White coat syndrome is a phenomenon whereby patients go to see their GP or a doctor in a hospital, and the stress they feel at seeing a medical professional causes their blood pressure to rise and gives them a high reading. This reading can be misleading and their true underlying blood pressure may be normal – but it may lead to them being given treatment to lower their blood pressure, or to avoid a stroke, that they don’t really need.
Blood pressure readings are composed of two figures, one above the other. The top figure is the systolic reading, which is the maximum pressure of the blood when the ventricles in the heart are contracting. This goes above the diastolic reading, which is the relaxation phase of the heartbeat. A normal, healthy figure is something like 120/70 or 120/80. High blood pressure is a systolic reading or 140 or more and/or a diastolic reading of 90 or more.
Research has estimated that as many as 15%-30% of patients who go to their GPs to have their blood pressure measured can suffer from White Coat Syndrome. They may be people who naturally suffer from anxiety but it’s not limited to these people, and not everybody who is anxious will have white coat syndrome. Research has shown female patients are more likely to suffer from it, even though they very often have a normal body mass index and are at low risk of having a heart attack or a stroke.
White Coat Syndrome is not easy to overcome, because if the same people were to take their own blood pressure at home rather than going to a GP or hospital, the chances are their reading would be absolutely normal. They can do it with a monitor they buy from a local pharmacy or a doctor can give them a monitor that automatically takes readings over a 24-hour period. The average of these readings taken in a normal setting in their usual environment would very likely be under 140/90 and give a more accurate picture of their true underlying blood pressure.
"Blood pressure is a very variable thing. It goes up and down all through the day"
That’s why a few years ago the National Institute for Health and Care Excellence (NICE) in the UK recommended that all patients who repeatedly record readings over 140/90 at the GPs’ surgery should be given one of these 24-hour monitors to use at home to check their blood pressure really is high and it isn’t just a white coat phenomenon. It’s now being done in other parts of the world as well. The US has recently recommended a similar approach.
Blood pressure is a very variable thing. It goes up and down all through the day. A reading at a GP’s can only be a very small snapshot and can catch it when it’s low or when it’s really high – and if white coat syndrome is involved it’s very likely to be the latter.
"Doctors should always sit them down for at least five minutes to allow them to rest and relax before taking the reading"
There is some evidence that patients become habituated to blood pressure management. The more it is measured, the more they become used to it. Quite often in clinical trials they measure blood pressure at the trial and again at the end, and the blood pressure goes down simply because the patients in the trial are getting used to having their blood pressure measured on multiple occasions.
Doctors can try to help patients suffering from white coat syndrome. They should always sit them down for at least five minutes to allow them to rest and relax before taking the reading, and rest their arm on a table. They should never talk to the patient while the reading is being taken because the patient talking can increase blood pressure. It might also help, rather than taking one reading in the clinic, to take three and take an average of them to get a more accurate indication.
White Coat Syndrome is not actually harmful as such to the patient’s health – it is just a measurement error. But it can be problematic in that it can lead to misdiagnosis and then mistreatment, and also doctors may decide not to carry out certain medical procedures or operations if a blood pressure reading is 140/90 or so. That’s why, ultimately, the best way to circumvent a white coat phenomenon is to do the reading yourself, over 24 hours, at home.