Sound Asleep Snoring

Q: Why do people only snore when they are asleep? You breathe all the time, but it's noisier when you are fast asleep. Why?
Hank, Boise, Idaho, USA

A: We almost cannot snore while we're awake, because we cannot relax critical muscles enough to snore. For normal adults, that extreme decrease in muscle activity only happens in the deeper stages of sleep. When awake, muscles keep even the most constricted part of the passage open enough, for air to quietly scoot down.

Airways are narrowest around the roof of our mouths (the soft palate), the back of our tongue and along the air passage at the back of the mouth (the oropharynx). See figure.

From time to time, about 45% of us snore. Then, as we sink into deeper sleep and our bodies relax totally, the passageways partly close and we snore. Inhaling, we not only suck in air but also tend to suck the soft parts of the passageway together and restrict the airway. The muscles surrounding these soft areas (the soft palate, the back tongue and the oropharynx) tighten to prevent airway collapse, but can't contract enough to keep the passage wide open and air flowing freely. Restricted airflow vibrates sagging soft tissues. Fluttering tissues produce a snore, somewhat like a bagpipe's vibrating reed drones its tune.

About 25% of us snore habitually. But there is one sure cure for snoring — eliminate gravity's effects. "Free falling in orbit, we do not snore, as there is no gravity to pull on the soft tissues," emails pulmonary physiologist Kim Prisk professor at the University of California at San Diego.

My wife says I make a noise like a stranded whale. — Rex Hunt

Further Reading:

Snoring: analysis, measurement, clinical implications and applications by F. Dalmasso, R Prota, European Respiratory Journal, 1996, 9, 146-159.

Snoring, bupa.com

The effects of snoring, The Franklin Institute

Readers' answers to question of the month:

People snore when sleeping, because the muscles in your tongue,throat and mouth relax, causing throat tissues to sag. As you breathe, these sagging tissues narrow your airway, and vibrate or flutter, causing the sound of snoring. The narrower the airway, the greater the sound of snoring.
Neelie, Sutton-in-ashfield, England

When people sleep, their muscles relax, including those at the back of the throat. This relaxing causes the soft tissue at the back of the throat to vibrate when they breathe. We call it snoring.
Mary Lou, North Bay, Ontario, Canada

It is the only way to annoy others, while you sleep. While awake, you can annoy others in a wide variety of behaviors.
Kenneth, Centennial, Colorado, USA

Next month's question:
Recently we were sitting outside and heard a bizarre noise coming from something flying over our heads. We realized it was a couple of swans. Now we are trying to figure out what the noise was. Some of us suggested it was a sort of singing or signaling, others that it was their wings making the noise. Can you help us out? We have a dinner at stake!
Mimi, Copenhagen, Denmark

I'll publish the best answers, and you get credit. Click here Answer-the-question to give me your answer.

(Answered June 11, 2007)