FOR IMMEDIATE RELEASE
January 6, 2009
Contact: Donna Krupa
Office: (301) 634-7253
commoff@the-aps.org
Study Helps Explain
Connection Between Sleep Apnea, Stroke And Death
Researcher offers tips to watch for in identifying risks
BETHESDA, Md. (Jan. 6, 2009)
− Obstructive sleep apnea decreases blood flow to the brain,
elevates blood pressure within the brain and eventually harms the brain’s
ability to modulate these changes and prevent damage to itself, according to
a new study published by The American Physiological Society. The
findings may help explain why people with sleep apnea are more likely to
suffer strokes and to die in their sleep.
Sleep apnea is the most commonly diagnosed condition
amongst sleep-related breathing disorders and can lead to debilitating and
sometimes fatal consequences for the 18 million Americans who have been
diagnosed with the disorder. This study identifies a mechanism behind stroke
in these patients.
The study, “Impaired cerebral autoregulation in
obstructive sleep apnea” was carried out by Fred Urbano, Francoise Roux,
Joseph Schindler and Vahid Mohsenin, all of the Yale University School of
Medicine in New Haven, Connecticut. It appears in the current issue of the
Journal of Applied Physiology.
During sleep apnea episodes, the upper airway becomes
blocked, hindering or stopping breathing and causing blood oxygen levels to
drop and blood pressure to rise. The person eventually awakens and begins
breathing, restoring normal blood oxygen and blood flow to the brain.
Ordinarily, the brain regulates its blood flow to meet
its own metabolic needs, even in the face of changes in blood pressure -- a
process known as cerebral autoregulation. This study found that the repeated
surges and drops in blood pressure and blood flow during numerous apnea
episodes each night reduces the brain’s ability to regulate these functions.
Condition a health risk
Up to 4% of the population suffers from obstructive
sleep apnea. In a previous study, Dr. Mohsenin and his colleagues showed
that people with sleep apnea are three times more likely to suffer a stroke
or die, compared to people in a similar state of health but without sleep
apnea.
“After we found that sleep apnea is a risk factor for
stroke and death, independent of other risk factors, we hypothesized that
there must be something wrong with the regulation of blood flow to the
brain,” Dr. Mohsenin said. Participants included people with severe sleep
apnea who experienced more than 30 apneas an hour during sleep time. The
participants were about 47 years old, were free of cardiac disease and had
not experienced any strokes. The study also included a control group which
did not have sleep apnea but was similar in most other ways.
The researchers monitored the participants’ blood
pressure while standing and squatting. Standing from a squatting position
lowers blood pressure as can be experienced during normal daily activity.
They also monitored the participants as they slept. The study found that the
sleep apnea group:
-
had lower cerebral blood flow velocity
-
had significantly lower blood oxygen levels during sleep
-
took longer to recover from a drop in blood pressure
-
took longer to normalize blood flow to the brain
Identification is key
Overall, the findings indicate that repeated surges and
drops in blood pressure and low oxygen levels eventually impair the body’s
ability to regulate blood flow to the brain. Sleep apnea may occur over a
long period of time before the person becomes aware of it and seeks medical
treatment. Here are the symptoms Dr. Mohsenin says to watch out for:
-
After eight hours of sleep, you don’t feel rested. During
the day, you feel more and more tired, and by afternoon, you want to
nap.
-
You experience loud, habitual snoring that disturbs
others.
-
Your bed partner observes pauses in your breathing.
The treatment of obstructive sleep apnea with an airway
pressurization mask has been shown to normalize cerebral autoregulation,
although there are not yet any studies to show that it reduces the rate of
stroke. Those who are being treated for sleep apnea should remain compliant
with treatments, according to Dr. Mohsenin, including use of
In some cases, surgery may be advised.
NOTE TO EDITORS: To interview Dr. Mohsenin,
please contact Donna Krupa at (301) 634-7253 or at
commoff@the-aps.org.
Funding: Yale University, Department of Medicine
and Yale Center for Sleep Medicine
***
Physiology
is the study of how molecules, cells, tissues and organs function to create
health or disease. The American Physiological Society (www.The-APS.org/press)
has been an integral part of this discovery process since it was established
in 1887.
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