Sleep Apnea Connection to Stroke and Death Explained
by New Study
One in 10 senior citizens suffer with sleep apnea
that is more common as people age
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. It may help explain
whey people with sleep apnea – many of them senior citizens – are more
likely to suffer strokes and to die in their sleep.
Sleep apnea is the most commonly diagnosed
condition among sleep-related breathing disorders and can lead to
debilitating and sometimes fatal consequences for the estimated 18
million Americans who have been diagnosed with the disorder.
It is estimated that one in ten senior citizens
have sleep apnea, which becomes more common as people age.
The aging process limits the ability of brain
signals to keep your throat muscles stiff during sleep. This makes it
more likely that the airway will narrow or collapse, according to the
National Heart, Lung and Blood Institute.
This study identifies the mechanism behind stroke
in these patients.
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.
More About Sleep Apnea
Also
called: Sleep-disordered breathing
Sleep apnea is a common disorder that can be serious. In
sleep apnea, your breathing stops or gets very shallow. Each pause in
breathing typically lasts 10 to 20 seconds or more. These pauses can
occur 20 to 30 times or more an hour.
The most common type is obstructive sleep apnea. That
means you are unable to get enough air through your mouth and nose into
your lungs. When that happens, the amount of oxygen in your blood may
drop. Normal breaths resume with a snort or choking sound. People with
sleep apnea often snore loudly. However, not everyone who snores has
sleep apnea.
When your sleep is interrupted throughout the night, you
can be drowsy during the day. People with sleep apnea are at higher risk
for car crashes, work-related accidents and other medical problems. If
you have it, it is important to get treatment.
More from
National Heart, Lung, and Blood Institute below news report
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 published by The American Physiological Society.
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
● air pressurization mask or CPAP
● nasal inserts
● dental appliances
● weight reduction for the obese
In some cases, surgery may be advised.
Background Information
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.
Who Is At Risk for Sleep Apnea?
It's estimated that more than 12 million American
adults have obstructive sleep apnea. More than half of the people who
have this condition are
overweight.
Sleep apnea is more common in men. One out of 25
middle-aged men and 1 out of 50 middle-aged women have sleep apnea.
Sleep apnea becomes more common as you get older.
At least 1 out of 10 people over the age of 65 has sleep apnea. Women
are much more likely to develop sleep apnea after menopause.
African Americans, Hispanics, and Pacific Islanders
are more likely to develop sleep apnea than Caucasians.
If someone in your family has sleep apnea, you're
more likely to develop it.
People who have small airways in their noses,
throats, or mouths also are more likely to have sleep apnea. Smaller
airways may be due to the shape of these structures or allergies or
other medical conditions that cause congestion in these areas.
What Causes Sleep Apnea?
When you're awake, throat muscles help keep your
airway stiff and open so air can flow into your lungs. When you sleep,
these muscles are more relaxed. Normally, the relaxed throat muscles
don't stop your airway from staying open to allow air into your lungs.
But if you have obstructive sleep apnea, your
airways can be blocked or narrowed during sleep because:
● Your throat muscles and tongue relax more than
normal.
● Your tongue and tonsils (tissue masses in the
back of your mouth) are large compared to the opening into your
windpipe.
● You're
overweight. The extra soft fat tissue can thicken the wall of the
windpipe. This causes the inside opening to narrow and makes it harder
to keep open.
● The shape of your head and neck (bony
structure) may cause a smaller airway size in the mouth and throat area.
● The aging process limits the ability of brain
signals to keep your throat muscles stiff during sleep. This makes it
more likely that the airway will narrow or collapse.
Not enough air flows into your lungs when your
airways are fully or partly blocked during sleep. This can cause loud
snoring and a drop in your blood oxygen levels.
When the oxygen drops to dangerous levels, it
triggers your brain to disturb your sleep. This helps tighten the upper
airway muscles and open your windpipe. Normal breaths then start again,
often with a loud snort or choking sound.
The frequent drops in oxygen levels and reduced
sleep quality trigger the release of stress hormones. These compounds
raise your heart rate and increase your risk for
high blood pressure,
heart attack, stroke, and
irregular heartbeats. The hormones also raise the risk for or worsen
heart failure.
Untreated sleep apnea also can lead to changes in
how your body uses energy. These changes increase your risk for
obesity and diabetes.
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. It may help explain
whey people with sleep apnea – many of them senior citizens – are more
likely to suffer strokes and to die in their sleep.
Particularly when it occurs with elevated nighttime
blood pressure; sleep patterns should be checked for those with high
blood pressure
