"Listen to him, he's out for the count." Most of us have said something like it, or heard it said. Loud snoring sounds like the deepest, most contented sleep imaginable, and the snorer often insists they slept like a log.
The belief is half right, which is why it survives. Heavy snoring does tend to peak during deep sleep. But snoring happens in lighter sleep too, it can break sleep up in ways the snorer never notices, and regular snorers are sleepier during the day than people who do not snore.
Here is what overnight sleep studies show about where snoring happens in the night, and why a loud snorer can wake up feeling as though they have barely slept.
Where the Idea Comes From
The myth rests on everyday observation. The noise usually starts once someone has properly dropped off rather than while they are dozing, and a person snoring away can seem impossible to disturb.
There is a basis for the first part. Snoring needs the muscles that hold the throat open to relax, and that happens when we fall asleep. So a person who is snoring is asleep, and their airway muscles have let go.
Where the reasoning goes wrong is the next step: the assumption that snoring is therefore a sign of good, deep, restorative sleep. Being asleep and sleeping well are not the same thing, and the research separates them quite clearly.
A Quick Guide to the Stages of Sleep
Sleep is not one state. Through the night you cycle through several stages, which sleep studies tell apart using brain waves, eye movements and muscle activity.
Stage N1. The light, drifting transition between waking and sleep.
Stage N2. Established light sleep, a step deeper than N1.
Stage N3, or slow-wave sleep. What most people mean by deep sleep, named after the slow brain waves that mark it. Older research split it into stages 3 and 4, which is why "stage 4" appears in some of the studies.
REM sleep. Rapid eye movement sleep, the stage most associated with dreaming.
When people say a snorer is in deep sleep, they mean N3. The question is whether snoring actually tells you someone is there.
Which Sleep Stages Snoring Happens In
Researchers have measured this directly, by recording snoring through the night alongside a full sleep study.
A small study in the American Review of Respiratory Disease in 1991 compared eight self-described heavy snorers with six people who said they did not snore. The first surprise was that even the "non-snorers" snored lightly. The second was the pattern across the night. Light snorers snored evenly through every sleep stage, while heavy snorers snored more in slow-wave and REM sleep, with their snoring rate highest in slow-wave sleep.
A larger 2012 study in the Journal of Sleep Research looked at 104 people who snored loudly every night, 77 with sleep apnoea and 27 without. In both groups, snoring was louder and more frequent on the back than on the side, whatever the sleep stage. Within any given position, snoring was also usually louder and more frequent in N3 than in N2 or REM sleep.
So there is a real kernel of truth in the myth. For heavy snorers, deep sleep is often when the snoring peaks.
But the same studies show its limits. Snoring also happens in light sleep and in REM. The lighter snorers in the 1991 study snored just as much in light stages as in deep ones. And position mattered in every stage, so a person snoring on their back may simply be on their back.
Hearing someone snore tells you they are asleep. It does not tell you which stage they are in, and it certainly does not tell you they spent the night in deep sleep.
The Twist: Louder Snoring, Fewer Apnoeas
There is a finding that helps explain why heavy snoring and deep sleep go together, and it is not the one most people expect.
A 2009 study in the Journal of Clinical Sleep Medicine analysed every 30 second slice of sleep in 253 consecutive overnight sleep studies, 171 of them in people with obstructive sleep apnoea. Breathing interruptions and arousals fell strikingly from stage 1 through to the deepest stage of non-REM sleep, with REM somewhere in between. In the deepest stage, 82 percent of the apnoea patients had fewer than 15 breathing events an hour, and 57 percent had fewer than 5.
One way to read this alongside the snoring studies is that in deep sleep the airway tends to stay partly open and vibrate, producing steady, loud snoring, rather than repeatedly closing. The lighter stages, where breathing events were more common, are where a vulnerable airway is more likely to cause pauses and arousals.
The same study found something that undercuts the myth more directly. People with sleep apnoea took significantly longer to reach slow-wave and REM sleep than people without it, and spent less time in the deepest stage. The people with the most disordered breathing were getting less deep sleep, not more.
Lying on the side mattered here too. Breathing events and arousals were markedly lower in the side position than on the back in every sleep stage, an effect the authors described as comparable in size to the deep sleep effect.
Arousals: How Snoring Breaks Up Sleep
The real cost of snoring for the snorer is not usually the noise. It is what happens to the continuity of sleep.
When the airway narrows, the body has to work harder to pull air through it. At some point the brain reacts with an arousal, a very short shift towards lighter sleep or waking. The airway opens, breathing recovers, and sleep carries on. Each one is very short, which is why it is easy to miss.
This was described in a landmark 1993 paper in Chest that defined the upper airway resistance syndrome. Its authors studied people whose only complaint was chronic daytime sleepiness. In 15 of them, sleep was fragmented throughout the night by very short arousals of a kind usually ignored in standard sleep analysis. An arousal typically came within one to three breaths of the airway narrowing and restored normal breathing. The breathing changes were limited drops in airflow rather than full pauses.
Yet these people were very sleepy. In a daytime nap test, they fell asleep in an average of 5.1 minutes.
Snoring was present alongside these arousals in 10 of the 15. The authors were clear that snoring was neither necessary nor sufficient to identify the syndrome, but the overlap is the point: the same narrowing that makes the noise can be what is pulling sleep apart. When the airway was held open with CPAP, used experimentally, the arousals fell from about 31 to 8 an hour, the daytime sleepiness went, and the average nap test time rose to 13.5 minutes.
The 1991 snoring study found a related pattern using simpler measures. Overall sleep architecture looked similar in heavy snorers and non-snorers. But the more someone snored, the more time they spent awake after first falling asleep, and the lower their sleep efficiency, the share of time in bed actually spent asleep. The authors concluded that this may have an adverse effect on how heavy snorers function during the day.
Why Snorers Can Wake Up Unrefreshed
If snoring meant deep, restorative sleep, regular snorers should be the most alert people in the morning. The largest study of the question found the opposite.
The Sleep Heart Health Study, reported in the American Journal of Respiratory and Critical Care Medicine in 2000, looked at 2,737 men and 3,040 women with an average age of 64, using home sleep studies to count breathing interruptions. Sleepiness scores rose steadily with how often people snored, from 6.4 on the Epworth scale in current non-snorers to 9.3 in those who snored six to seven nights a week.
The share with excessive daytime sleepiness rose from 15 percent in people who had never snored to 39 percent in those snoring six to seven nights a week.
Crucially, the link between snoring and sleepiness held at every level of breathing interruptions, and it held after adjusting for them, along with age, sex, body mass index and signs of too little sleep. It was not simply that snorers had more apnoea. Snoring itself went with being sleepier.
That kind of study shows an association rather than proving cause. But it fits the arousal picture well. Sleep that is repeatedly nudged towards waking can look like a full night in bed and still leave you tired.
What This Means If You Snore
Do not take the snoring as a compliment. It shows you were asleep, not that you slept well. Heavy snoring tends to peak in deep sleep, but it also runs through the lighter stages, and it can come with arousals you never notice.
Pay attention to how you feel. Waking unrefreshed, nodding off in front of the television, or leaning on caffeine to get through the day despite enough hours in bed are all worth noticing in someone who snores.
Know the signs that need a doctor. Witnessed pauses in breathing, gasping or choking, and heavy daytime sleepiness point towards sleep apnoea rather than simple snoring. Our guide to whether snoring is a sign of sleep apnoea sets out the warning signs and the route to a diagnosis.
Reduce the narrowing. Side sleeping lowered snoring and breathing events in every sleep stage in the studies above. Keeping alcohol away from bedtime helps too, for reasons we covered in why alcohol makes snoring worse. If a blocked nose is part of the problem, nasal strips widen the nostrils mechanically, though they only address the nasal part of the airway. Our wider guide on how to stop snoring while sleeping covers the rest.
Judge the night by the morning. Loud is not the same as deep, and a long night is not the same as a good one. How you feel at eleven in the morning says more about your sleep than how you sounded at two.
Frequently Asked Questions (FAQs)
Does snoring mean you are in a deep sleep?
Not necessarily. Heavy snorers do tend to snore most in deep, slow-wave sleep, but snoring also happens in light sleep and REM. One study found lighter snorers snored evenly across all stages. Snoring tells you someone is asleep, not which stage they are in or how well they are sleeping.
Which stage of sleep do people snore in most?
In studies of loud, nightly snorers, snoring was usually louder and more frequent in stage N3, the deepest stage, than in N2 or REM. Position mattered as well: snoring was louder and more frequent on the back than on the side in every stage. Lighter snorers showed little difference between stages.
Can snoring disturb your sleep without waking you up?
Yes. A narrowing airway can trigger very short arousals, brief shifts towards waking that restore breathing. In the study that defined the upper airway resistance syndrome, these arousals came within one to three breaths of the airway narrowing, and people affected fell asleep in a daytime nap test in about five minutes.
Why do I feel tired even though I sleep all night?
There are many possible causes, and snoring is one worth considering. In a study of nearly 5,800 adults, excessive daytime sleepiness affected 15 percent of people who had never snored and 39 percent of those snoring six to seven nights a week, even after accounting for breathing pauses. Persistent tiredness deserves a conversation with your GP.
Is snoring in deep sleep a sign of sleep apnoea?
Not on its own. In one large analysis, breathing interruptions were actually much lower in the deepest stage of sleep, with 82 percent of apnoea patients below 15 events an hour there. Apnoea shows itself more in lighter stages, through pauses, gasping and daytime sleepiness. Those signs matter more than when the snoring happens.
Does sleeping on your side change this?
It helps in every stage. Snoring was louder and more frequent on the back than on the side regardless of sleep stage, and in people with apnoea, breathing events and arousals were markedly lower on the side in all stages. Side sleeping is one of the simplest ways to reduce the narrowing behind both the noise and the arousals.
Sources
- Hoffstein V et al., Snoring and sleep architecture, American Review of Respiratory Disease, 1991
- Koutsourelakis I et al., Clinical and polysomnographic determinants of snoring, Journal of Sleep Research, 2012
- Ratnavadivel R et al., Marked reduction in obstructive sleep apnea severity in slow wave sleep, Journal of Clinical Sleep Medicine, 2009
- Guilleminault C et al., A cause of excessive daytime sleepiness: the upper airway resistance syndrome, Chest, 1993
- Gottlieb DJ et al., Does snoring predict sleepiness independently of apnea and hypopnea frequency?, American Journal of Respiratory and Critical Care Medicine, 2000
This article is general information, not medical advice. If you snore and feel unrefreshed despite a full night in bed, or someone has seen you stop breathing during sleep, speak to your GP.
