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.