Snoring

In the International Classification of Sleep Disorders third edition (ICSD-3), snoring is listed under "Isolated symptoms and normal variants" in the section "Sleep-related breathing disorders". The manual defines snoring as "a respiratory sound generated in the upper airway during sleep that typically occurs during inspiration but may also occur in expiration." Primary snoring is not associated with episodes of sleep apnea (cessation of breathing), hypopnea, respiratory-effort related arousals, or hypoventilation. especially primary snoring in children. For example, there is evidence that primary snoring causes excessive daytime sleepiness, Snoring has been classified according to apnea–hypopnea index score and severity of associated sleep disorders. Therefore, snoring as a symptom exists as a spectrum of severity, with primary snoring being the least severe, snoring with upper airway resistance syndrome being of intermediate severity, and snoring associated with obstructive sleep apnea being the most medically significant. Stertor is low-pitched, and can occur when breathing in, out or both. Stertor and stridor can occur together, such as when adenotonsillar hypertrophy and laryngomalacia occur together. ==Mechanism==

Snoring has been mathematically modelled wherein the upper airway is a tube which has an elastic or collapsible section. As the section of the upper airway narrows, resistance to the flow of air increases. This obstruction and reopening occurs at approximately 50 times per second, which causes vibration and noise. The airflow becomes unstable and turbulent. The structures that obstruct the airway and vibrate are various soft tissue structures at different levels along the upper respiratory tract or aerodigestive tract. These are the uvula, soft palate, faucial pillars (palatoglossal arch, palatopharyngeal arch), palatine tonsils, adenoid tonsil, walls of the pharynx, epiglottis, or lower structures. These structures may relax during sleep and move position, especially under the influence of gravity. This results in partial obstruction (narrowing) or complete obstruction of the airway. Partial obstruction of the airway is more associated with primary snoring, whereas complete obstruction is more a feature of obstructive sleep apnea. The following structures were found to vibrate during snoring: soft palate in 100% of cases, pharynx (53.8%), lateral pharyngeal wall (42.3%), epiglottis (42.3%), and tongue base (26.9%). In primary snoring there may be vibration of the soft palate alone, termed "palatal fluttering". In mild to moderate obstructive sleep apnea, there may be vibration of the palate and lateral pharyngeal wall. In severe obstructive sleep apnea, there may be vibration of the tongue base and epiglottis in addition to the above structures. The snoring sound mainly occurs during inhalation (breathing in), but it may occur during exhalation (breathing out). Snorers have more negative pressure in their airway, increased inspiratory time, and limitation of respiratory flow. On polysomnography, snoring is usually louder during slow-wave sleep (stage 3 non-rapid eye movement sleep) or rapid eye movement sleep. Snoring in obstructive sleep apnea usually occurs when airflow turbulence is maximum, which is during hyperpnea episodes at the end of apnea events (breathing cessation). ==Causes==

Snoring (stertor) is often considered according to the location (level) of structure that is causing the obstruction and vibration. However, the sites causing the snoring vary from one person to the next, and the same individual may have multiple different sites which are contributing to the problem. Nasal cavity While it is generally not possible for the rigidly supported structures inside the nose to vibrate, the patency of the nasal airway is important in the development of snoring. The external nasal valve is the tissue immediately around the nostril. Nasal valve collapse refers to weakening or narrowing of the supporting cartilage at the nasal valves. As per the Hagen–Poiseuille equation, a minimal reduction in the diameter of a tube (in this case the nasal airway) results in an exponential change in airflow. Nasal valve collapse is a cause of snoring. In one study, 18% of people with mouth breathing reported awareness of snoring. The oropharynx is a common site which causes snoring noises. An enlarged tongue, termed macroglossia, is a potential cause for snoring. Alcohol Alcohol causes muscle relaxation via its depressant effect on the central nervous system. This muscle relaxation seems to be more pronounced for the tongue, Pregnancy Sometimes snoring starts during pregnancy. Hereditary factors Some people have a genetic predisposition to snoring, a proportion of which may be mediated through other heritable lifestyle factors such as body mass index, smoking and alcohol consumption. The DLEU1 gene (part of BCMS) has been linked to snoring. ==Possible consequences==

Most people with primary snoring do not have any significant health problems as a result of the snoring. In one study, treatment of snoring in males (with continuous positive airway pressure) resulted in 13% better sleep efficiency and an average of 1 hour of extra sleep for their female sleeping partners. and 28% increased risk of coronary artery disease / ischemic heart disease (probably in part explained by snoring with obstructive sleep apnea). Impaired balance between the sympathetic and parasympathetic nervous system may also be involved. This may be related to cerebral hypoxia, hypercapnia, and temporary increased intra-cranial pressure. Snoring is associated with respiratory event-related arousals, which may be connected with headache. Gastroesophageal reflux disease Snoring and obstructive sleep apnea are associated with higher rates of gastroesophageal reflux disease, including acid reflux which occurs during sleep. There is increased negative pressure in the thoracic cavity during apneic episodes. It was suggested that this negative pressure may overcome the lower esophageal sphincter and allow stomach contents to reflux into the esophagus. However, the lower esophageal sphincter was found to be stronger during obstructed breathing events. Another theory which explains the connection is that snoring and obstructive sleep apnea may promote transient lower esophageal sphincter relaxations. Enlarged tonsils are also seen in gastroesophageal reflux disease, and this may contribute to airway restriction and snoring. Sleep bruxism There is conflicting evidence for and against a possible connection between snoring and sleep bruxism (teeth grinding during sleep). It may be that in snoring and obstructive sleep apnea, there are periods of activation of oropharyngeal muscles. These are necessary to restore patency of the collapsed / obstructed airway. This muscle activity may also trigger activity in the muscles of mastication and hence sleep bruxism. Dry mouth There is limited and contradictory evidence for a connection between snoring and xerostomia (dry mouth). Tissue biopsies of the uvula have been carried out on heavy snorers and people with severe obstructive sleep apnea. The biopsies showed abnormal minor salivary glands. There was increased volume of mucous salivary glands and reduced quantity and volume of serous salivary glands. This may cause reduced production of saliva. Snorers also tend to breathe through their mouths during sleep, in order to get more air. This may have a drying effect in the mouth. Other Nerve damage may occur in the soft palate as a result of chronic trauma from vibration. This leads to morphological changes in the palate. ==Diagnosis==

According to ICSD-3, primary snoring may diagnosed with the following diagnostic criteria: Other investigations may sometimes be done, such as nasal function testing (e.g., rhinomanometry), pharyngeal manometry, allergy testing, acoustic analysis, or medical imaging. ==Treatment==

Almost all treatments for snoring revolve around lessening the noise and improving air flow by reducing the blockage in the airway. Lifestyle modification Lifestyle changes are a first-line treatment to stop snoring. Recommended lifestyle changes include stopping smoking, and sleeping on the side (lateral position). Myofunctional therapy is theorized to improve the tone and positioning of the muscles. When myofunctional therapy combined with CPAP is compared to myofunctional therapy alone, there may be little to no difference. There is insufficient evidence to recommend myofunctional therapy for snoring in adults. Myofunctional therapy may be more useful in children who snore than in adults. Dental appliances Dental appliances are common treatments for snoring. They may be custom made, which requires an impression of the teeth and construction in a dental laboratory, or they may be bought over the counter without involvement of a dental health professional. The latter type are often "boil and bite" appliances which come in a set size. The appliance is immersed in boiling water and then the individual bites into appliance with the jaw in a protruded position. Oral appliances may be titratable (adjustable) or non-titratable (one fixed position). In general, oral appliances are cheap and non-invasive. They can be combined with CPAP treatment. Complications include discomfort, excessive salivation (drooling), insomnia, pain in the periodontal ligament of teeth if they are under excessive force, pain in the temporomandibular joint and muscles of mastication (e.g. temporalis), and jaw dislocation. Some devices prevent anterior oral seal, and therefore cause mouth breathing with the associated problems like dry mouth. A device which covers only some of the teeth and leaves others uncovered may potentially have a Dahl effect, leading to undesired movement of the teeth and creating problems like open bite. Therefore, a dentist should regularly review individuals who are using dental appliances for snoring. Mandibular advancement splints (mandibular repositioning splints) push the lower jaw forwards. The tongue has muscular connections to the mandible and therefore is pulled forwards at the same time, which prevents obstruction of the airway at the oropharynx. This is a similar mechanism to the jaw-thrust maneuver used to maintain patency of a supine patient in first aid. In addition, mandibular advancement splints increase the tension in the soft palate and pharyngeal walls. Mandibular advancement splints are used for snoring and for mild to moderate obstructive sleep apnea. They may be useful for people with retrognathia (receded lower jaw). Mandibular advancement splints are better tolerated than CPAP. They can reduce snoring loudness and improve quality of life of snorers and their sleeping partners. Tongue repositioning (retaining) devices are made of soft acrylic and cover the upper and lower teeth and create a seal with the lips. They have a "bulb" or "bubble" which sticks out the front of the mouth. This creates negative suction pressure, holding the tongue in a forward position and increasing the airway space behind the tongue. Soft-palate lifters are devices which lift the soft palate. They are useful for people who have weak muscles in the region. Orthodontic treatment Orthodontic treatment may improve some dental problems associated with snoring, such as a narrow palate. Positive airway pressure Continuous positive airway pressure (CPAP) is a machine which pumps air through a flexible hose to a mask worn over the mouth, nose, or both. The pressure of the air keeps the airway open. CPAP is considered the gold standard treatment for obstructive sleep apnea. It has been shown to reduce snoring associated with obstructive sleep apnea. However, CPAP can be uncomfortable, and many people stop using it. This is especially true for primary snoring. Surgery Surgical procedures outside the nose and soft palate for treatment of primary snoring have been discouraged. Many different surgical procedures have been used for snoring, including: • Nasal surgeries, e.g. septoplasty, turbinoplasty, various procedures for nasal valve collapse (spreader grafts, spreader flaps, butterfly grafts, batten grafts). • Palatal surgeries, e.g. uvulopalatopharyngoplasty (most commonly performed procedure for snoring), palatal implants (pillar procedure), somnoplasty (may combine other sites) • Adenoidectomy or tonsillectomy (or combined, termed adenotonsillectomy). • Tongue base surgeries • Hypopharyngeal surgery • Orthognathic surgery, e.g. maxillary mandibular advancement • Hypoglossal nerve stimulation • Tracheostomy • Bariatric surgery ==Epidemiology==

Snoring is one of the most common sleep disorders. Occasional snoring is almost universally present in humans. Habitual (primary snoring) is less common but still a common problem. ==Society and culture==

There are descriptions of snoring in the fifteenth century. CPAP was first used for snoring and obstructive sleep apnea in 1981. == References ==