, given that levels fluctuate throughout the day.
The British Heart Foundation (BHF) estimates as many as 7 million people in the UK have undiagnosed hypertension – referred to as the “silent killer” because it is often without obvious symptoms – although there’s no way of telling whether so many remain undiagnosed because they are not being tested, or because they are giving artificially low readings. The common outcome is vulnerability to conditions such as heart attacks and strokes, so we should welcome new research published by Oxford University that looks at ways of calculating our true blood pressure reading by overcoming problems experienced in a clinical setting.
One explanation for misreadings, “white-coat syndrome”, might sound like something out of The X-Files, but it’s the simple idea that the stress around a doctor’s visit can cause artificially high blood pressure. But, according to Emily Reeves, a senior cardiac nurse at the BHF, there are ways to mitigate this: “It sounds silly, but it’s about trying to control your anxiety … taking a few minutes out and having a deep breath.”
But could there be an anti-white coat effect, too? Some reports have suggested, off the back of Sheppard’s research, that patients may be so calmed by the presence of medical professionals, with their clipboards and charming bedside manners, that it is causing their blood pressure to read lower than it actually is.
But Sheppard is not convinced. Inaccuracies, he says, are often just bad luck. Or, for instance, “if someone has a job that involves lots of physical activity, their blood pressure might generally be high during the daytime, then at the doctor’s they’re more relaxed than in their daily routine”.
“In an ideal world,” says Sheppard, “we’d do 24-hour blood pressure monitoring on everybody” – but this is expensive and uncomfortable. Instead, his team has learned to recognise who might be most at risk – men, for example, and those previously diagnosed with high blood pressure – and created an algorithm that will warn health professionals if there is a higher chance of “a masked effect [such as] reverse white coat syndrome”.
Reeves, who was also “baffled” by the idea of anyone being calmed by a white coat – “I guess different people find different things relaxing” – says that over-40s should go for regular NHS health checks in any case, to make sure their hearts aren’t working harder than they should be.
