Snoring is defined as an acoustic phenomenon, predominantly inspiratory, of variable intensity, caused by the vibration of the soft tissues and which is based on oropharyngeal airflow resistance in the upper airway. Habitual snoring is a common phenomenon with a prevalence ranging between 4 and 29% in men and between 3 and 14% in women, which increases with age and is related to obesity. Although initially regarded as an anecdotal phenomenon without clinical relevance, many studies have linked snoring with various cardiovascular diseases including high blood pressure, heart disease and stroke, which means that today it is considered a pathological phenomenon.
Classification of snoring
Classifying snoring throws up a string of problems. The scientific literature contains distinctions between simple or benign snoring when it is isolated from any condition or disease which compromises the calibre of the UA and pathological snoring when it is associated with Sleep-Related Breathing Disorders. Lugaresi et al makes a distinction between continuous snoring and cyclical snoring. He defines continuous snoring as an inspiratory noise with a constant amplitude throughout each cycle. Continuous snoring has no detrimental effect on the health of the patient nor does it bother the sleeping partner. It is a common phenomenon but not pathological one. In contrast, cyclical snoring is characterized by a cyclical noise of variable intensity (up to 85 decibels), much louder than that of continuous snoring, followed by silent intervals which correspond to episodes of apnea.
The American Sleep Association (ASA) defines primary snoring as "severe respiratory sounds produced in the upper airways during sleep, without episodes of apnea, hypoventilation, desaturation or arousals and which show no evidence of insomnia or hypersomnia". Snoring is caused by the vibration of the soft tissues of the pharynx (soft palate, tonsils, lateral pharyngeal walls ...) usually occurring on inspiration. This vibration generates an annoying noise, although not pathological as it is not accompanied by sleep disruption, daytime sleepiness or desaturation. It can be a social nuisance for wedded couples or a condition that evolves into obstructive pathologies, for example, OSAHS. Snoring is considered non-pathological if the intensity of the noise is less than 40dB and the frequency is steady during sleep. Snoring is defined pathological when the noise is loud, irregular and laboured.
|130 dB||Airplane taking off|
|90 dB||Car horn|
|60-80 dB||Severe snoring|
|100 dB||Electric drill|
|70 dB||Intense traffic|
|50 dB||Moderate snoring|
|10 dB||The tick-tock of a clock|
|1 dB||A baby's respiration|
|0 dB||Auditory threshold|
Other classifications are based on sound recordings which measure the number of peaks of more than 55 decibels produced during a night. Less than 150 peaks are considered as non-snorers, between 150 and 300 peaks are considered mild snorers, between 300 and 500 are considered moderate snorers and if the peak exceeds 55dB on more than 500 occasions the snorer is considered severe. The World Health Organization (WHO) has established the maximum tolerable noise is approximately 65 dB. Studies on the acoustics of snoring have recorded values above 80dB in habitual snorers. When snoring exceeds 70 dB, it leads to awakenings in the snorers themselves, which impacts on sleep quality and therefore has secondary effects on the health of sleep partners who are continuously exposed to these intolerable noise levels. The sound of snoring is even more intense and annoying to sleep partners, given that it occurs in an quiet night-time environment.
Epidemiology of snoring
The prevalence of respiratory disorders is very high in today's society (25% in men and 11% in women) as various studies have shown in recent years. Approximately 45% of adults snore occasionally and 25% do so regularly. As a medical condition, snoring causes problems on two fronts. Firstly, the snorer may experience social problems, being considered an "unbearable" sleep companion and secondly, the patient may suffer more serious medical consequences as a result of snoring. The impact on personal relationships cannot be dismissed as sleep partners may have to endure a noise level of 80-90 dB (equivalent to the noise a truck makes at high speed on a motorway). The threshold that may cause hearing damage is estimated at an intensity of 65 dB. On the other hand, there have been cases of self -inflicted hearing loss due to the patients' own snoring. Keep in mind that sometimes snoring reaches the sound intensity of a chainsaw. Snoring disrupts personal and family relationships, causing psychological damage which extends to all those in close proximity, resulting in high rates of divorce.
Factors Contributing to Snoring
Snoring is common in adults and is not usually a sign of an underlying disorder. However, it is an indication of an increase in the resistance of the upper airway and may be a sign of Obstructive Sleep Apnea. Snoring may also be secondary to other morphological conditions which narrow the upper airway, such as obesity, nasal congestion, craniofacial abnormalities, hypothyroidism, acromegaly, and adenotonsillar hypertrophy. The pathogenic mechanisms of snoring are complex. It is a respiratory noise caused by the vibration of the walls of the oropharynx, when the permeability of the upper airway is altered by one of the many factors which regulate it. Snoring originates from the collapse of the upper airway at the level of the oropharynx.
- The importance of nasal breathing
Mouth breathing is a common condition that predisposes to habitual snoring. During normal nasal breathing, resistance is generally low in one nostril and higher in the other, allowing a balance of the respiratory cycle. When bilateral nasal obstruction exists the increase in resistance provokes a sleep arousal which restores the airflow through the mouth. This mouth breathing leads to increased resistance in the pharynx due to a reduction in calibre of the airway caused by the downward displacement of the suprahyoid structures. Snoring may also be related to a deviated nasal septum, an enlargement of the nasal turbinates, tonsils or palate, chronic laryngitis, low muscle tone of the mouth or throat, or temporary nasal obstruction. Any of these factors predispose to a reduction in pharyngeal calibre thus decreasing the quantity of air reaching the lungs and giving rise to the vibrating sound which causes snoring.
Is the most important factor in Sleep-Related Breathing Disorders. Being overweight directly affects the size of the upper airway and may coexist alongside metabolic and endocrine problems associated with obese patients.
- Postural factors
The supine position increases the likelihood of snoring by causing the downward displacement of the mandibular structures.
- The ingestion of alcohol and sedatives
Makes snoring and OSAHS more likely due to their depressant effects on the respiratory centre.
Also favours the presence of snoring as it causes inflammation and oedema which in turn can cause cause pharyngeal narrowing.
There is a greater prevalence of snoring in men than in women. The reason for this difference is not yet clear but may be due to the influence of sex hormones and anthropometric factors. Currently there is no conclusive evidence to justify why males are dominant in the development of snoring. What has been demonstrated is that the hormone progesterone (typically female) helps breathing and snoring has been improved when pharmacologically produce progesterone is administered. The female is hormonally protected from snoring, but that may change with pregnancy due to an increase in the progesterone levels which also causes nasal congestion. Similarly, in post-menopausal women ,when the progesterone level declines, there is a justified rise in the prevalence of snoring.
All epidemiological studies show that the prevalence of snoring increases with age. About 20% of middle aged adults are snorers. This percentage varies when studied by age subgroups: 10% of men and 5% of women aged between 30 and 60 snore and 60% of men and 40% of women above age 60 snore. The age factor is instrumental in the development of snoring. In children the prevalence is fairly high (although lower than in adults) causing child snorers to suffer from behavioural problems and cognitive failures. At the 21st Congress of the Spanish Society of Paediatric Outpatients and Primary Care, Jordi Coromina noted that 12% of children snore and half of them have urinary incontinence while sleeping. In addition, sleep apnea triples the risk of attention deficit and hyperactivity. Moreover, studies show that children who snore can lose up to 11 points from their IQ and can see their school performance affected by fatigue and behavioural problems. Along the same lines, according to a report from the Central Hospital of the University of Helsinki, published in the Journal of Developmental and Behavioural Paediatrics, children who snore are more likely to have other sleep problems such as nightmares, somniloquy (sleep talking), difficulties going to bed and symptoms of depression and anxiety, as well as language and attention problems than others who don't snore.