As many as 30 percent of patients experience this phenomenon
By David Dunaief, M.D.
White-coat hypertension (high blood pressure) is defined as blood pressure that is elevated to at least 140/90 mm Hg at a physician’s office, but “normal” when measured at home. The blood pressure considered normal at home for most Americans is less than 135/85 mm Hg. This is a real phenomenon caused by the anxiety or stress of being in a doctor’s office. It is also known as “isolated office hypertension.”
About 15 to 30 percent of patients experience white-coat hypertension (1). However, when the diastolic (bottom number) blood pressure is greater than 105 mm Hg, it is unlikely to be simply caused by doctor’s office-related stress (2).
What are the consequences of white-coat hypertension? The first challenge is that physicians may overtreat it, prescribing medications that lead to low blood pressure when not in the office. Alternately, we sometimes discount it because it seems benign or harmless. However, some studies show that it may increase the risk of sustained hypertension, which is a major contributor to developing cardiovascular disease — heart disease and stroke.
It is very important to take white-coat hypertension seriously because Centers for Disease Control and Prevention data show that the percentage of adults age 20 and over with hypertension reached 33.5 percent in the 2013-14 period (3).
What can be done?
What can be done about white-coat hypertension? Well, it does not need to be treated with medication, except potentially in elderly patients (over 80 years of age) but should involve lifestyle modifications, including dietary changes, stress reduction and exercise. In terms of diet, increased beet juice, green leafy vegetables and potassium, as well as decreased sodium intake may be important. You should monitor the blood pressure at home, taking multiple readings during the day, or by 24-hour ambulatory blood pressure readings, which require wearing a monitor. The latter provides the additional advantage of blood pressure readings during your sleep.
If you do monitor your blood pressure at home, the American Heart Association has suggestions on how to get the most accurate readings, such as measurements early in the morning before exercising and eating, as well as in the evening (4). You should also be comfortably seated, don’t cross your legs, and sit/relax for a few minutes before taking a reading. Let’s look at the evidence.
Risk of sustained high blood pressure
There were no substantial studies demonstrating any consequences from white-coat hypertension until 2005. Most previous studies on white-coat hypertension were not of long enough duration.
In the 2005 population-based Ohasama study, results showed that the participants who had white-coat hypertension were 2.9 times more likely to develop sustained hypertension, compared to those who had normal blood pressure in the doctor’s office (5). There were almost 800 participants involved in this study, with a mean age at the start of 56. What was really impressive about the study was its duration, with an eight-year follow-up. This gives a better sense of whether white-coat hypertension may develop into sustained hypertension. The researchers concluded that it may lead to a less than stellar outlook for cardiovascular prognosis.
Another study, published in 2009, reinforced these results. The PAMELA study showed that those with white-coat hypertension had about a 2.5-times increased risk of developing sustained high blood pressure, compared to those who had normal readings in all environments (6). There were 1,412 participants involved in the study, ranging in age from 25 to 74. Just like the previous study, an impressive aspect was the fact that there was a long follow-up period of 10 years. Thus, this was a substantial study, applicable to the general population over a significant duration.
Prevention of sustained hypertension
In a small, randomized controlled trial, beet juice was shown to reduce blood pressure significantly (7). Patients either were given 250 ml (about 8 ounces) of beet juice or comparable amounts of water. The patients who drank the beet juice saw an 11.2 mm Hg decrease in blood pressure, while those who drank water saw a 0.7 mm Hg reduction. This effect with the beet juice continued to remain significant. Even after 24 hours, there was a sustainable 7.2 mm Hg drop in blood pressure, compared to readings taken prior to drinking the juice. Although these results are encouraging, we need to study whether these effects can be sustained over the long term. Also, this study was done in patients with high blood pressure. I don’t know of any prevention studies done in patients with white-coat hypertension.
The researchers believe the effect is caused by high nitrate levels in beet juice that are converted to nitrite when it comes in contact with human saliva. Nitrite helps to vasodilate, or enlarge blood vessels, and thus helps to decrease blood pressure in a similar way as some antihypertensive (blood pressure) medications. The authors go on to surmise that green leafy vegetables offer protection from cardiovascular disease in part due to increased nitrite levels, similar to those in beet juice.
A subsequent double-blind, placebo-controlled clinical trial with 68 hypertensive patients found that blood pressure was significantly reduced in the clinic and in home readings over a four-week period, when compared to nitrate-free beet juice (8).
If you have diabetes, prediabetes, a family history or a high risk for diabetes, I recommend eating beets instead, since drinking beet juice will raise your sugar levels.
Increasing potassium levels significantly through food sources, not supplements, has a profound effect in reducing blood pressure. In a study where 3,500 to 4,700 mg of potassium were consumed through foods, the systolic (top number) blood pressure was reduced by 7.1 mm Hg (9). We should be getting 4,700 mg of potassium daily, which equates to about 10 bananas daily. Almonds, raisins and green leafy vegetables, such as Swiss chard, also have significant amounts of potassium.
White-coat hypertension should not be neglected. It is important to monitor blood pressure at home for at least three days with multiple readings, and then send them to your physician for review. Though patients don’t need to be on blood pressure medications at this stage, it does not mean you should be passive about the process. Make lifestyle modifications to reduce your risk of developing sustained hypertension.
(1) Hypertension. 2013;62:982-987, originally published Nov 13, 2013. (2) J Hypertens. 2001;19(6):1015. (3) cdc.gov. (4) Am Fam Physician. 2005 Oct 1;72(7):1391-1398. (5) Arch Intern Med. 2005 Jul 11;165(13):1541-1546. (6) Hypertension. 2009; 54: 226-232. (7) Hypertension. Online 2013; April 15. (8) Hypertension. 2015 Feb; 65(2): 320–327. (9) BMJ. 2013 Apr 3;346:f1378.
Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, visit www.medicalcompassmd.com or consult your personal physician.