Is White-Coat Hypertension Harmless?

Summarized by Robert W. Griffith, MD
September 12, 2005

Introduction

Most people have heard about "white-coat hypertension" - it's when your blood pressure reading is raised at the doctor's office or in the clinic, but is normal when you measure it at home. It's also normal when measured by a monitor worn during the day (so-called "ambulant pressure").

There have been some reports that white-coat hypertension isn't entirely benign. However, it's generally agreed that ambulatory pressure (pressure measured when you are leading your normal life) gives a better idea of the outcome after controlling blood pressure with medication; this suggests that people with white-coat hypertension have better prospects than those with sustained hypertension. The actual risk associated with white-coat hypertension hasn't been established, but a new report from Japan proves some valuable indication. It's published in the Archives of Internal Medicine and we summarize it here.¹

What was done

Scientists are conducting a study of blood pressure in 2,700 people over 40 in Ohasama, Japan. Self-blood pressure readings at home were made by 1900 of these subjects, after they'd received appropriate instruction. After excluding those who didn't have office measurements, those who took antihypertensive drugs, and those who actually had "home hypertension", there were 972 participants remaining. Of these, 777 took part throughout the follow-up period, and formed the final study participants.

The follow-up period lasted more than 8 years; participants took an average of 24 home pressure measurement. At baseline, 649 participants had normal blood pressure at home and at the doctor's ("sustained normotension"), while 128 had white-coat hypertension.

What was found

Of the 649 participants with sustained normotension at baseline, 144 (22%) developed home hypertension or were started on antihypertensive medication during the follow-up period. And of the 128 subjects with white-coat hypertension at baseline, 60 (47%) developed home hypertension or started medication during the 8 years of the study.

Analyses showed that the higher the home blood pressure, the sooner home hypertension developed; thus those participants with a baseline home blood pressure of108/52 mmHg or lower had a less than 5% chance of developing home hypertension.

The likelihood of white-coat hypertension to progress to home hypertension was 2.8 times that for sustained normotension people. The likelihood was higher in older people, men and obese persons.

What these findings mean

If your health professional takes your blood pressure and tells you "It's probably only white-coat hypertension", and "we'll check it again next time you come in", don't be satisfied. Even if you buy a sphygmomanometer and get normal readings at home, you are still twice as likely to develop hypertension needing treatment as someone without white-coat hypertension.

The findings in this study suggest that white-coast hypertension is an transitional condition that goes on to become home hypertension, and requires addressing with the appropriate measures: lower your salt intake, watch your weight, exercise more, and eat plenty of fiber, fruit and veggies. Then, if and when your readings show you and your doctor that it's necessary, take your antihypertensive medication religiously. It's worth it!

Source

• White-coat hypertension as a risk factor for the development of home hypertension. T. Ugajin, A. Hozawa, T. Ohkuba,  et al., Arch Intern Med, 2005, vol. 165, pp. 1541--1546

Footnotes
1. White coat hypertension was defined as home blood pressure below 135/85 mmHg, and office blood pressure 140/90 mmHg or above. If the pressure was below 135/85 mmHg at home and below 140/90 mmHg at the office, it was defined as 'sustained normotension'.

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