Another option is continuous positive airway pressure, which involves wearing a mask over the nose and mouth during sleep; this treatment keeps the airway open by forcing air into the nasal passages. A different type of sleep apnea, called central sleep apnea, is believed to be caused by an abnormality in the brain's regulation of breathing during sleep.
Regardless of type, the individual with sleep apnea is rarely aware of having difficulty breathing, even upon awakening. Sleep apnea is recognized as a problem by others witnessing the individual during episodes or is suspected because of its effects on the body (sequelae). Symptoms may be present for years, even decades without identification, during which time the sufferer may become conditioned to the daytime sleepiness and fatigue associated with significant levels of sleep disturbance. The definitive diagnosis of sleep apnea is made by polysomnography.