Obstructive sleep apnea (OSA) is a condition where the walls of the throat relax and narrow during sleep, interrupting normal breathing.
There are two types of breathing interruption characteristic of OSA:
- apnea– where the muscles and soft tissues in the throat relax and collapse sufficiently to cause a total blockage of the airway; it is called an apnea when the airflow is blocked for 10 seconds or more
- hypopnea– a partial blockage of the airway that results in an airflow reduction of greater than 50% for 10 seconds or more
The term “obstructive” distinguishes OSA from rarer forms of sleep apnea, such as central sleep apnea, which is caused by the brain not sending signals to the breathing muscles during sleep.
In people with OSA the airway has narrowed as the result of a number of factors, including:
- being overweight or obese
- having a large neck
- taking medicines that have a sedative effect, such as sleeping tablets
- narrow airway, large tonsils, adenoids or tongue, or a small lower jaw
- smoking or drinking alcohol, particularly before going to sleep