January 23, 2018
Measuring blood pressure

White Coat Hypertension: 6 Things to Know

by Jeanine Barone  

For some people, going to the doctor is an inherently anxiety-ridden experience. So it’s perhaps not surprising that when the doctor measures their blood pressure, it’s high—even if they otherwise have normal blood pressure. This phenomenon is known as white coat hypertension, defined as blood pressure readings over 140/90 when measured by a doctor but lower when measured at home. An estimated 15 to 30 percent of people with high blood pressure in the doctor’s office have white coat hypertension. Here’s what you need to know about this condition.

1. What causes it?

Typically, it’s caused by people being anxious at the doctor’s office, possibly over what their blood pressure reading will be or over the act of having their blood pressure taken itself. Indeed, people with white coat hypertension tend to have higher anxiety levels at the doctor’s office not only compared with people who have normal blood pressure, but also compared with those who have persistent hypertension. Interestingly, people prone to white coat hypertension are not necessarily any more anxious in their overall lives than the average person. They seem to overreact specifically when they are in the doctor’s office. Age is another risk factor for white coat hypertension, which occurs more frequently in older people.

2. Does it happen only in medical offices?

Usually, but not always. The condition is called “white coat” because blood pressure spikes in the doctor’s office or other medical settings where a physician (or other health care provider) is measuring blood pressure. But there are also cases in which blood pressure might be elevated if one doctor measures your blood pressure but not another doctor. In some people, blood pressure is not elevated if a nurse or technician measures it as opposed to a doctor, or if the person wearing an ambulatory monitor (which measures blood pressure every 20 to 30 minutes over a day or two and stores the readings) as opposed to having the reading taken by a medical professional.

Anxiety about blood pressure can lead to a vicious cycle in which higher and higher blood pressures at the doctor’s office lead patients to obsessively measure their blood pressure at home. This in turn can lead to more anxiety and possibly artificially high readings even at home, making it difficult to get a true measure of the individual’s blood pressure.

3. How long does it usually take for articificially elevated blood pressure to return to normal?

It varies. If white coat hypertension is suspected, your doctor may wait 20 minutes or so and recheck your blood pressure, which may have gone down since the first reading. The problem may also lessen with subsequent visits. For instance, if a person has white coat hypertension when first visiting a new doctor, it may significantly drop by the third visit. But in some patients it could take half a dozen visits for blood pressure to stabilize. If blood pressure is 140/90 or higher on at least three separate office visits, it’s generally recommended that the patient undergo ambulatory monitoring before blood pressure-lowering medications are prescribed.

Various measurement errors can also lead to abnormally high blood pressure readings and are commonly made at doctor’s offices. These include using the wrong size blood pressure cuff, talking while blood pressure is being taken, and not resting for the recommended 10 to 15 minutes before having blood pressure measured. For more on getting a correct blood pressure reading, see Blood Pressure: Getting it Right.

4. Does white coat hypertension carry any health risk?

Many medical experts see white coat hypertension as a benign condition. But a study published in the Journal of the American College of Cardiology in 2015 suggested that it is linked with an increased risk of cardiovascular disease. The researchers looked at data from the large Dallas Heart Study and followed the subjects, including those with white coat hypertension, for nine years. They found an increased risk of stroke, heart attacks, heart failure, and other signs of cardiovascular disease in people with white coat hypertension compared with those who had normal blood pressure readings at the doctor’s office.

However, another study published in the same journal a year later found different results. After looking at data on more than 1,300 subjects from 11 different studies, the researchers found that white coat hypertension carried a risk for cardiovascular disease only among older people (over 60 years) who already were at high risk because they had at least three risk factors such as diabetes, high cholesterol, a history of cardiovascular disease, smoking, or obesity. Among those who were at low risk, those with white coat hypertension were no more likely to develop cardiovascular disease than those with normal blood pressure. The authors concluded that doctors should focus on treating those older patients who have white coat hypertension but are also at high risk for heart disease.

Clearly, more studies need to be done to determine exactly how white coat hypertension affects health risk. In any case, the higher risk of cardiovasculardisease linked with white coat hypertension is well below that seen with sustained hypertension.

5. Should white coat hypertension be treated?

There’s no agreement as to whether white coat hypertension needs to be treated. It may, in fact, be harmful to prescribe anti-hypertensive medication if blood pressure is normal when measured at home. That’s because, under those circumstances, the medication could cause your blood pressure to fall too low, putting you at risk for fainting.

6. Can people have normal blood pressure in the doctor’s office but not at home?

Yes. That’s referred to as masked hypertension, a name that conveys that the doctor isn’t getting an accurate picture of a patient’s blood pressure. Numerous studies have found that masked hypertension increases the risk of cardiovascular disease, compared with consistently normal blood pressure. It’s not clear what causes blood pressure to spike at home rather than at the doctor’s office, but possible reasons include stress, not taking prescribed anti-hypertensive medication consistently until the person has a doctor’s visit, or possibly drinking coffee right before a reading at home. Any of the measurement errors mentioned above could also apply.

The 2015 study from the Journal of the American College of Cardiology that looked at white coat hypertension also looked at masked hypertension, finding that both doubled the risk for cardiovascular disease compared with normal blood pressure. If you have normal blood pressure in the doctor’s office but you’ve ever found your blood pressure to be high when you’ve measured it at home, tell your doctor, who should suggest regular home monitoring or ambulatory monitoring to get a complete picture of your blood pressure.

Also see High Blood Pressure: Your Questions Answered.