Obstructive sleep apnea (OSA) is a condition where the airway is temporarily blocked so that breathing is repeatedly stopped and started during sleep. A common cause of OSA is that the airway becomes blocked due to the excessive relaxation of your throat muscles. For medics, this is generally due to narrowing of the velopharynx. While OSA almost always results in snoring, the reverse is not so. You can snore without blocking the airway.