Summer of Science: Why don't snorers wake themselves up

Ask any snorer why their sonorous rumblings don't wake them up and they will almost inevitably give the same, simple response: "Why ask me? I don't snore!"

A snorer's blissful ignorance of their own snuffles gives the impression they must sleep soundly through them, while the rest of the household listens on in frustration or horror.

But just because they don't remember waking up, doesn't mean they sleep like a baby. To explain why, we need to look at why some of us snore in the first place. Let's break it down.

Your mouth and throat are full of all sorts of delightfully soft, floppy bits, such as your uvula, tonsils, adenoids and other bits of tissue.

When you're awake, your body actively holds all these bits in their designated positions, ready for action.

But when you fall asleep, your muscles relax and everything is free to loosen up.

This relaxation is an important part of sleeping. As well as allowing our bodies to rest and recuperate, partial muscle paralysis prevents us from acting out our dreams while not fully conscious and walking.

While a live action mime of our dreams could be an amusing insight to spectators, it could also be dangerous to us - and them.

As well as keeping your limbs safely tucked in bed, sleep relaxation affects the muscles that hold everything in place.

For some people (but certainly not any of us), this relaxation is enough for the soft tissues in our mouths to flop into undesirable positions and partially block the flow of air as they breathe.

Snoring is the resulting sound of all the oral smooshy bits vibrating and slapping together as air forces its way through the obstruction when we breathe.

Those mouth parts that cause all the trouble are actually the result of human evolution.

If we were designing a perfect anti-snoring airway, it would be a long, straight tube with no soft parts at all. Unfortunately, a lot more is required of our airways than just unlaboured breathing.

In order to vocalise beyond simple grunts, faces and throats have been reshaped to accommodate more sophisticated sound apparatus - most of which is soft tissue.

Our tongues have migrated further back in our throats to shape different sounds.

Compared to other mammals, our tongue rests precariously close to the back of our upper airway - the perfect place to become a blockage when we snooze.

Our upright posture has also had an effect, shifting throats directly underneath skulls and leaving less room in which to fit all the additional squishy bits - prime conditions for the airway obstruction that leads to snoring.

A loud crash from the kitchen in the middle of the night is almost certain to wake us up.

Whether tree crash or pet adventure, human bodies react to the sound by snapping speedily into a state of awareness.

This is because our ears are still taking in sound while we're asleep, and our brain is still processing - but its decision-making processes are very different to when we're awake. Brains prioritise restfulness while we sleep, filtering out low-priority sounds and letting us snooze through unimportant background noise.

Only high-priority signals trigger wakefulness: research has shown we're more likely to respond to unusual sounds, especially loud sounds that could signal danger, and someone speaking our own names.

For the offending snorer, the brain interprets soft snores as innocuous background noise that needs no further attention.

But what about the ones that rattle the roof shingles?

In fact, very loud snores actually do wake the snorer, but only briefly. We usually need to be in a very deep sleep state for our muscles to be relaxed enough for snoring to start, and at that point our brains are shutting out all but the most important information.

Even if a snore is thunderous enough to make it through this filter, the snorer slips right back to sleep within a matter of seconds.

Brainwave research suggests we can have up to 25 of these "microarousals" per hour without even noticing.

Unfortunately for everyone else in the household, you have to reach that deep sleep state before the snoring starts in order to be able to filter it out.

So bad news for the 'chainsnorers' out there -your wake-ups might be impeding a sustained good night's rest.

For the rest of us, a couple of choices: learn to love the bear, or invest in a comfy pair of earplugs. Sleep tight!

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