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 Researchers found that self-measurement at home with wrist devices
often led to false reports of elevated blood pressure when compared
to measurements in a doctor’s office. Accurate readings often
depended on correct positioning of the wrist, which patients either
didn’t understand or didn’t remember how to do.
“Arterial blood pressure is a silent killer,” said lead author Dr.
Edoardo Casiglia, a European clinical hypertension specialist at the
University of Padua in Italy. “It’s important for those with high
blood pressure to be aware of their numbers and receive adequate
treatment.”
High blood pressure, also known as hypertension, can lead to heart
attack, stroke and kidney problems. About one in three adults in the
U.S., or 70 million people, have high blood pressure, according to
the Centers for Disease Control and Prevention.
The American Heart Association recommends that people with high
blood pressure take measurements at home with commercially available
monitoring devices because blood pressure fluctuates throughout the
day and occasional readings at a doctor’s office don’t provide a
true assessment of a person’s condition.
“The only way to monitor blood pressure consistently is to trust
patients to measure at home,” Casiglia told Reuters Health by email.
“Many devices are available, reliable and good. Recently, many wrist
devices have appeared on the market, but they require the wrist to
be placed exactly at heart level.”
Often, as seen in the study, patients rest the wrist device below
heart level, which gives false high numbers and may encourage a
doctor to increase medication. On the other hand, Casiglia said,
holding the wrist at higher than heart level gives false low numbers
and may encourage doctors to reduce treatment.
Casiglia and colleagues trained 720 patients to use wrist devices
and then measured blood pressure at home and in the doctor’s office
with both an upper-arm device and a wrist device. The patients were
instructed to take upper arm and wrist measurements themselves at
home every morning and evening at the same time of day for seven
consecutive days.
In general, healthy people have a systolic blood pressure, the
measurement when the heart beats, of less than 120 mmHg, and
diastolic pressure, when the heart rests, of less than 80 mmHg.
Blood pressures above 140 mmHg systolic or 90 mmHg diastolic are
considered hypertension.
In the current study, a total of 620 patients had inaccurate
measurements at home, with 433 of these having discrepancies of more
than 10 mm/Hg.
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“Even after a training course, we found that choosing correct wrist
position largely depends on cognitive pattern, which can be
influenced by age and education,” Casiglia said. “This is why the
wrist devices are not good for everybody.”
Doctors should decide which patients are a good fit for at-home
wrist measurement, the study team writes in Hypertension.
“Using upper arm measurement is the gold standard and always our
first choice,” said Dr. Vincent Canzanello, a clinical hypertension
specialist at the Mayo Clinic in Rochester, Minnesota, who wasn’t
involved with the study. “However, sometimes the cuffs don’t fit
larger arms or are painful for patients.”
One limitation of the study is a potential “white coat effect,” in
which some people’s blood pressure rises simply from the stress of
being in a doctor’s office, Canzanello told Reuters Health.
“Typically, our clinical assistants do several automated readings
before a health care provider ever enters the room to avoid this
effect,” he said. “Studies show that physicians are notoriously bad
at measuring blood pressure in terms of following the proper
guidelines,” he added.
About a third of Americans with high blood pressure have it
controlled correctly, according to the American Heart Association.
Proper at-home measurement could help patients obtain the correct
treatment and medication.
“A device that measures the upper arm with the appropriately-sized
cuff is the best option,” Canzanello said. “But for those who need
to use a wrist device, this study shows that taking measurements
with the proper instructions is key.”
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