Obstructive Sleep Apnea: Definition, Causes, and Risk Factors – Sleep is a complex physiological process consisting of stage 1–4 called non rapid eye movement sleep (NREM) and stage 5 called rapid eye movement sleep (REM). More than half of total sleep is the stage NREM while 20–35% are REM stage.
Many studies study sleep physiology and sleep disorders, such as obstructive sleep apnea (OSA) and central sleep apnea (CSA). It turns out that 95% of sleep breath disorders are upper airway obstructions and 5% are central nervous system disorders.
Breathing disorders during sleep can increase morbidity and mortality.
In America approximately 12 million people aged 30–60 suffer from OSA and every year 38,000 die from cardiovascular disease related to sleep-related respiratory disorders.
About 40–50% of congestive heart failure sufferers suffer from OSA or Cheyne–Stokes breathing with CSA. This disorder leads to progressive heart failure and a poor prognosis.
Obstructive Sleep Apnea Definition
Obstructive sleep apnea is a common form of apnea, which is defined as the stopping of breath during sleep.
Muscles in the body become relaxed during sleep. However, if the muscles at the back of the throat are too relaxed and then deflated, they will block the air entering the lungs causing oxygen deprivation. When the brain feels the body lacks oxygen, this will make your body gasp and breathe air, which then wakes you up and gets you to breathe normally.
Some people may experience this condition only once or twice a night. This condition is referred to as sleep apnea. Others may experience it many times, causing them to become sleep deprived and feel tired in the morning. This is called obstructive sleep apnea.
Obstructive sleep apnea makes the organs in your body lack the oxygen needed, which cause complications such as irregular heartbeat rhythms. However, with proper treatment, these complications can be avoided.
Obstructive Sleep Apnea Causes
Obstructive sleep apnea or OSA is a condition that occurs when the muscles at the back of the throat are too relaxed to block normal respiratory system processes. These muscles support the structure of the mouth, including the back of the roof of the mouth, pieces of triangular tissue that hang from the roof of the mouth (uvula), tonsils, and tongue.
In obstructive sleep apnea, when partial or complete air blocking occurs, oxygen levels in the blood may decrease due to respiratory cessation (10-20 seconds). It can also lead to a build-up of carbon dioxide.
Lack of oxygen causes your brain to panic and wake the body to breathe again. This sleep disorder is usually a very short thing, so you may not remember it.
You can wake up with shortness of breath that corrects breathing. You can make a snorting, choking, or panting sound.
Obstructive Sleep Apnea Risk Factors
About 80% of OSAS patients are obese. Obesity is one of the predisposing factors for the occurrence of OSAS. There is a close relationship between body mass index and OSAS events. A 10% increase in weight, increases AHI by 32% and increases the incidence of OSAS by 6 times. While weight loss of 10% can lead to a decrease in AHI 26%.
Obesity reduces the upper airway narrowing due to excessive accumulation of fatty tissue in the pharynx. While there is a close relationship between obesity and OSAS, it is important to note that not all subjects with obesity have OSAS.
Some studies show a high prevalence of OSAS in old age. Research conducted by Sleep Heart Health Study shows that 25% of men and 11% of women have a high AHI in the 40-98 age group. The peak age of patients diagnosed with OSAS for the first time in general is at the age of 50 years.
However, the relationship between age and OSAS is still controversial due to the many factors and other diseases that underlie the occurrence of OSAS.
Some epidemiological studies report OSAS is more common in men than women. In addition, there are several hypotheses that explain the relationship of gender with the onset of OSAS, among others, due to hormonal effects that can affect the upper airway musculature, differences in fat distribution and differences in the structure and function of the pharynx.
Size of neck circumference
The size of the neck circumference is a strong predictor and is one of the characteristics of physical examination in patients with OSAS. The circumference of the neck is the size of the neck that crosses the upper boundary of the cricothyroid membrane as measured in a standing position.
The study reported that the average size of neck circumference in OSAS patients was 43.7 cm while in non-OSAS patients it was 39.6 cm. Other studies have reported that the size of the neck circumference (>42.5 cm) is associated with an increase in AHI.
Abnormalities of upper airway structure
Some studies have shown that there are anatomical structural abnormalities in the craniofacial that have an impact on the narrowing of the upper airways. In general, there are abnormalities in the mandible, maxilla, and hyoid bone.
Small mandibular (micrognathia) and retrognathia are risk factors for the onset of OSAS. Micrognathia and retrognathia will cause the palatum mole, tongue and soft tissues around the pharynx to be pushed into the posterior so that the airways will narrow.
In addition, the overly posterior maxillary position can also be a risk factor for OSAS. This occurs because the palatum durum and soft tissue around the pharynx are pushed into the posterior so that the size of the lumen of the airways shrinks.
Abnormalities in the hyoid bone can cause the occurrence of OSAS. Hyoids that are too inferior will cause the tongue to be attracted to the posterior because the hyoid becomes one of the insersio of the tongue-forming muscles. Abnormalities in the tonsils, which are one of the lymphoid tissues in the upper airway can cause OSAS. Tonsil hypertrophy can cause OSAS especially in children.