Obstructive Sleep Apnea Causes Make an Appointment Refer a Patient Ask a Question Reviewed by Sheila Tsai, MD (March 01, 2017) In obstructive sleep apnea (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, opening them enough for air to flow through again. This arousal is brief, and you often do not 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 weight or 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. But obesity is increasingly playing a greater role in childhood sleep apnea. Central sleep apnea, a much rarer condition, occurs when the brain intermittently fails to send the appropriate signals to the breathing muscles for respiration. Obstructive Sleep Apnea Symptoms Clinical Trials For more than 100 years, National Jewish Health has been committed to finding new treatments and cures for diseases. Search our clinical trials.