In young subjects with borderline elevation of conventional blood pressure, identification of white coat hypertension can be of considerable importance in avoiding undue penalties for insurance and employment. No one group seems to be exempt from the white coat phenomenon it may affect the young, the elderly, normotensive and hypertensive subjects, and pregnant women. It is best demonstrated by ambulatory blood pressure measurement (ABPM). White coat hypertension is a condition in which a normotensive subject becomes hypertensive during blood pressure measurement, but pressures then settle to normal outside the medical environment.
Its importance in practice is that decisions to lower blood pressure, and especially to administer drugs, should never be made on the basis of measurements taken in circumstances where the defence reaction is likely to be present. The degree of this reaction varies greatly from patient to patient, being absent in many, and it is usually reduced or abolished altogether with reassurance and familiarisation with the technique and circumstances of blood pressure measurement. It may occur in normotensive and hypertensive subjects. It is commonly seen in the accident and emergency departments of hospitals when patients are frightened and extremely anxious, but it may also occur in family doctors' surgeries and in the outpatients department. This may be regarded as a physiological reaction, often referred to as the “fight and flight” phenomenon, or “defence” or “alarm” reaction. Anxiety raises blood pressure, often by as much as 30 mm Hg.
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