Why do humans have such a big snoring/sleep apnea issue?
Contrary to popular belief, the throat and the upper airway has major impact on one’s sleep pattern and quality. The patency and size of one’s upper airway can affect the sleep quality and affect one’s health and quality of life. Due to a narrowed and/or congested throat (airway), the resistance to breathing can be very high, making breathing during sleep very difficult and laboured. This is more pronouced during sleep, as one’s muscles are completely relaxed and flaccid (soft), resulting in collapse and closure of the throat; hence, no breathing during sleep. This is known as Obstructive Sleep Apnea (OSA).
In Singapore, the incidence of Obstructive Sleep Apnea is estimated to be about 15%.
The evolution of the airway
It is well accepted that for most mammals, the airway is the most important conduit for the passage of air into the lungs, for gaseous exchange and the intake of oxygen. From the four-legged crawling canines to the two-legged standing gorillas, the airway is structurally within the cranio-facial skeleton (solid hard box/skull) of the animal.
Based on Darwin’s theory of evolution, it is well known that as the four-legged animal evolved and stood up, many changes took place in the upper body, namely, his upper limbs (arms/hands) got shorter, the spine became stronger, firmer and upright, the brain evolved bigger and, most crucially, the facial shape also changed.
Darwin's Theory of Evolution
The face shaped changed and became shorter from front to back, the face grew longer, the upper head expanded (as the brain grew bigger), and his neck development also increased, the neck gradually grew longer, with the airway conduit no longer being protected by the cranio-facial skeleton.
The evolutionary changes are evident when examining the cross sections of the canine model, to the gorilla model to the human model. The facial morphology has changed to shorten the cranio-facial section of the airway in the skull, enlarge the cranium (brain), increase neck length and with most of the airway unprotected in the neck.
(L-R): Canine section, gorilla section, human section
The unprotected airway in the neck is no longer protected by the cranio-facial skeleton, it is surrounded by skin, muscles and soft tissues; the airway is hence, more vulnerable, prone to collapse, injury and trauma.
This therefore leads to a much higher incidence of snoring and obstructive sleep apnea in humans compared to animals.
The airway
The nose
God gave us the nose to breathe through it, warm the air we breathe, and filter dust particles. The nose is pivotal in the breathing apparatus of the human. Any swelling/obstruction in the nose would result in turbulent airflow and difficulty breathing; resulting in more negative pressure required to inhale air into the lungs, this results in a more negative pressure in the throat (creating a vacuum effect), causing collapse of the throat muscles and structures.
Hence, the nose is pivotal in the management of obstructive sleep apnea, however, numerous studies/research have shown that OSA is disorder of a multilevel system in the throat (including the palate, the tonsils and/or the tongue) that collapses during sleep. Therefore, treating the nose alone is inadequate in the treatment of OSA.
The throat
The throat in the airway comprises of the palate (soft tissue structure containing mainly muscles), the side walls of the throat (mainly muscles and fat), the left and right tonsils (mainly lymphoid tissue), and the tongue. The throat is a dynamic structure that “acts” as a soft air conduit, to channel air into the lungs from the external environment. Any enlarged or swollen structure/s in this air conduit would narrow the space and result in obstruction during breathing. In the same vein, any form of negative pressure or vacuum effect would “suck” the structures inward and result in airway obstruction. With turbulent airflow in this soft air conduit, vibration ensues resulting in snoring. Snoring implies an increased resistance to the inflow of air during breathing at the level of the upper airways.
Some patients may have adeno-tonsillar hypertrophy with a crowded upper airway with very little space for airflow, while obese patients frequently have a thick and fatty soft palate and side walls in the throat. It is the vibration of these soft tissues during sleep that results in snoring.
The vibration causes snoring and it is the collapse of the upper airway that leads to obstructive sleep apnea. This leads to low oxygen at night while asleep and stress on the heart, lungs and brain, which may in turn lead to high blood pressure, stroke, heart attacks and sudden death.
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