Dry Air, Blocked Noses, and Broken Sleep

Most of us accept a blocked nose in winter as an inevitable seasonal inconvenience, something to be managed with tissues, steam, and patience until the cold passes. But for your upper airway during sleep, nasal obstruction is far more than an inconvenience. It is a physiological disruption that can trigger mouth breathing, worsen snoring, aggravate obstructive sleep apnoea, and fragment sleep in ways that accumulate into a significant health burden. Understanding why this happens, and what you can do about it, could transform your winter nights.

Why the Nose Matters So Much During Sleep

Nasal breathing is the physiologically preferred route during sleep. During normal nasal breathing, incoming air is warmed, humidified, filtered, and directed through the nasal passages in a smooth, laminar flow. Crucially, the act of breathing through the nose activates a set of protective reflexes, including the negative pressure reflex, that increase the activity of the upper airway dilator muscles, the muscles responsible for keeping the throat open during sleep.¹

When the nose is working well, these mechanisms work together to maintain an open, stable airway throughout the night. When the nose is blocked, whether by a cold, allergies, a deviated septum, or the inflammation caused by dry winter air, this entire system is disrupted.

The Starling Resistor: What Happens When the Nose Is Blocked

The physics of what happens to the upper airway when nasal congestion is present is explained by what researchers call the Starling resistor model. The upper airway functions like a tube with a partial obstruction at the entrance, the nose - and a collapsible segment downstream - the pharynx, or throat. When nasal resistance increases due to congestion or obstruction, a suction force is generated downstream in the throat. This negative pressure pulls the pharyngeal walls inward, increasing the tendency of the airway to collapse during inhalation.¹

Research published in PLOS One confirmed this mechanism using computational fluid dynamics, demonstrating that oral breathing - the switch that occurs when nasal congestion becomes too severe - significantly increases airflow velocity and turbulence through the pharynx, dramatically increasing the likelihood of airway collapse.² This is why a blocked nose that forces mouth breathing during sleep doesn't just make breathing feel harder, it mechanically predisposes the upper airway to collapse, snoring, and apnoea events.

Mouth Breathing: When the Bypass Becomes the Problem

When nasal resistance exceeds a certain threshold, the body instinctively opens the mouth to create an alternative breathing route. During wakefulness, this is a manageable compensation. During sleep, it creates a cascade of problems.

Mouth breathing during sleep bypasses the nasal ventilatory reflex that keeps upper airway dilator muscles active.¹ Without this reflex activation, the muscles of the throat relax more completely, making the airway more prone to collapse. Research confirms that upper airway resistance is lower during sleep when breathing through the nose compared to the mouth, and that mouth opening significantly increases pharyngeal collapsibility.² The result is more frequent snoring, more severe vibration of the soft palate and uvula, and in predisposed individuals, more frequent obstructive apnoea events - all triggered by the simple act of breathing through the mouth instead of the nose.

Additionally, mouth breathing dries out the throat and oral tissues, causing inflammation and swelling that further narrows the airway and increases snoring. It also bypasses the nose's natural humidification of inhaled air therefore compounding the drying effects of indoor heating on the airways overnight.

Nasal Congestion and Sleep Apnoea: The Research Is Clear

The link between nasal obstruction and obstructive sleep apnoea is well established in the scientific literature. A review published in the International Journal of Otolaryngology found that nasal obstruction is significantly associated with obstructive sleep apnoea syndrome, with multiple studies demonstrating increased nasal resistance in OSA patients compared to controls.³ Crucially, experimental induction of nasal obstruction in healthy subjects, blocking the nasal passages with gauze in controlled studies has been shown to produce obstructive apnoea events in people who did not previously have sleep apnoea.³

This means that for people who already have mild or borderline sleep apnoea, a winter cold or bout of nasal congestion can temporarily but significantly worsen the severity of their condition, producing apnoea events that weren't present before, and deepening the fragmentation of sleep that comes with each one.

The Fragmented Sleep Nobody Remembers

One of the most important and underappreciated consequences of nasal congestion and mouth breathing during sleep is fragmented sleep architecture. Nasal congestion causes frequent micro-arousals - brief awakenings too short to be remembered but sufficient to disrupt the normal progression through sleep stages. These micro-arousals interrupt the 90-minute sleep cycles required for restorative NREM and REM sleep, leaving the person feeling unrested despite what seems like adequate time in bed.³

Over a winter in which congestion persists for weeks or months, whether from recurrent colds, sinusitis, or allergic rhinitis, this fragmentation accumulates into a sustained period of poor sleep quality with real consequences for energy, mood, cognitive function, and immune health.

What You Can Do Right Now

Several practical strategies can help maintain nasal airway patency and reduce mouth breathing during winter nights. Saline nasal irrigation (using a saline spray or nasal rinse) is one of the most evidence-backed and safest options for clearing the nasal passages and reducing mucosal inflammation, without the rebound congestion risk associated with decongestant sprays. A bedroom humidifier reduces the drying effects of indoor heating on nasal and throat tissues. Staying well hydrated keeps mucous secretions fluid and less obstructive. Treating underlying allergic rhinitis with appropriate antihistamine or nasal corticosteroid therapy can significantly reduce the nasal swelling that worsens winter snoring.

Sleeping position matters too. Sleeping on your back allows the tongue and jaw to fall backward under gravity, narrowing the airway and compounding the effects of nasal obstruction. Side sleeping reduces this gravitational effect and is particularly helpful when nasal congestion is present.

When the Problem Is Bigger Than a Blocked Nose

If nasal congestion is consistently triggering loud snoring, witnessed breathing pauses, gasping arousals, or morning fatigue that doesn't resolve as the congestion clears, the congestion may be unmasking an underlying obstructive sleep apnoea that deserves clinical investigation. A sleep study, which can now be conducted at home, is the only way to establish the true severity of the problem and guide the most appropriate treatment.

At SleepWise Clinic, our sleep medicine dentists understand the relationship between nasal health and airway stability during sleep. A custom oral appliance works by mechanically maintaining airway opening regardless of nasal breathing status, providing a layer of protection against the kind of airway collapse that nasal congestion promotes, winter or otherwise.

Call SleepWise Clinic on 1300 101 505 or take our free online sleep apnoea test today — because better breathing starts with understanding your airway.

Request for references: 1. Annals of Allergy, Asthma & Immunology. (2015) 2. Zhao X et al. (2020) 3. Michels DS et al. (2014)