Snoring
Medical Author: Andrew Verneuil, MD
Medical Editor: Jay W. Marks, MD
What is snoring?
Snoring, like all other sounds, is caused by vibrations that cause particles
in the air to form sound waves. For example, when we speak, our vocal cords
vibrate to form our voice. When our stomachs growl (borborygmus), our
stomach and intestines vibrate as air and food move through them. While we are
asleep, turbulent air flow can cause the tissues of the nose and throat
to vibrate and give rise to snoring. Essentially, snoring is a sound
resulting from turbulent airflow that causes tissues to vibrate during
sleep.
What causes snoring?
While we are breathing, air flows in and out in a steady
stream from our nose or mouth to our lungs. There are relatively few sounds when we are
sitting and breathing quietly. When we exercise, the air moves more quickly
and produces some sounds as we breathe. When we are asleep, the area at the
back of the throat sometimes narrows. The same amount of air passing through
this smaller opening can cause the tissues surrounding the opening to
vibrate, which in turn can cause the sounds of snoring. Different people who
snore may have various reasons for the narrowing of the area at the back of
the throat. The narrowing can be in the nose, mouth, or throat.
Any person can snore. Frequently, people who do not
regularly snore will report snoring after a viral illness, after drinking
alcohol, or when taking
some medications. Studies estimate that 45 % of men and 30% of women snore
on a regular basis. People who snore can have any body type. We
frequently think of a large man with a thick neck as a snorer. However, a thin woman
with a small neck can snore just as loudly. In general, as people get older
and as they gain weight, snoring will worsen.
Normal breathing
For breathing at rest, it is ideal to breathe through the
nose. The nose acts as a humidifier, heater, and filter for the incoming air.
When we breathe through our mouth, these modifications to the air entering our
lungs do not occur. Our lungs are still able to use the cold, dry, dirty air, but
you may have noticed that breathing really cold, dry, or dirty air can be
uncomfortable. Therefore, our bodies naturally want to breathe through the
nose if possible.
The nose is made up of two parallel passages, one on each side. They are
separated by the septum, which is a relatively flat wall of cartilage, bone, and lining tissue
called the nasal mucosa. On the lateral
side of each passage, there are three nasal turbinates, which are long,
cylindrical-shaped structures that lie roughly parallel to the floor of the
nose. The turbinates contain many small blood vessels
that function to regulate airflow. If the blood vessels in the turbinates
increase in size, the turbinate as a whole swells, and the flow of air
decreases. If the vessels narrow, the turbinates become smaller and airflow
increases. Everyone has a natural nasal cycle that generally will shift the
side that is doing most of the breathing about every eight hours. For
example, if the right nasal turbinates are swollen, most of the air enters
the left nasal passage. After about eight hours, the right nasal turbinates
will become smaller, and the left nasal turbinates will swell, shifting the
majority of breathing to the right nasal passage. You may notice this cycle
when you have a cold or if you have a chronically stuffy nose. The
turbinates may also swell from allergic reactions or external stimuli, such
as cold air or dirt.
Mouth breathing and snoring
As discussed above, we naturally want to breathe through
our noses. Some people cannot breathe through their noses because of obstruction
of the
nasal passages. This can be caused by a deviation of the septum, allergies,
sinus infections, swelling of the turbinates, or large adenoids. In adults,
the most common causes of obstruction are septal deviations from a broken
nose or tissue swelling from allergies. In children, enlarged adenoids are
often the cause of the obstruction. People with nasal airway obstruction who
must breathe through their mouths are therefore sometimes called “mouth
breathers.” Many mouth breathers snore, because the flow of air through the
mouth causes greater vibration of tissues.
The soft palate and snoring
The soft
palate is a muscular extension of the bony roof of the mouth (hard
palate). It separates the back of the mouth (oropharynx) from the nasal
passages (nasopharynx). It is shaped like a sheet attached at three sides
and hanging freely in the back of the mouth. This is important when
breathing and swallowing. During nasal breathing, the palate moves forward
and “opens” the nasal airway for air. During swallowing, the palate moves
backward and “closes” the nasal passages, thereby directing the food and
liquid down the esophagus instead of into the back of the nose. The uvula is
the middle extension of the palate. It assists with the function of the soft
palate and also is used in some languages (Hebrew and Farsi) to produce the
guttural fricative sounds (like in the Hebrew word “L'chaim”). English words
do not use the guttural fricative sounds. The palate and uvula often are the
structures that vibrate during snoring and surgical treatments for snoring
alter these structures and prevent guttural fricative sounds. Therefore, if
you speak a language that uses guttural fricative sounds, make sure you do
not have a surgical procedure to improve snoring.
The narrowed airway and snoring
The tonsils are designed to
detect and fight infections. They are located at the back of the mouth on each
side of the throat (oropharynx). Like other infection-fighting tissue, the
tonsils swell while they are fighting bacteria and viruses. Often, the tonsils
do not return to their starting size after the infection is gone. They can remain enlarged (hypertrophied)
and can narrow the airway, vibrate, and cause snoring.
The soft palate, as described above, is the flap of tissue that hangs down
in the back of the mouth. If it is too long or floppy, it can vibrate and
cause snoring. The uvula is suspended from the center of the palate. An
abnormally long or thick uvula also can contribute to snoring.
The base of the tongue is the part of the tongue that is
the farthest back in the mouth. The tongue is a large muscle that is important
for directing food while chewing and swallowing. It also is important for
shaping words while we are speaking. It is attached to the inner part of the jaw
bone
(mandible) in the front and to the hyoid bone underneath. The tongue must be
free to move in all directions to function properly. Therefore, it is not
attached very tightly at the tip or top of the tongue. If the back of the
tongue is large or if the tongue is able to slip backwards, it can narrow
the space through which air flows in the pharynx, which can lead to
vibrations and snoring.
Stage of sleep and snoring
Snoring can occur during all or only some stages of
sleep. Snoring is most common in rapid eye movement (REM) sleep, because of the loss of muscle tone
characteristic of this stage of sleep. As discussed in the article on sleep
stages, during REM sleep, the brain sends the signal to all the muscles of
the body (except the breathing muscles) to relax. Unfortunately, the tongue,
palate, and throat can collapse when their muscles relax. This can cause the
airway to narrow and worsen snoring.
Sleeping position and snoring
When we are asleep, we are usually (though not always)
lying down. Gravity acts to pull on all the tissues of the body, but the tissues
of the pharynx are relatively soft and floppy. Therefore, when we lie on our
backs, gravity pulls the palate, tonsils, and tongue backwards. This often
narrows the airway enough to cause turbulence in airflow, tissue vibration and
snoring. Frequently, if the snorer is gently reminded (with an elbow to the ribs) to
roll onto his or her side, the tissues are no longer pulled backwards and
the snoring lessens.
Medications and alcohol and snoring
The root cause of snoring is vibration of the tissues while breathing. Some
medications as well as alcohol can lead to enhanced relaxation during sleep.
As the muscles of the palate, tongue, neck, and pharynx relax more, the
airway collapses more. This leads to a smaller airway and greater tissue
vibration. Some medications encourage a deeper level of sleep, which also
can worsen snoring.
Next: Why is snoring a problem? »
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