White Coat Syndrome

The scale of it is the striking part. Studies repeatedly indicate that between fifteen and thirty per cent of people thought to have mild hypertension on the basis of clinic or office recordings show normal blood pressure otherwise, and no unusual response to a pressure stimulus.

Why the person does not look frightened

The detail that separates this from every phobia in the catalogue is that people with white coat hypertension do not display signs of trepidation, and the raised blood pressure is frequently not accompanied by a raised heart rate. Whatever is happening is not a panic response and would not be visible to a clinician looking for one.

No characteristic has been found that marks out who is susceptible. Age does not predict it.

What masked hypertension inverts

Masked hypertension is the same phenomenon inverted: blood pressure above the normal range during ordinary life and normal in the clinic. It is the more dangerous of the two, because the reading that reassures is the wrong one, and it is far less common. In one Turkish study of four hundred and thirty-eight consecutive patients, thirty-eight per cent were normotensive, forty-three per cent had white coat hypertension, two per cent had masked hypertension and fifteen per cent had sustained hypertension.

That distribution is worth reading twice. In that sample, white coat hypertension was three times commoner than a genuine diagnosis.

Why the measurement is so fragile

The list of things that corrupt a clinic reading is long and mostly mechanical:

• variability in the individual's own blood pressure
• technical inaccuracy
• an inadequate cuff size on the sphygmomanometer
• recently ingested substances that raise pressure
• talking during the measurement The anxiety of the patient is one item among those rather than the whole explanation.

Automated measurement over fifteen to twenty minutes in a quiet part of the clinic reduces the error without eliminating it. Ambulatory monitoring across a day, and home self-measurement, are increasingly used to tell the two apart, and a 2006 study of ninety-eight patients found home monitoring as accurate as twenty-four-hour ambulatory monitoring for determining blood pressure levels. Ambulatory monitoring is described as the more practical and reliable method overall and as better at predicting damage to organs.

Neither is clean. Daytime ambulatory readings take in the stresses of ordinary life by design, which means they also take in physical activity, stress and how much the person slept. Breathing patterns have been proposed as another route to identifying the effect.

Whether it counts as a disease

The position taken in the material is careful and worth stating exactly. People with white coat hypertension have lower morbidity than people with sustained hypertension, and higher morbidity than people who are clinically normotensive. It sits between the two rather than resolving into either, and the diagnosis and treatment of it remain described as controversial.

Even patients already taking medication for sustained hypertension, and normotensive at home, may show the effect in the office.

Where it touches the rest of this catalogue

The signs of iatrophobia listed in the medical fear literature include elevated blood pressure in clinical settings, which folds white coat hypertension into a phobia it is not identical to. Most people with the white coat effect do not describe themselves as frightened of doctors, and the absence of tachycardia argues that they are not having a fear response at all. What the two share is a setting.