How Significant Is White Coat Hypertension?

White coat hypertension (WCH) is defined as an elevated office blood pressure (BP) >140/90 mm Hg and out‐of‐office BP readings <135/85 mm Hg. Many patients are anxious when visiting a physician’s office and BP readings may reflect this by being initially elevated but decreasing after subsequent office visits. Sequential studies have shown that in patients with high BP readings on a first visit to a new physician, there is a mean 15/7 mm Hg fall in systolic BP (SBP) and diastolic BP (DBP) by the third visit, with some patients not reaching stable BP values until the 6th visit. ¹ Having BP taken in the office by a nurse or medical assistant decreases the white coat effect. ² Based on this, it is often recommended that patients with new‐onset mild to moderate increases in BP not be diagnosed or treated for hypertension unless BP remains elevated after 3 to 6 visits unless there is evidence of target organ damage.

Ambulatory blood pressure monitoring (ABPM) is an excellent diagnostic tool to diagnose WCH and is useful in avoiding the initiation of unnecessary medication. WCH is one of the few diagnostic codes that is reimbursed for the application or use of ABPM.

The prevalence of WCH varies from 10% to about 20% of patients and is more common in children and the elderly. ³ , ⁴ When office DBP is >105 mm Hg it is very uncommon that this is due to WCH. ⁵

WCH also occurs in treated hypertensive patients with apparent resistant hypertension. In a study of nearly 500 treated hypertensive patients (with more than 60% of patients on ≥3 antihypertensive medications), 37% had normal BP on ABPM. ⁶

Patients with WCH often develop sustained hypertension. In a study of 81 patients with elevated office BP (mean 154/97 mm Hg) and normal 12‐hour ambulatory BP (mean 125/77 mm Hg), 60 patients had a mean ambulatory BP >140/90 mm Hg after 5 to 6 years of follow‐up. ⁷ In a recent 10‐year follow‐up of the Metabolic Syndrome in the Pressioni Arteriose Monitorate E Loro Associazioni (PAMELA) study of 1412 patients in Italy, 16.1% of patients had WCH at first examination. At 10‐year follow–up, 42.6% of the WCH developed into sustained hypertension. Although initial drug therapy is avoidable in WCH, vigilance is required because of the high likelihood of developing sustained hypertension. ⁸

Whether patients with WCH have an increased risk of cardiovascular events is controversial. In the Hypertension and Ambulatory Recording Venetia Study (HARVEST), echocardiography was performed in 119 patients with WCH, 95 normotensive age‐ and sex‐matched controls, and 603 patients with stage 1 hypertension. The left ventricular mass index was 82, 89, and 94 in the normotensive, WCH, and sustained hypertensive groups, respectively. ⁹ Another study evaluated 6000 patients with normotension and included 140 persons with WCH. ¹⁰ Patients were followed for a median of 5.4 years. Rate of stroke per 100 patient‐years was 0.35, 0.59, and 0.65 in normal, WCH, and hypertensive patients, respectively. The adjusted hazard ratios of stroke, however, were significantly increased in the hypertensive group but not in the WCH group. This was further confirmed in a recent meta‐analysis by Fagard, which showed the risk of cardiovascular events to not be significantly different between normotensive and WCH patients, whereas outcomes were worse in patients with masked and sustained hypertension. ¹¹

Risk of cardiovascular events still seems fairly low and therefore reinforces the rationale that treatment is not currently indicated in patients with WCH. Many of these patients, however, will go on to develop sustained hypertension and therefore lifestyle measures should be actively encouraged in all these patients and regular follow‐up should be encouraged to detect the onset of sustained hypertension. It also makes sense that home BP monitoring is a useful tool to recommend to these patients as outlined in the Call to Action of the late Thomas Pickering. ¹²