Sleep apnea is a common and potentially serious sleep disorder in which breathing repeatedly stops and starts during sleep. These pauses in breathing, known as apneas, can last from a few seconds to more than a minute and may occur dozens or even hundreds of times per night, significantly disrupting sleep quality and reducing oxygen levels in the blood. There are three main types of sleep apnea. Obstructive sleep apnea (OSA) is by far the most common and occurs when the muscles in the throat relax during sleep, causing the airway to narrow or close completely. Central sleep apnea is less common and occurs when the brain fails to send the proper signals to the muscles that control breathing. Complex (or mixed) sleep apnea is a combination of both types. Common symptoms of sleep apnea include loud snoring, gasping or choking during sleep, excessive daytime sleepiness, morning headaches, difficulty concentrating, irritability, and frequent nighttime urination. Many people are unaware they have sleep apnea and are alerted to it by a bed partner who notices their snoring or pauses in breathing. If left untreated, sleep apnea can increase the risk of high blood pressure, heart disease, stroke, type 2 diabetes, and other serious health conditions. It is also a significant contributor to drowsy driving and accidents. Diagnosis is made through a sleep study (polysomnography), which can be conducted in a sleep laboratory or at home. The most effective and widely used treatment for obstructive sleep apnea is CPAP (continuous positive airway pressure) therapy. Other options include oral appliances, lifestyle modifications such as weight loss, positional therapy, and in some cases surgery.