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 In two analyses covering four industrialized
countries and more than 5,000 people, researchers also found that
home blood pressure monitoring frequently picks up that so-called
masked hypertension.
If that leads to more people with hidden high blood pressure getting
treatment, it would be affordable and worthwhile to expand home
monitoring, they say.
"We know that a lot of cardiovascular complications occur in people
who are normotensive if you measure the blood pressure in the
regular way in the office," Dr. Jan Staessen told Reuters Health in
an email.
Staessen, a researcher in the Division of Cardiovascular Diseases at
the University of Leuven in Belgium, is senior author of the studies
published in PLOS Medicine and Hypertension.
About 10 percent of the general population has normal or high-normal
blood pressure readings at the doctor's office, but they actually
have high blood pressure at home or at work. This is known as masked
hypertension and it often goes untreated because it's hard for
doctors to detect.
To see how masked hypertension affects risk for cardiovascular
events like heart attack and stroke, Staessen and colleagues
analyzed data from five previous studies of home-monitored blood
pressure done in Finland, Japan, Greece and Uruguay.
For the new study, blood pressure readings with a top number below
120 and a bottom number below 80 were considered "optimal." Normal
blood pressure was a reading of 120-129/80-84, "high-normal" was
130-139/85-89, mild hypertension was 140-159/90-99 and severe
hypertension was a top number of 160 or higher and a bottom number
of 100 or more.
The researchers considered a home reading of 130/85 or above to
indicate masked hypertension when the person did not meet the
criteria for high blood pressure at the doctor's office.
By that standard, they found that 5 percent of those with "optimal"
blood pressure at the clinic, 18.4 percent with "normal" clinic
readings and 30.4 percent with "high-normal" clinic readings had
masked hypertension at home.
During a median 8.3 years of follow-up, participants with masked
hypertension had between 2.24 and 2.65 times the risk for
cardiovascular events when compared to those with true normal blood
pressure.
In a commentary published in PLOS Medicine, Dr. Mark Caulfield of
Barts and The London School of Medicine and Dentistry points out
that cardiovascular disease is the leading cause of death worldwide.
"With a growing burden of high blood pressure and a growing
availability of affordable devices, home blood pressure monitoring
could be used to diagnose high blood pressure and help decide whom
to treat," he writes. "It empowers patients to take on a role in
assessment of their blood pressure." In a separate
analysis, Staessen looked at how home blood pressure monitoring
affected the cardiovascular risk profiles of patients with masked
hypertension or with the opposite problem — so-called white coat
hypertension. That's when patients have high blood pressure readings
at the doctor's office but normal blood pressure at home.
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The study included 6,458 participants, 5,007 of whom were not
being treated for blood pressure problems. Of that untreated group,
404 people had masked hypertension, 695 had white coat hypertension
and 924 had sustained hypertension.
Staessen's team found that masked hypertension raised risk for
cardiovascular events in the untreated group by 55 percent compared
to people with normal blood pressure.
White coat hypertension raised the risk by 42 percent and
sustained hypertension more than doubled it.
Even among the participants who were being treated for high blood
pressure, masked hypertension diagnosed by home monitoring raised
cardiovascular risk by 76 percent.
The patients with masked hypertension were probably undertreated
because of their low office blood pressure, Staessen and his
colleagues write.
Whether people are already on blood pressure treatment or not,
Staessen told Reuters Health, those who have risk factors for masked
hypertension, including smokers, obese people and older people,
should monitor their blood pressure at home.
"The clinical relevance of masked hypertension is that often our
blood pressure assessments are done in the clinic in a sort of an
ideal setting where there's a nurse or a medical assistant and
provider," said Dr. Edgar Miller, III, an epidemiologist at Johns
Hopkins University in Baltimore.
Miller, who was not involved in the studies, said that home
monitoring of blood pressure is becoming popular, but it's not
standard yet, because current treatment guidelines are built around
clinical assessments of blood pressure.
"We need to figure out ways to encourage home blood pressure
monitoring, figure out standardized ways to report it to your
provider, and there's more research needed into how providers should
react to home blood pressure measurements," Miller said.
___
Sources: http://bit.ly/1dQCAAl
and http://bit.ly/1dR40fr
PLOS Medicine, online Jan. 21, 2014;
http://bit.ly/1iPEqth
Hypertension, online Jan. 13, 2014.
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