Does mouth breathing cause sleep apnea, or is it the other way round?

Mouth breathing and sleep apnea feed each other. Breathing through the mouth during sleep makes the upper airway easier to collapse, which can make obstructive breathing more likely. Sleep apnea, in turn, pushes people to breathe through the mouth more. So the honest answer to "which causes which" is that the arrow points both ways, and the research on each direction is small but consistent.

This article explains the airway mechanics, what the studies found, why tape isn't a treatment, and what to do if you think you have either problem. It isn't medical advice.

Does mouth breathing cause sleep apnea?

Mouth breathing doesn't cause sleep apnea by itself, but it makes the airway behave worse during sleep. In a 2003 study in the European Respiratory Journal, 12 healthy adults with normal noses slept under two conditions in random order: breathing only through the nose, and breathing only through the mouth. Awake, airway resistance was similar either way. Asleep, it was much higher with mouth breathing, a median of 12.4 compared with 5.2 on the study's resistance scale.

The bigger finding was in breathing events. With oral breathing, obstructive apneas and hypopneas were far more frequent, an average AHI of 43 compared with 1.5 when the same people breathed through the nose. These were healthy volunteers, not people with sleep apnea, and the authors concluded that nasal breathing has a mechanical advantage during sleep that may explain why healthy people breathe almost entirely through the nose at night.

The study forced mouth breathing in a lab, so it doesn't show what happens to someone whose mouth falls open naturally. It does show that the route of breathing matters to how stable the airway is. If AHI is new to you, it's the number of breathing events per hour of sleep.

Why does an open mouth make the airway collapse more easily?

An open mouth changes the shape of the airway behind the tongue. A 1996 study in the American Journal of Respiratory and Critical Care Medicine measured how easily the upper airway collapsed in six healthy sleeping volunteers with the mouth closed and then open.

With the mouth open, the airway collapsed at a less negative pressure, meaning it was easier to close. Total breathing resistance also went up. The researchers' imaging showed the gap between the hyoid bone and the lower jaw shrank when the mouth opened. They concluded that mouth opening increases airway collapsibility during sleep and may contribute to sleep-related breathing problems.

A simple way to picture it is that when the jaw drops, the tongue and soft tissues have less room and sit further back. Our article on why your mouth falls open when you sleep covers the everyday reasons this happens.

Does sleep apnea cause mouth breathing?

Sleep apnea also seems to drive mouth breathing. A 2006 study in the European Respiratory Journal recorded the breathing route of 41 snorers who all had normal nasal resistance, so a blocked nose wasn't the explanation. The 28 with sleep apnea spent more of the night breathing through the mouth, or through mouth and nose together, than the 13 simple snorers.

The more severe the apnea, the more mouth breathing. In the statistical analysis, oral breathing was independently related only to AHI, and AHI was the main factor in combined mouth-and-nose breathing too. The authors concluded that apnea severity is a major determinant of how much time people spend breathing through the mouth.

Lying down adds another push. A 2022 meta-analysis in Laryngoscope found that lying down increases nasal resistance and reduces nasal airflow, with a slightly larger effect in people who snore or have sleep apnea. A nose that feels fine when you're upright may feel tighter in bed, and our guide to why your nose is stuffy at night explains why.

Is mouth breathing a sign of sleep apnea?

Mouth breathing at night can be a sign of sleep apnea, but it isn't proof on its own. NHLBI lists mouth breathing among the night-time signs of sleep apnea in children, alongside snoring, breathing that starts and stops, waking often and bedwetting. In adults, the 2006 study showed people with sleep apnea breathe through the mouth more than snorers without it.

Plenty of people mouth breathe for other reasons, and our guide to why you breathe through your mouth at night covers the common ones. What makes it worth checking is the company it keeps. Mouth breathing together with loud snoring, gasping, pauses someone else notices or heavy daytime sleepiness is a reason to talk to a doctor. Our list of sleep apnea warning signs covers the rest.

Which way does the arrow point?

The research supports both directions, which is why the two are so often found together. This summary sets out what each study tested and what it doesn't tell us.

Does nose breathing help sleep apnea?

Nose breathing is the airway's more stable route during sleep, but shifting to it isn't a treatment for sleep apnea on its own. The best direct test is a 2013 crossover trial of 21 people with sleep apnea and normal nasal resistance when awake. A week of a nasal decongestant combined with a steroid spray reduced mouth breathing, increased nose breathing and lowered AHI by 21% on average compared with a placebo spray.

People whose nose breathing increased most had the biggest drop in AHI. The authors called the improvement modest. Their average AHI at the start was 31 events an hour, so even a 21% fall leaves most people well within the range that needs treatment. The trial also used a decongestant spray, which isn't something to use night after night on your own. Our article on decongestant spray rebound explains why.

What this means in practice is that a clear nose helps, and it's worth sorting out congestion. But it works alongside proper sleep apnea treatment, not instead of it. For everyday ways to clear your nose before bed, see how to unblock your nose before bed.

Why isn't mouth tape a treatment for sleep apnea?

Mouth tape isn't a sleep apnea treatment because the evidence doesn't support it, and it carries a specific risk. A 2025 systematic review in PLOS One looked at 10 studies with 213 people in total. Two reported improvements in sleep apnea measures, while others found no difference. Several discussed a possible risk of asphyxiation when the mouth is taped and the nose is blocked, and many excluded anyone with nasal obstruction.

The review concluded there seems to be a potentially serious risk of harm for people taping indiscriminately, and that more studies are needed to find any clinical benefit. One of the studies it covers is a small 2022 study in Healthcare whose 20 participants were mouth breathers with mild sleep apnea. It had no comparison group, lasted one week, and enrolled only people who tolerated having their mouths sealed, so it can't tell us whether tape treats anything.

There is one setting where tape has been studied with sleep apnea treatment rather than instead of it. A 2025 randomized crossover trial in the Journal of Clinical Sleep Medicine gave 62 people who breathed through the mouth on CPAP a month with mouth tape and a month without. With tape, they used their CPAP for about 52 minutes a day longer on average, and reported less mouth and throat dryness. That's a question to raise with your sleep doctor if you're already on CPAP; our guide to mouth tape and CPAP has more.

We don't recommend mouth tape for children. NHLBI lists mouth breathing among the night-time signs of sleep apnea in children, so a child who sleeps with their mouth open should see a doctor.

What should you do if you mouth breathe at night?

If you breathe through your mouth at night, start by working out why. A blocked nose, a jaw that drops open, and sleep apnea are the most common reasons, and they need different responses.

Start with sleep apnea. Loud snoring, gasping or choking, pauses in breathing that someone else notices, and heavy daytime sleepiness all point toward a sleep evaluation rather than home fixes. Our guide to snoring vs sleep apnea helps you tell them apart, and a home sleep apnea test may be an option.

Next, look after your nose. If it's often blocked, ask a doctor or pharmacist what's behind it, since the 2013 trial suggests a clearer nose shifts more of the night's breathing to the nasal route.

If you do have sleep apnea, get it treated. NHLBI says a PAP machine is the most common treatment, and options also include oral devices, nerve stimulation and surgery. Our overview of sleep apnea treatment options explains each one.

If you're already on CPAP and still breathe through your mouth, tell your sleep team. The 2025 trial suggests mouth tape is worth asking about in that setting, alongside the mask and settings you already use.

Read next

• Why do I breathe through my mouth at night?
• Sleep apnea treatments explained
• Nasal vs mouth breathing: what's the difference?

* This content is for informational and educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease or health condition. Talk to a qualified healthcare provider about your health.