It is not unusual for blood pressure measured in the doctor's office to be higher than blood pressure measured at home during normal activities. The more comfortable a person is with the office surroundings, the more likely the blood pressure in the office will be close to the blood pressure measured at home. However, it is estimated that 20-25 % of patients with mild hypertension in the doctor's office (140-160/90-104 mm Hg) have what is called "white-coat" or isolated office hypertension.
White coat hypertension is not as dangerous as sustained hypertension (hypertension which is present all the time). However, individuals who have white coat hypertension may have a higher risk of complications and cardiovascular disease than those with completely normal blood pressure all the time. Another risk of white coat hypertension is that individuals with this condition may develop sustained hypertension at a later time.
There are several reasons to identify white coat hypertension and to distinguish those individuals whose blood pressures are only elevated in the doctor's office and are normal at all other times. The most important reason is to prevent unnecessary treatment of hypertension. If blood pressure medication is prescribed to a person who only has elevated blood pressure in the doctor's office, then the treatment may cause low blood pressure at all other times, which may result in fatigue and light headedness. Second, it is also useful to identify whether blood pressure elevations are simply isolated to the doctor's office, or whether they are present at other times as well, for example, at work.
Ambulatory blood pressure monitoring is a technique that involves automated inflation of the BP cuff and recording of the BP at 15 to 20 minute intervals throughout the day and every 30 to 60 minutes during sleep. This technique permits identification of those with white coat hypertension. It also permits a more comprehensive assessment of the blood pressure profile of an individual throughout the day and night. These parameters are important in determining how to best treat hypertension.