In OSA, the upper air passage is narrowed or blocked during sleep by the tongue and other soft tissues. Many people with OSA are snorers. As soft tissues block the airway air cannot flow into the lungs, although efforts to breathe continue. Breathing stops for several seconds to over a minute, and levels of blood oxygen may drop during these episodes. Eventually, the brain wakes you up enough to tighten the muscles of the upper airways, openingthem enough for air to flow through again. This arousal is brief, and the person likely won't remember it. These repeated arousals decrease sleep quality, and people with sleep apnea often feel tired during the day.
Not all obstructive sleep apnea is caused by soft-tissue obstruction. The airway may also be narrowed by excessive body weightor may just be naturally more narrow, making it more likely to collapse.
In children, obstructive sleep apnea is often caused by enlarged tonsils or adenoids.
Central sleep apnea, a much rarer condition, occurs when the brain intermittently fails to send the appropriate signals to the breathing muscles for respiration.