White coat hypertension

White coat hypertension (WCH or WCHT), and not to be confused with the white coat effect (WCE), is commonly defined as typical in-clinic blood pressure (BP) measurements of 140/90 mm Hg or more in the presence of multiple daytime out-of-clinic home or ambulatory BP readings averaging less than 135/85 mm Hg in untreated individuals ^1-4. 

Alternatively, mean 24-hour BP readings of less than 130/80 mm Hg have been proposed as the out-of-clinic cutoff value ^1,2.

Discrepancies and similarities from author to author between the definitions of WCE and WCH (and its synonyms) should be taken into account when examining this topic and each individual paper.

Terminology

Colloquially, white coat hypertension may be referred to as white coat syndrome. Alternatively, the terms isolated office hypertension or isolated clinic hypertension have been proposed as replacements as they more accurately represent the body of evidence with respect to the etiology and pathophysiology behind the currently popular term of white coat hypertension.

Epidemiology

Most patients with white coat hypertension experience elevated BP readings in-clinic versus out-of-clinic and most of these are hypertensive in and out of office to begin with.  However, a smaller subset of patients have normal BP readings out-of-office in conjunction with hypertensive measurements in a medical environment ¹.

Even so, most individuals with white coat hypertension have higher out-of-office BP readings than truly normotensive individuals ².

Overall, the prevalence of white coat hypertension appears to be approximately 9%-15.4% among patients with in-office hypertension but these values depend on the cut-off values used in each study and the study’s population ^5,9. 

White coat hypertension is most likely to occur in women and elderly patients ^5,6.

Pathology

The etiology and pathophysiology behind white coat hypertension (WCH) is not fully understood.

Traditionally, it has been believed that the sight of or interaction with a physician or the actual physical measurement of blood pressure (cuff inflation) brings about white coat hypertension as a result of an alarm reaction.

And so, as with other forms of hypertension, sympathetic overdrive occurs in cases of white coat hypertension ². 

But in at least one study it has been shown that the alerting reaction and pressor response to the physician’s visit does not accurately reflect the difference between in-clinic and daytime average blood pressure values.  Therefore, using such a difference as a measurement of the white coat effect is potentially erroneous ¹⁰.

Hence, the true reason behind white coat hypertension is not clear and still under investigation, while studies on the traditional explanations for WCH have largely negated their validity ^10,11. 

It is currently presumed that a multitude of behavioral and other modulating factors (yet to be fully elucidated) affect daytime and clinic BP and account for the actual clinic-daytime BP difference. ^1,2,10.

Treatment and prognosis

Between 10-30% of subjects with white coat hypertension develop sustained hypertension within 3-5 years and the percentage rises to 42.6% when reassessed 10 years later ^7,8.

In the long term, white coat hypertension may lead to an increased risk for stroke, cardiovascular events, and the development of diabetes mellitus ^1,2,9.