The Science Behind Snoring

The science behind snoring starts with anatomy: snoring is the sound of air forcing through a narrowed upper airway during sleep, anywhere from the nostrils to the vocal cords. Occasional snoring after a tiring day is physiological. Snoring every night with unrefreshing sleep warns of fragmented sleep and, often, obstructive sleep apnoea (repeated narrowing or closure of the airway during sleep), which raises the risk of hypertension, diabetes and accidents.

Dr. Trisha Srivastava, Consultant, ENT, Artemis Hospitals, Gurugram, India, calls snoring a very common and very ignored symptom. Her central argument is that the damage from poor sleep is slow. It takes years for the metabolic effects to show, and patients who develop diabetes mellitus or hypertension early rarely connect it to the fact that they have not been sleeping adequately for a long time. This guide sets out what causes snoring: where in the airway it starts, what it does to the architecture of sleep, how it looks in adults and in children, and when it deserves a specialist's attention.

Why snoring is an ignored symptom

Most people treat snoring as a social nuisance rather than a medical sign. The common attitude, as Dr. Srivastava describes it, is that a little snoring is no great matter and only the partner is disturbed. That attitude misses what snoring represents: a night of interrupted breathing and broken sleep.

The consequences build quietly. A person who does not sleep well for years accumulates metabolic and cardiovascular strain, and the first visible signs may be a rising blood pressure reading or a new diagnosis of diabetes, long before anyone thinks to ask about sleep. Sleep quality therefore belongs in the history of any patient with these conditions, especially younger ones.

Three patients, one symptom

Dr. Srivastava illustrates the problem with three clinical scenarios. All three patients complain of the same thing, snoring and poor sleep, yet each has a different cause.

• The sedentary man with obesity. A 42-year-old man with a sedentary lifestyle and a body mass index of around 34 sleeps seven to eight hours a night but wakes unrested, with brain fog, irritability and tiredness through the day. Examination shows obesity, a thick neck, and a bulky tongue and palate.
• The athletic man with nasal allergy. A 28-year-old man exercises regularly and is fit, but has nasal allergies. Whenever he lies down to sleep, his nose blocks, he cannot breathe through it, and he ends up snoring and breathing through his mouth.
• The woman with a sensitive throat. A 35-year-old woman with a normal body mass index and no nasal complaints has a throat that reacts to changes in weather and to cold or sour food. She snores at night, her sleep is not badly disturbed, but she wakes unrefreshed with a very sore throat that eases as the day goes on.

The lesson is that snoring is a symptom with several phenotypes, not a diagnosis. Treating all three patients the same way would fail at least two of them. Each needs an examination that finds where the airway narrows and why.

The science behind snoring: where the airway narrows

Dr. Srivastava is clear that not every snorer should be labelled as having obstructive sleep apnoea. Any blockage along the passage that runs from the nasal vestibule (the entrance of the nostril) down to the level of the vocal cords can cause snoring and fragmented or disturbed sleep. The common sites are:

• The nose: a deviated nasal septum (the partition between the nostrils is bent to one side), turbinate hypertrophy (enlargement of the bony and soft-tissue ridges on the side walls of the nose) or nasal polyps.
• The nasopharynx (the space behind the nose): enlarged adenoids.
• The oropharynx and retropalatal area (the space behind the soft palate): bulky tissue, or large tonsils, narrowing the airway.
• The base of the tongue: the tongue falling back and squeezing the airway.

The retropalatal area and the tongue base are the two levels that define obstructive sleep apnoea in her framework. The obstruction there can be partial or complete. A partial obstruction is called a hypopnoea; a complete obstruction is called an apnoea. In standard sleep scoring, an apnoea is a fall in airflow of 90% or more lasting at least 10 seconds, and a hypopnoea is a fall of at least 30% lasting at least 10 seconds, accompanied by a drop in oxygen saturation or an arousal from sleep.

Sleep stages and cycles: what normal sleep looks like

Understanding why snoring matters requires understanding what sleep is meant to achieve. Sleep has two broad states: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM sleep is divided into three stages, N1, N2 and N3, and each stage is deeper than the one before.

Dr. Srivastava sets out the structure of a normal night:

• Every individual passes through four to five sleep cycles a night, and each cycle lasts around 90 to 110 minutes.
• N1 is the lightest sleep. Someone woken from N1 wakes at once, without brain fog or fatigue. It makes up only about 5% of the night.
• N2 and N3 together make up the majority of sleep, around 70 to 75% of the night.
• REM sleep follows. It is the stage of vivid dreaming.

What deep sleep does for the body

Stage 3 of NREM sleep is the stage of physical recovery. Most growth hormone is released at night, with the largest pulse during N3, and it helps heal the muscle wear and tear of the day. In N3 the autonomic nervous system shifts its tone from sympathetic (the "fight or flight" system) to parasympathetic (the "rest and digest" system), so heart rate and blood pressure fall.

REM sleep has a different job. Together with deep NREM sleep, it helps convert the day's memories into long-term memory, and it supports emotional stability.

Across all its stages, sleep regulates hormones, maintains the cardiovascular system, strengthens immunity, consolidates memory and clears metabolic waste from the central nervous system. Snoring matters because it interferes with each of these functions.

What fragmented sleep does to the body

When the airway repeatedly narrows or closes, the sleeper is pulled back towards lighter sleep. Dr. Srivastava explains that a person who cannot attain good sleep does not reach stage 3. They remain in stages 1 and 2, with a little REM sleep, and the restorative work of deep sleep does not happen. The consequences fall into two groups.

Cardiovascular complications. Patients develop hypertension earlier than expected, and arrhythmias (irregular heart rhythms).

Neurocognitive impairment. Patients feel sleepy through the day, concentrate poorly and lose cognitive sharpness. The risk of accidents rises, particularly when the person is driving or operating heavy machinery.

Symptoms of fragmented sleep and sleep apnoea

The symptoms Dr. Srivastava lists are worth knowing, because several are noticed by a bed partner rather than the patient:

• Snoring at night.
• Episodes of stopped breathing witnessed by the partner, followed by an arousal.
• Gasping or choking during the night.
• Excessive daytime sleepiness.
• Morning headache.
• Irritability and mood swings.

Snoring in children is not normal: paediatric sleep apnoea

Snoring is often assumed to be an adult problem. Dr. Srivastava stresses that a good share of obstructive sleep apnoea occurs in children. Between about one year and eight or nine years of age, children can have large adenoids and large tonsils, and either can obstruct breathing during sleep.

These children typically breathe through the mouth, snore and are restless at night, tossing and turning in bed. The effects carry into the day:

• Poor performance at school.
• Daytime hyperactivity.
• Impaired growth.

Growth is the point parents notice. Dr. Srivastava describes parents who bring a child who eats well but does not gain height or weight. The explanation is that the child is not reaching deep sleep, so growth hormone is not produced properly and the child does not gain height and weight as expected.

The treatment she provides in this age group is surgical removal of the tonsils and adenoids. The adenoids are cleared from the nasopharynx with coblation, a technique that uses radiofrequency energy passed through saline to remove tissue at a lower temperature than conventional electrocautery.

When is snoring normal, and when is it a problem?

Not every episode of snoring is a pathology, and Dr. Srivastava is explicit about this. Someone who has had an exhausting day may snore that night, and that is physiological. Snoring during a common cold or a sore throat, lasting a week or 15 days and then settling, is also understandable.

The picture changes when snoring becomes chronic: it happens every night, the person sleeps with the mouth open, wakes tired and lacks energy for the day. Snoring loud enough that family members complain is another signal. At that point, in her view, the right step is an ENT examination to check whether there is a structural cause and whether a sleep study is needed.

She also frames the condition as both structural and physiological. In some patients, examination finds a clear anatomical block, such as a badly deviated septum in an otherwise lean person, and correcting it resolves the snoring. In others, nothing in the nose or palate is at fault, and the problem is a thick neck and excess weight, where lifestyle change comes first.

Assessment and treatment at a glance

Dr. Srivastava's approach is to tailor treatment to each patient. Assessment starts with validated questionnaires, continues with a thorough ENT examination including nasal endoscopy and awake video laryngoscopy, and adds a sleep study where needed. The full pathway, including the levels of sleep study and the role of drug-induced sleep endoscopy, is set out in how obstructive sleep apnoea is diagnosed.

Treatment options include lifestyle change, positive airway pressure machines and surgery, and they are used in combination rather than as alternatives. The differences between CPAP and BiPAP, and the surgical procedures for the nose, tonsils and palate, are covered in CPAP vs BiPAP and the other treatment options.

The questions doctors asked during the session, on sleep stages, alcohol, referral and the definition of a thick neck, are answered in the Live Discussion. More on Dr. Srivastava's practice is on her profile, and related conditions are under ENT.

Her closing principle applies to every snoring patient: look intently at what is actually bothering the patient before deciding what to treat.