Siamak T. Nabili, MD, MPH
Siamak T. Nabili, MD, MPH
Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.
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 stomach growls (borborygmus), our stomach and intestines vibrate as air and food move through them.
While we are asleep, turbulent airflow 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.
How common is snoring?
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Any person can snore. Studies estimate that 45% of men and 30% of women snore on a regular basis. Frequently, people who do not regularly snore will report snoring after a viral illness, after drinking alcohol, or when taking some medications.
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.
What causes snoring?
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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. This happens because air is moving in and out of the nose and mouth more quickly and this results in more turbulence to the airflow and some vibration of the tissues in the nose and mouth.
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 have different reasons for the narrowing. The narrowing can be in the nose, mouth, or throat.
The function of the nose in 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 occur to a lesser extent. Our lungs are still able to use the colder, drier, dirtier 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, called the nasal cavity. They are separated by a thin wall in the middle (the septum), which is a relatively flat wall of cartilage, bone, and lining tissue (called the nasal mucosa). On the lateral side (the wall of the nose closer to the cheeks) 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 (long standing) 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 nasal septum, allergies, sinus infections, swelling of the turbinates, or large adenoids (tonsils in the back of the throat).
In adults, the most common causes of nasal obstruction are septal deviations from a broken nose or tissue swelling from allergies.
In children, enlarged adenoids (tonsils in the back of the throat) 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.
The soft palate is important when breathing and swallowing.
The uvula is the small extension at the back of the soft 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 attached uvula often are the structures that vibrate during snoring and surgical treatments for snoring may alter these structures and prevent guttural fricative sounds. Therefore, if you speak a language that uses guttural fricative sounds, a surgical treatment for snoring may not be recommended or appropriate for you.
Narrowed airways 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). They are also called the palatine tonsils. Like other infection-fighting tissue, the tonsils swell while they are fighting bacteria and viruses. Often, the tonsils do not return to their normal 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 and back of the soft 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
Sleep consists of several stages, but in general they can be divided into REM (rapid eye movement) and non-REM stages. Snoring can occur during all or only some stages of sleep. Snoring is most common in REM sleep, because of the loss of muscle tone characteristic of this stage of sleep.
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 they 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 (for example, with a gentle thrust of the elbow to the ribs or a tickle) to roll onto his or her side, the tissues are no longer pulled backwards and the snoring lessens.
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