White-coat effect responsible for almost 40 percent of resistant hypertension

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While sitting at the physician’s office, some people may become anxious as they await their looming encounter with The Doctor. The phenomenon is common enough that health care professionals have even coined a term for it — white-coat syndrome — since it may manifest as an increase in blood pressure (BP) or heart rate. But a new study from the University of Barcelona actually crunches the numbers and finds that white-coat syndrome accounts for up to 37 percent of the diagnoses of resistant hypertension.

Data collected on 68,045 patients from the 2009 Spanish Ambulatory Blood Pressure Monitoring Registry (ABPM) identified 8,295 people as having resistant hypertension, meaning they had a BP reading greater than or equal to 140 mm Hg systolic and/or 90 mm Hg diastolic while on three or more BP medications. Patients wore a device that measured their BP at home every 20 minutes over a 24-hour period, called ambulatory BP recording. Those whose BP remained elevated were truly resistant, while those whose readings were normal at home were diagnosed with “white-coat” hypertension.

Following an observation period, about 63 percent of patients were diagnosed with true resistant hypertension, and patients in this group were also more likely to smoke and have diabetes, cardiovascular disease, enlarged hearts, and kidney dysfunction.

Commenting on the results, ACSH's Dr. Gilbert Ross thinks this is an excellent study because “by measuring blood pressure values at home, you are eliminating the white-coat effect,” but he also believes that “the number of people with non-resistant hypertension who are responding well to a single antihypertensive drug far outweigh the number of people not responsive to three drugs. I wonder how many such patients also suffer from the white-coat syndrome?”

Noting that hypertension is a serious risk factor for cardiovascular disease and death, ACSH's Dr. Elizabeth Whelan emphasizes that, “If you have trouble diagnosing it accurately, its treatment gets even more complicated.”