Obstructive sleep apnea (OSA) is a form of sleep-disordered breathing that is characterized by frequent episodes of snoring and a cessation in breathing for greater than 10 seconds, resulting in disrupted sleep. OSA results from decreased motor tone of either the tongue or airway dilator muscles, causing complete or partial obstruction of the upper airway during sleep. Patients with OSA frequently suffer from daytime sleepiness and reduced quality of life, as well as cardiac, metabolic, and psychiatric disorders. Obesity is the primary risk factor and contributes to the other disorders commonly diagnosed in this population.
Symptoms and Diagnosis
Untreated OSA is an independent risk factor for increased comorbidities, making it imperative to evaluate common signs and symptoms such as disruptive snoring, daytime sleepiness, obesity, and large neck circumference (>42 cm in men). Diagnostic criteria for OSA include either an apnea-hypopnea index (AHI) of greater than five events per hour plus symptoms of excessive daytime sleepiness or an AHI greater than 15 events per hour regardless of symptoms.
OSA is independently associated with disorders of the cardiovascular, endocrine, and central nervous systems. A study by Peppard et al examined the association between OSA and hypertension. The investigators found OSA to be an independent risk factor for hypertension, and that treatment with continuous positive airway pressure (CPAP) improved blood pressure. A prospective study by Marin et al found that untreated OSA increased the odds by 2.87 for a fatal and 3.17 for a nonfatal cardiovascular event. Studies have found a relationship between OSA and increased incidence of stroke (hazard ratio 2.86–3.56) and a prevalence of seizures in 10% to 45% in patients with OSA.[7,8] Central nervous system (CNS) disorders result from the fatigue and hypersomnolence associated with OSA. Patients with OSA frequently develop insulin resistance that leads to a diagnosis of diabetes. Studies have confirmed that patients with moderate-to-severe OSA are likely to have an elevated fasting glucose level and 2-hour glucose tolerance.[9,10]
Current treatment options for OSA include both non-pharmacologic and pharmacologic modalities (Table 1). CPAP is the treatment of choice, eliminating episodes of apnea and hypopnea by maintaining airway patency and creating a pneumatic splint.[11,12] Patient compliance with CPAP is estimated at 40% to 60% secondary to the cumbersome equipment required for therapy. Alternative therapies include weight loss, oral appliances, surgery, and drug treatment. Treatment goals include reducing risk factors for OSA, correcting underlying metabolic disorders, treating the consequences, and preventing episodes of apnea and hypopnea.
It is thought that tricyclic antidepressants (TCAs) improve OSA by increasing rapid eye-movement (REM) sleep latency while decreasing the overall amount of time spent in REM sleep. This modification to sleep architecture possibly improves OSA since the condition worsens during REM sleep, especially in overweight patients.
The selective serotonin reuptake inhibitors (SSRIs) are thought to increase upper airway muscle tone in addition to increasing the amount of serotonin in the brain, which can improve sleep apnea by stimulating the hypoglossal motoneurons.
In addition to respiratory stimulation, nicotine can possibly improve OSA by increasing the activity of muscles that dilate the upper airway.
Although methylxanthine derivatives are also respiratory stimulants, these agents work by blocking adenosine receptors and stimulating ventilatory drive.
Inhaled nasal corticosteroids can be used to improve airway patency. (more…)