People who are less sensitive to pain may be at
increased risk of having a "silent" heart attack, a
new study hints. Chest pain is one of the "classic"
symptoms of a heart attack. But many people have
so-called silent heart attacks, where they notice no
obvious symptoms. "Almost everyone knows what a
heart attack is. When we hear about it, we think of
chest pain and emergency medical care," the lead
researcher said on the new study. "But what's less
known is, many people experience heart attacks
without knowing it -- without ever receiving a
diagnosis," researcher added. No one knows why that
is. But the new findings suggest that pain tolerance
might be a factor. Using a standard test of pain
sensitivity, research team found that people who had
a silent heart attack in the past generally had a
higher pain tolerance than people who'd sought
treatment for heart attack symptoms. When the
researchers dug deeper, the connection appeared to
be stronger in women than men. One study visit
involved a standard pain-sensitivity test where
people plunge a hand into cold water for as long as
they can stand it, for up to two minutes. At the
next study visit, participants underwent
electrocardiograms -- which can detect signs of a
past heart attack, even if it was unrecognized at
the time. Of over 4,800 adults who had both tests,
it turned out that 8 percent had previously had a
silent heart attack. Just under 5 percent had ever
had a diagnosed heart attack. When the researchers
compared the two groups, they found that people who
had a silent attack had, on average, greater pain
tolerance. It's possible that people who tolerate
cold-induced pain are also less sensitive to pain
caused by reduced blood flow to the heart, she said.
There were differences between men and women in the
study. Overall, more men had suffered a heart attack
-- 19 percent versus 7 percent of women. But silent
attacks accounted for three-quarters of all heart
attacks among women, compared with 58 percent among
men. According to research team, that's in line with
past studies: Women are more likely than men to have
atypical heart attack symptoms, and their heart
attacks are more likely to go undiagnosed. It's not
clear how pain sensitivity fits into that picture.
In this study, women generally had less pain
tolerance than men. But the connection between
greater pain tolerance and silent heart attack was
stronger among women than in men. It's possible, she
said, that women with diagnosed heart attacks have
particularly severe symptoms. "It may be that it
'takes more' symptoms to have your heart attack
recognized if you are a woman," she speculated. The
bottom line, according to researcher, is that it's
important for doctors to be on the lookout for
less-obvious heart attack symptoms, especially in
women. "Absence of chest pain should not lower
doctors' alertness toward heart disease," she said.
Sometimes the red flags pop up in the longer term,
she noted. Breathing problems and swelling in the
legs, for instance, can be signs of heart muscle
damage from a previous, undiagnosed heart attack,
she said. Silent attacks, researcher said, are just
as serious as ones that cause obvious chest pain --
carrying similar risks of death or repeat heart
attack over the long term.
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