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Sleep / Series · How snoring happens, part 1

Why does the airway narrow during sleep?

Introductory · 4 min read · ■■■□ moderate evidence

By: NefeslyFirst published: 18 October 2026Last updated: 29 October 2026Editor: support@nefesly.com

When you breathe while awake, your throat stays open all the time. You do this without thinking. Once you fall asleep, things change a little. In this article we explain why, step by step.

The throat is like a flexible hose

Part of the passage from the nose to the lungs is surrounded by bone. The back of the throat is not. It is lined by soft tissues such as the tongue, the soft palate (the soft back part of the roof of the mouth) and the uvula. This section is like a flexible hose with air running through it.

When you breathe in, the pressure inside drops, and the walls of the hose are pulled inwards. While you are awake, the throat muscles resist this and keep the airway open. During sleep, the response of these muscles can weaken1,2.

What happens as you fall asleep?

As you fall asleep, some of these muscles relax. In a study of the tongue muscle, about half of the nerve cells that fire with each breath fell completely silent at the moment of falling asleep2. When the muscles relax, the throat narrows a little.

In most people this narrowing goes unnoticed. In some, though, the air passing through the narrow gap makes the soft tissues vibrate. The sound of this vibration is snoring3.

The stage of sleep may also play a part. In some people with mild or moderate sleep apnea, breathing problems are concentrated in the dreaming stage (REM)4.

What changes when you lie on your back?

When you lie on your back, gravity can pull the tongue and soft palate backwards. In measurements in people with sleep apnea, the throat closed more easily when lying on the back than when lying on the side5. We cover this in detail in Does sleep position affect snoring?

Is everyone's throat the same?

No. Some people are born with a narrower airway. Large tonsils can also narrow it1. Being male, age and weight also affect how easily the throat closes during sleep6.

The narrowing cannot be explained by the shape of the throat alone. How well the muscles respond during sleep and how easily the brain wakes up also matter, and these traits vary a great deal between people7. So two people with similar throats can have very different nights.

From narrowing to blockage

You can think of how easily the throat closes during sleep as a range. At one end are people who only snore. In the middle are those whose breathing becomes shallow at times, and at the other end those whose breathing stops for short periods. In one study, these three groups lined up in exactly this order by how easily the throat collapsed8.

So snoring and pauses in breathing are different points on the same path. But not everyone who snores goes to the end of that path. Snoring is very common and usually not a sign of a serious problem9. We explain the difference in the second part of the series, The difference between snoring and sleep apnea.

When to see a doctor?

If someone has seen your breathing stop in your sleep, or you are very sleepy all day, see a doctor. When to see a doctor · Sleep centres in Türkiye

In depthmechanisms, studies, limitations

The pharyngeal airway is a collapsible segment without bony support. Its patency depends on the interaction of factors such as a small lumen, dilator muscle function, the arousal threshold and the stability of ventilatory control1.

The standard measure of collapsibility is the critical closing pressure (Pcrit): the nasal pressure at which maximal inspiratory flow falls to zero as nasal pressure is lowered. In NREM sleep, Pcrit was −6.5 ± 2.7 cm H2O in asymptomatic snorers, −1.6 ± 1.4 in patients with obstructive hypopnea and +2.5 ± 1.5 in patients with obstructive apnea8. In a study of 164 people, sleep apnea was largely absent when passive Pcrit was below −5 cm H2O; above this threshold severity rose markedly6. With BMI, age and disease severity matched, passive Pcrit was 1.9 cm H2O lower in women (95% CI 0.1 to 3.6)6.

The effect of position is marked: in 16 men with OSA, Pcrit in light sleep was 0.6 ± 0.8 cm H2O supine and −2.2 ± 3.6 cm H2O lateral5. In the same small sample, sleep stage had no significant effect on Pcrit5.

At sleep onset (the alpha to theta transition), about 50% of the inspiratory motor units of the genioglossus fell completely silent; tonic and expiratory units were not affected2.

Anatomy is not the only determinant. In a phenotyping study of 75 participants, Pcrit was 0.3 [−1.5 to 1.9] cm H2O in people with OSA and −6.2 [−12.4 to −3.6] cm H2O in controls7. Among people with OSA, 36% had a minimal genioglossus response, 37% a low arousal threshold and 36% a high loop gain7. Non-anatomical traits were proposed to play an important role in 56% of patients7.

Limitation: Pcrit measurement is specific to research settings, and the samples of these studies are small.

Sources

  1. Jordan AS, McSharry DG, Malhotra A. Adult obstructive sleep apnoea. The Lancet. 2014;383(9918):736-747. doi:10.1016/s0140-6736(13)60734-5
  2. Wilkinson V, Malhotra A, Nicholas CL et al. Discharge patterns of human genioglossus motor units during sleep onset. Sleep. 2008;31(4):525-533. doi:10.1093/sleep/31.4.525
  3. Pevernagie D, Aarts RM, De Meyer M. The acoustics of snoring. Sleep Medicine Reviews. 2010;14(2):131-144. doi:10.1016/j.smrv.2009.06.002
  4. Joosten SA, Hamza K, Sands S et al. Phenotypes of patients with mild to moderate obstructive sleep apnoea as confirmed by cluster analysis. Respirology. 2012;17(1):99-107. doi:10.1111/j.1440-1843.2011.02037.x
  5. Penzel T, M\"oller M, Becker HF et al. Effect of sleep position and sleep stage on the collapsibility of the upper airways in patients with sleep apnea. Sleep. 2001;24(1):90-95. doi:10.1093/sleep/24.1.90
  6. Kirkness JP, Schwartz AR, Schneider H et al. Contribution of male sex, age, and obesity to mechanical instability of the upper airway during sleep. Journal of Applied Physiology. 2008;104(6):1618-1624. doi:10.1152/japplphysiol.00045.2008
  7. Eckert DJ, White DP, Jordan AS et al. Defining phenotypic causes of obstructive sleep apnea. Identification of novel therapeutic targets. American Journal of Respiratory and Critical Care Medicine. 2013;188(8):996-1004. doi:10.1164/rccm.201303-0448OC
  8. Gleadhill IC, Schwartz AR, Schubert N et al. Upper airway collapsibility in snorers and in patients with obstructive hypopnea and apnea. American Review of Respiratory Disease. 1991;143(6):1300-1303. doi:10.1164/ajrccm/143.6.1300
  9. NHS. Snoring. https://www.nhs.uk/conditions/snoring/
Cite

APA 7

Nefesly. (2026, October 18). Why does the airway narrow during sleep? Nefesly. Retrieved: 30 October 2026, https://nefesly.com/en/guide/why-does-the-airway-narrow-during-sleep/

BibTeX

@misc{nefesly2026whydoestheairwaynarrowduringsleep,
  author = {{Nefesly}},
  title = {Why does the airway narrow during sleep?},
  year = {2026},
  howpublished = {\url{https://nefesly.com/en/guide/why-does-the-airway-narrow-during-sleep/}},
  note = {Last updated 2026-10-29; accessed 2026-10-30}
}

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Corrections

  • 2026-10-23: English version published.
  • 2026-10-29: For children layer added.

Disclosure: This article has no sponsor.