Snoring

"Snoring" is the term used to describe the sound of obstructed breathing during sleep. Though the noise itself may be comical, snoring is no joke, and can in fact be a serious medical problem. The rattling noise of snoring is caused by vibration of the soft parts of the upper airway. In simple terms, the mouth and throat consist of a bony shell (the vertebrae of the neck, the base of the skull, and the upper and lower jaws), covered on the inside with soft tissues (the muscle of the tongue, and the mucous membrane and muscles that line the back of the mouth and the throat). The hard bony shell of this anatomical region does not change in sleep, but the soft tissues do.

During sleep, the circular muscles at the back of the mouth and the throat relax, and this relaxation allows these soft tissues to be so flaccid that they can vibrate when air passes them. The vibration of these loose soft tissues causes the snoring sound, with its characteristic rumble. There are several different soft-tissue structures that can vibrate in sleep. The tongue, simply a large thick mass of muscle, is attached to the floor of the mouth and the front part of the pharynx. During sleep, when the muscles in this area relax (as is common in deep sleep), the tongue, because of its weight, may passively fall toward the back of the throat. This is more likely to happen if you are lying flat on your back. The movement of the tongue backward may narrow the airway. Structures at the top of the mouth can also contribute to snoring. Toward the front of the mouth, the roof consists of hard bone - the bony palate - covered with mucous membrane. However, the back third of the roof of the mouth consists only of muscle -the soft (that is, with no bone beneath it) palate. If you open your mouth and look in a mirror, you will see at the back of the roof of your mouth a fold of tissue hanging down in the midline. This is called the uvula, from the Latin uva, meaning grape, because early anatomists thought it resembled a small grape hanging down from the soft palate. The uvula functions to direct food away from the space behind the nose and down to the esophagus below. However, during sleep, this whole area of the muscles of the soft palate, including the grape-like uvula, becomes quite relaxed and sags, obstructing the flow of air. On either side of the uvula lie the tonsils, and below this the pharynx itself, which consists of circular muscle, much like that in the soft palate. All these tissues can relax during deep sleep, and this relaxation, this sagging, has the effect of narrowing the opening through which air must pass. Anything that causes the airway to narrow can cause the sound of noisy, obstructed breathing. In sleep, breathing is regulated through brain centers that initiate respiration by sending a stimulus to the muscle of the diaphragm. This stimulus causes the diaphragm to begin to move; this is the first mechanical step involved in moving air into the chest. As the diaphragm begins to move down, it creates a negative pressure within the lungs themselves, as occurs in opening a bellows. This creation of the negative pressure inside the chest cavity causes air to flow from outside the body through the tubing of the airways, and into the lungs. It's important to understand that this occurs because the movement of the diaphragm, and to a lesser extent the chest wall itself, has created a pressure difference between the air on the outside of the body and the air inside the chest. If there is any obstruction to this air flow (such as that mentioned above), then, as the air does move, it causes vibration of these tissues, and the resulting sound we know as snoring.

In general, about 20 percent of the adult population snore regularly, with men snoring more than women, and older people snoring more than young people. At age thirty-five, only 20 percent of men and 5 percent of women snore. By age sixty though, a full 60 percent of men and almost 40 percent of women snore. Snoring is three times more common in people who are overweight than in thin people, and is rated as a serious problem in almost one-third of marriages.

Causes Of Snoring

Anything that causes narrowing of the tubing of the upper airway, or excessive laxity of the tissues that line the airway, causes the air moving past to vibrate, and this vibration of the moving air produces the sound we recognize as snoring. Common causes for snoring include the following:

• Anything that decreases the tone in the muscles of the upper airway will cause these muscles to be softer, less rigid, and more easily able to vibrate in the moving air. Alcohol is a common offender here, but so are antihistamines, sleeping pills, and many other medicines or chemicals that have a sedative or relaxing effect on these tissues.
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• Anything that causes narrowing of the airway anatomically will cause turbulence of the air flowing by, resulting in snoring. In the nose (for in sleep, air is moved through both the mouth and the nose), anatomical obstruction such as nasal polyps, old injuries, and old fractures means that the diameter of the tubing through which the air moves is both smaller and irregular. Similarly, swelling of the mucous membranes of the nose (such as might result from allergy or congestion due to a cold) also causes narrowing of the tubing. In the mouth, a large tongue, a short thick neck, or even a receding chin can result in a narrowing of the airway when the muscle support for the tongue is relaxed during deep sleep. On the roof of the mouth, an excessively long soft palate may cause snoring.
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• Obesity causes narrowing of the airway because fat deposits that occur below the mucous membrane of the back of the pharynx produce effective narrowing as well. Hypothyroidism (underactive thyroid) causes the same sort of thickening below this mucous-membrane layer, with the same tendency toward snoring.
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• Any reason for increased amounts of deep sleep will cause increased time for snoring. If you are overtired, chances are you will spend more of the night in deep sleep and, as a result, your chances of snoring are greater.
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• In children, snoring is almost always caused by obstruction to air flow because of enlargement of the tissues of the upper airway. Nasal congestion resulting from allergies or infections (such as colds) is a common cause of snoring. Because the upper airway in children is much smaller than it is in adults, a small amount of congestion or secretion can cause significant snoring. At the back of the throat, snoring is commonly caused by adenoid or tonsil enlargment in children.