Sleep apnea is a common disorder that is characterized by a marked reduction or even absence of airflow at the mouth or nose during sleep due to increased collapsibility of the airway. Apnea occurs in episodes that result in a reduction of oxygen reaching the brain, and they are typically terminated by minor arousals. Patients with apnea usually present with snoring and/or excessive daytime sleepiness typically while watching TV, talking or – in advanced case – driving. Bed partners often witness the patient’s apnea and report it.
A number of factors are known to increase the risk for sleep apnea. They include:
Sleep apnea is more common in the elderly. The prevalence of apnea in the elder people (more than 65 years) is two-fold greater than the young. This is explained by many factors, the most important of which are the age-related decrease in the size and shape of the upper airway lumen and the increase in pharyngeal resistance.
2. Male sex:
Males are more liable to develop sleep apnea than females. In general population, the male to female ratio of sleep apnea is two to one. This gender difference is attributed to multiple factors including hormonal changes, differences in pharyngeal collapsibility and central respiratory drive. However, females are liable to develop sleep apnea during pregnancy due to obstruction of the upper airway.
Obesity is considered a major risk factor for sleep apnea. It is estimated that about 70% of sleep apnea patients are obese. Fat deposition in the neck and the resulting increased neck circumference cause obstruction of the upper airway and apnea. Typical sleep apnea patients are obese with short thick neck. Some studies indicate that the neck circumference is more predictive of sleep apnea than the body mass index.
4. Family history:
Different studies showed that the first-degree relatives of patients with sleep apnea are more vulnerable to develop the disorder than those with no family history. It was also found that the number of affected relatives is directly correlated with the susceptibility of an individual to develop the disorder.
5. Craniofacial abnormalities:
Over the last the decades, abnormalities in the skull and face were stablished to have an important role is the development of sleep apnea. The most abnormalities identified were smaller mandibles, a narrowed posterior buccal air space, a greater flexion of the skull base and an elongated soft palate. Those abnormalities when present – especially if associated with obesity – cause narrowing of the upper air way and cessation of breathing during sleep.
Smoking irritates the airway resulting in edema and narrowing, thereby predisposing to sleep apnea. Studies showed that smokers are 2.5 times more liable to develop sleep apnea than non-smokers.
7. Alcohol consumption:
When taken close to bed time, alcohol relaxes the upper airway muscles increasing its collapsibility and resulting in apnea. Moreover, alcohol can prolong the duration of sleep apnea resulting in more compromise to the oxygen flow to the brain, thereby worsening the complications of apnea.
8. Medical conditions:
Certain medical conditions are associated with sleep apnea. For instance:
- Cerebrovascular stroke: sleep apnea is prevalent in ischemic stroke patients. In some studies, more than 70% of ischemic stroke patients have sleep apnea. Sleep apnea is an independent risk factor for ischemic stroke and it has a negative impact on the prognosis and long-term outcome of stroke.
- Congestive heart failure: sleep apnea is prevalent in patients with heart failure. Several studies showed that more than 50% of patients with heart failure suffer from sleep apnea.
- Ischemic heart disease: Significant sleep apnea was found in about 30-50% of patients with ischemic heart disease. Patients in acute exacerbations of their cardiac condition were found to have more severe forms of apnea.
- Acromegaly: About 70% of patients with acromegaly suffer sleep apnea. The enlarged tongue and pharyngeal soft tissue are responsible for obstruction of the airway during sleep.
- Diabetes Mellitus: Sleep apnea is highly prevalent in diabetic patients. It is estimated that about 50-80% of diabetic patients suffer from sleep apnea. Sleep apnea is thought to be a consequence of the altered respiratory function caused by diabetic neuropathy, and the disrupted sleep architecture caused by apnea can cause alteration of blood glucose level and consequently diabetes Mellitus.
- Hypothyroidism: About 25-30% of patients with hypothyroidism have sleep apnea, and this number is increased to up to 90% in patients with myxedema. The enlarged thyroid gland along with the hypothyroidism weakened muscles are thought to be the responsible mechanisms for sleep apnea.
- Cushing syndrome: Weight gain in Cushing patients, fat deposition around the neck, face, trunk and the weak respiratory muscles are responsible for the high prevalence (around 25%) of sleep apnea among those patients.