For all its life-saving potential, a blood pressure reading isn't necessarily as straightforward as you'd think.
For some people, the stress of having their blood pressure tested at a doctor’s office is enough to elevate the reading, leading to higher numbers than they'd get if they measured their blood pressure at home. This is called "white coat hypertension" or "white coat syndrome," so-named for the doctor’s white coat that supposedly inspires anxiety in patients.
Others have the opposite reaction: Stressful situations or unhealthy behaviors at home spike blood pressure, only for it to return to normal levels at the stress-free doctor’s office. This is called "masked hypertension," because doctors aren’t getting an accurate picture of just how high a person's blood pressure can get outside the clinic.
While these situations may seem like polar opposites, they each hide the truth about the actual state of a person’s blood pressure. And according to a new study by researchers at the University of Texas Southwestern Medical Center, people who fall into either category are at a higher risk of heart attack, heart failure, stroke and some types of organ damage than people who have normal blood pressure.
Patients with one of the two conditions were about twice as likely to have a cardiovascular event within the study's nine-year timeframe as those with normal blood pressure, according to the study.
The researchers analyzed a dataset of about 3,000 diverse adults in Dallas. Two home visits and a visit to the hospital determined that 3.3 percent of them had white coat hypertension, while 17.8 percent of them had masked hypertension.
These results held even when researchers excluded people with a history of cardiovascular disease or other risk factors for cardiovascular disease, including diabetes. They also controlled for age, sex, ethnicity, body mass index, smoking habits and cholesterol levels.
Senior study author Dr. Wanpen Vongpatanasin noted that this is the first study to demonstrate the risk of organ damage and long-term cardiovascular risk for a diverse population of people with white coat or masked hypertension.
Almost one in five of the study’s participants had masked hypertension, which isn’t as well known as white coat hypertension. The fact that so many people could be screening as “normal” at the doctor’s office while actually having blood pressure spikes at other times means that physicians could be missing diagnoses and failing to connect people with life-saving blood pressure medication.
Previous research on white coat hypertension has suggested that its danger is over-treatment, meaning people who don't really have hypertension are given blood pressure medication that they don't really need. But this latest study suggests that white coat hypertension could actually be a sign that someone is susceptible to full-blown hypertension later in life -- and that it may lead to worsening cardiovascular health over time.
Vongpatanasin noted that anyone whose blood pressure inches up in response to a stressful doctor’s visit will more often than not respond in a similar way to other stressful events in his or her life.
"If I had to guess, they’re more likely to have elevated blood pressure in response to stress," said Vongpatanasin, an internal medicine professor at UT Southwestern. "And then later on, when they have it long enough for whatever reason, they progress to the real hypertension that we can recognize."
The truly surprising finding came from the high percentage of people with masked hypertension. Vongpatanasin suggested that more people should monitor their blood pressure at home, where they face more stressful situations or do things like smoke or drink.
"The bottom line is that the physician should recommend the patient to monitor the blood pressure at home,” she concluded. "Just doing it in the clinic might not tell the whole story."
Past research on masked hypertension estimated it at vastly different rates depending on the populations studied. In a small study of young adults, only 2.1 to 4.4 percent of people had the condition, but a study of black Americans estimated it at 25.9 percent (Vongpatanasin's cohort was 50 percent black). The study most in line with Vongpatanasin’s finding is an international cohort of middle-aged people, which estimated masked hypertension at 12 to 28 percent.
The study was published online Monday in the Journal of the American College of Cardiology.
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