The new findings suggest the phenomenon may affect a third of patients who appear not to be responding to drugs for high Blood Pressure, or hypertension.  Researchers made the discovery after monitoring the blood pressure of almost 70,000 patients with diagnosed hypertension as they went about their daily lives.

In total, 37 per cent of around 8,000 patients previously found to be resistant to treatment turned out to have 'white coat syndrome'.  Their blood pressure rose when they visited the doctor, giving the misleading impression that their treatment was not working.

Researchers asked patients to wear a portable device that takes blood pressure readings every 20 minutes day and night. The procedure is known as 'ambulatory blood pressure monitoring'.  Study leader Dr Alejandro de la Sierra, from the University of Barcelona in Spain, said: 'Physicians should be encouraged to use ambulatory monitoring to confirm resistant hypertension in their patients as it would ensure the most effective treatment options are used.

'Patients benefit by knowing whether their blood pressure is normal during daily activities or still needs the reinforcement of dietary and drug measures.'  The research, published in the American Heart Association journal Hypertension, showed that more women than men - 42 per cent compared with 34 per cent - were affected.

Patients with "true" resistant hypertension included higher numbers of smokers, diabetics and individuals with heart conditions.  'Those with true resistant hypertension showed high blood pressure at work, during the day and at night,' said Dr De la Sierra.  'The true resistant group also was more likely to have blood pressures that abnormally rose during the night when they were sleeping.'  Ellen Mason, senior cardiac nurse at the British Heart Foundation, said: 'High blood pressure increases the risk of having a heart attack or stroke and so treating high blood pressure, whether through lifestyle changes or medication, is vital.  'This study looked at a minority of people who still had high blood pressure despite being on at least three drugs to treat it.

'Visiting the doctor seemed to make some people falsely appear resistant to the effects of these drugs so the study was helpful in trying to identify which people seemed to be truly resistant and therefore more at risk of organ damage.  'It also adds weight to new draft guidelines to include a home blood pressure test for hypertensive patients here in the UK.

'More worryingly though, nearly half of us who do have high blood pressure in the UK are not being treated for it.  While the increasing use of home blood pressure monitoring is helpful for some, it will not target those who are unaware of the silent condition because it may have been many years since they had their blood pressure taken or because they simply think they are not at risk.'  The National Institute for Health and Clinical Excellence (Nice), which issues guidelines on NHS treatments, has proposed that people with two high blood pressure readings should take a third at home to rule out 'white coat syndrome'.

Source: Daily Mail