- TUESDAY, July 22 (HealthDay News) — A study links night-time
heart attacks with the breathing disorder sleep apnea, which makes people
gasp for breath every few minutes.

The link is not fully established, but it seems logical, said Dr.
Virend Somers, a cardiologist from the Mayo Clinic who is lead author of
the report in the July 29 issue of the Journal of the American College
of Cardiology.

Most heart attacks occur in the day, generally between 6 a.m. and noon,
Somers said. Having one during the night, when the heart should be most at
rest, means that something unusual happened, he said. Somers and his
colleagues have been working for a decade to show that sleep apnea is to
blame.

Their studies have looked at the most common form, obstructive sleep
apnea, in which the tube carrying air to the lungs, collapses
periodically, blocking the flow. “About 10 years ago, we showed that
obstructive sleep apnea has a powerful effect on the sympathetic nervous
system, causing an acute increase in adrenaline flow, high blood pressure
and lack of oxygen,” Somers said.

That study was followed by another showing that sudden death at night
is more common for people with sleep apnea. An obvious cause of sudden
death is a heart attack, so in this latest study, Somers and his
colleagues studied the breathing patterns of 92 people admitted to the
hospital after heart attacks.

“For those who had heart attacks at night, the vast majority had
undiagnosed sleep apnea,” Somers said. “So, perhaps sleep apnea is acting
as a trigger for night-time heart attacks.”

The “perhaps” is there because it is an observational study, not the
kind of carefully controlled study that is the gold standard of medical
research. Prospects for such a study, in which people with and without
sleep apnea would be followed for months or years to determine their risk
of night-time heart attacks, are dim, Somers acknowledged.

Several studies have shown a link between sleep apnea and cardiac
problems, said Dr. Allan Pack, director of the sleep center at the
University of Pennsylvania. The largest, done several years ago, followed
thousands of individuals. “It showed that people with sleep apnea who
refused treatment had a three- to fourfold increased risk of cardiac
events,” Pack said.

What the new study adds is “a relative difference in the timing of
cardiac events,” he said. In clinical practice, if someone has a heart
attack in the night, “you would strongly suspect sleep apnea,” Pack
said.

If tests detect sleep apnea, there is an effective treatment available
that can reduce the risk of future cardiac events, he said. Continuous
positive air pressure (CPAP) keeps airways open continuously by pushing
air into the lungs through a face mask.

“It might be cumbersome, but it is effective,” Pack said.

More information

Learn about the symptoms and treatment of sleep apnea from the American Sleep Apnea
Association.