Snoring

Many factors may contribute to snoring, including:

Insufficient muscle tone of the palate, tongue, and pharynx

• This is the cause of most adult-onset snoring.[11]Fairbanks DNF, Mickelson SA, Woodson BT, eds. Snoring and obstructive sleep apnea. 3rd ed. Philadelphia, PA: Lippincott, Williams & Wilkins; 2003. The effect is exaggerated by alcohol, sedating medications, hypothyroidism, and neurological disorders such as cerebral palsy.

Increased compliance of pharyngeal tissues

• This predisposes to collapsibility and snoring. This is most commonly associated with aging, but rarely may be associated with muscle-tone reducing conditions (e.g., cerebral palsy).

Increased extraluminal pressure

• For example, caused by fat deposits in the neck.

Space-occupying masses

• In obese patients, fat deposits in the pharyngeal and neck tissues cause narrowing of the air passages.

• Large tonsils compromise the airway. Adentonsillar hypertrophy is the main cause of snoring in children.

• Patients with Down syndrome and acromegaly often have tongue enlargement.

• Cysts and tumors are uncommon causes.

Skeletal abnormalities

• For example, retrognathia (receding chin) or micrognathia (small chin) prevents the tongue from being positioned sufficiently forward during sleep.

Excessive length of the soft palate and uvula

• This narrows the nasopharyngeal aperture predisposing to snoring.

Restriction of nasal airflow

• This causes increased negative pressure in the upper airway beyond the nose, which predisposes to airway collapse and snoring.

• Deformities of the nose and septum, turbinate hypertrophy, nasal polyps, and sinonasal tumors are all possible nasal causes of snoring.[11]Fairbanks DNF, Mickelson SA, Woodson BT, eds. Snoring and obstructive sleep apnea. 3rd ed. Philadelphia, PA: Lippincott, Williams & Wilkins; 2003.

Snoring originates in the collapsible part of the airway that has no rigid support. This part extends from the choanae to the epiglottis. The Bernoulli principle states that with a flow a negative pressure develops at the periphery of the flow, and as the flow velocity increases so does the negative pressure.

Consequently, when an airway narrows for any reason, the airflow velocity across the narrowing has to increase and as a result the negative pressure also increases.

When the negative intraluminal pressure in the pharynx exceeds the ability of the dilator muscles to hold the pharynx open, they collapse and partial obstruction occurs, with consequent turbulent airflow, vibrations of the upper airways, and generation of a snoring noise.

The vibrations usually occur in the soft palate, but in approximately 30% of patients with nonapneic snoring, vibrations may also be present at other sites including the tonsils, epiglottis, and base of the tongue.[12]Gleeson M, Ed. Scott-Brown's otorhinolaryngology: head and neck surgery. 7th ed. London: Hodder Arnold; 2008: 2305-39.

Nasal obstruction increases the negative intraluminal pressure in the pharynx during inspiration and hence predisposes to snoring.[11]Fairbanks DNF, Mickelson SA, Woodson BT, eds. Snoring and obstructive sleep apnea. 3rd ed. Philadelphia, PA: Lippincott, Williams & Wilkins; 2003. Also, nasal obstruction may result in mouth-breathing, which causes the tongue to fall backward, causing obstruction and snoring.

Clinical classification

Simple snoring:

• Defined as snoring without obstructive apneas or frequent arousals from sleep and without gas exchange abnormalities.[1]American Academy of Sleep Medicine. The AASM international classification of sleep disorders - third edition, text revision (ICSD-3-TR). Jun 2023 [internet publication]. https://aasm.org/clinical-resources/international-classification-sleep-disorders ​ It is generally considered benign.

Primary snoring:

• Defined as snoring without complaints of daytime sleepiness and an apnea-hypopnea index (AHI) of below 5 episodes per hour (AHI = number of apneas and hypopneas per hour).[2]Savage CR, Steward DL. Snoring: a critical analysis of current treatment modalities. Does anything really work? Curr Opinion Otolaryngol Head Neck Surg. 2007 Jun;15(3):177-9. http://www.ncbi.nlm.nih.gov/pubmed/17483686?tool=bestpractice.com

Upper airway resistance syndrome (UARS):

• Applies to individuals with increased inspiratory efforts with frequent arousals but without overt apneas and hypopneas. The fragmented sleep results in increased daytime sleepiness.

Obstructive sleep apnea:

• Characterized by episodes of complete or partial upper airway obstruction during sleep. Episodic airway obstruction is usually associated with oxyhemoglobin desaturations and arousals from sleep. Symptoms include chronic snoring, insomnia, gasping and breath holding, unrefreshing sleep, and daytime sleepiness.[3]Sateia MJ. International classification of sleep disorders-third edition: highlights and modifications. Chest. 2014 Nov;146(5):1387-94. http://www.ncbi.nlm.nih.gov/pubmed/25367475?tool=bestpractice.com Diagnosis is confirmed if the AHI or Respiratory Distress Index (number of apneas, hypopneas, and respiratory effort-related arousals per hour) established with polysomnography or portable sleep test is ≥15 episodes/hour. However, 5 episodes/hour is considered sufficient for diagnosis if additional symptoms or comorbidities are present.