Even the minor noise that fills everyday life, from the ring of a cell phone
to the conversation that follows, may have short-term effects on heart function,
a small new study suggests.
In the study of 110 adults equipped with portable heart monitors, researchers
found that people's heart rate tended to climb as their noise exposure increased
- even when the noise remained below 65 decibels. That's about as loud as a
normal conversation or laughter.
There was also a negative impact on people's heart rate "variability" - a
measure of the heart's adaptation to what is going on around you. Greater
variability in the interval between heartbeats is better. When people are
relaxed, the space between heartbeats is usually a bit longer as they exhale,
and shorter as they inhale.
When people are stressed, however, some of that natural variation is lost.
And studies have linked lesser heart rate variability to an increased risk of
So does all of this mean you need to wear earplugs to protect your heart?
Probably not, experts say.
For any one person, the effects of everyday noise on heart function may be
small, said Charlotta Eriksson, a researcher at the Karolinska Institute, in
Stockholm, Sweden. Eriksson was not involved in the study.
But since we are all exposed to noise, even a minor effect on heart health
could be important on the broad "population level," said Eriksson, who has
studied the effects of loud traffic - from roads or airports - on people's blood
pressure and heart function.
Research has consistently found links between loud workplaces and an
increased risk of heart disease, said Dr Wenqi Gan, a researcher at North
Shore-LIJ Health System's Feinstein Institute for Medical Research, in
The evidence is more mixed when it comes to "community noise," like traffic
sounds, said Gan, whose own research has found a connection.
He said the mixed results may be because it's difficult to weed out the
effects of community noise on individuals. You might live in a noisy section of
a big city, but have good, sound-muffling windows, for example.
"And some people are more sensitive to noise than others," Gan said. If noise
affects the heart by stressing people out, he said, then your personal
sensitivity to it would be important.
Fight or flight mode
The new findings are based on 110 adults who wore portable devices that
measured their heart activity and noise exposure during their normal daily
What was "interesting," Eriksson said, is that lower-level noise seemed to
curb activity in the parasympathetic nervous system - the branch of the nervous
system that acts as a "brake," lowering heart rate and relaxing the blood
vessels, for example.
Louder noise, meanwhile, seemed to rev up the sympathetic nervous system -
the branch that boosts heart rate, constricts blood vessels and otherwise sends
us into "fight or flight" mode.
The value of the findings is that they suggest a biological reason for why
noise has been linked to ill heart effects, said Alexandra Schneider, one of the
researchers in the Institute of Epidemiology at Helmholtz Zentrum Munchen, in
Germany, who worked on the study.
"Our main focus was to find a possible mechanism that could be responsible
for the observed health effects in other studies," Schneider said.
The study was not designed to offer people advice on how much noise is "bad"
for their hearts, she said.
Gan agreed. "This study is a first step in exploring the underlying
biological mechanisms for the association between noise exposure and
cardiovascular disease," he said. "We need more studies like this."
A big question, said study author Schneider, is whether the short-term
effects of noise, repeated over time, ultimately affect heart health -
particularly for people who already have chronic medical conditions.
Although the study tied increased noise exposure to a rise in heart rate, it
did not establish a cause-and-effect relationship.
The US Environmental Protection Agency has more information on noise pollution.