Overview of Sleep Apnea

Sleep Apnea Facts & Figures

  • 20% of the adult population is estimated to suffer from mild-to-severe obstructive sleep apnea, which is the most prevalent form of sleep-disordered breathing.1
  • As the incidence of obesity increases, the number of patients suffering from sleep apnea is expected to increase.
  • More than 50% of patients with type 2 diabetes have sleep apnea.2
  • Up to 90% of patients with sleep apnea remain undiagnosed.3 Go to Risk Factors & Symptoms for information on recognizing obstructive sleep apnea.
  • Patients with untreated sleep apnea are at increased risk of having a traffic accident.4,5

Defining Sleep Apnea

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In patients with obstructive sleep apnea, the soft tissues in the upper airway relax during sleep and block the flow of air. Respiratory effort continues during the event.

  • An apnea is a complete occlusion of the airway and subsequent cessation of airflow for at least ten seconds.
  • Patients who suffer from apneas also tend to exhibit hypopneas, a partial occlusion of the airway that results in a 25-50% reduction in airflow.
  • Both apneas and hypopneas lead to oxygen desaturation and intermittent hypoxia.
  • Sleep apnea is classified as mild, moderate, or severe based on the number of apneas and hypopneas per hour (the “apnea-hypopnea index,” or AHI).

Physiological Effects of Sleep Apnea
When the body senses the imbalance between oxygen and carbon dioxide levels that results from cessation of breathing, the sympathetic system is activated. Breathing resumes when the patient has a brief arousal event due to the ensuing increase in systemic adrenaline.

The patient may not be aware of these cycles of apneas and arousals, although they can occur hundreds of times each night. Because the arousals are typically accompanied by loud gasps or snorts as the body struggles to restore airflow, the bed partner is often the one who witnesses (and is kept awake by) the apnea events and encourages the patient to seek treatment.

Classification of Sleep Apnea

AHI Scale Rev (AHIscale_500_pixels_wide.jpg)

Physiological Effects of Obstructive Sleep Apnea

During Apnea At the End of Apnea
Oxygen levels begin to decrease Oxygen levels begin to recover upon arousal
Heart rate slows Dramatic increase in heart rate
Blood pressure drops Dramatic increase in blood pressure


Sleep apnea has been linked with increased risks of many other medical conditions, including:

1 Young T. et al. Am J Respir Crit Care Med 2002; 165:1217-39
2 Einhorn D, et al. Endocrine Pract 2007;13:355-62
3 Young T, et al. Sleep 1997;20:705-6
4 Teran-Santos J, et al. N Engl J Med 1999;340 :881-3
5 Horstmann S, et al. Sleep 2000;23:383-9