Sleep apnea, also spelled sleep apnoea, is a sleep disorder characterized by pauses in breathing or periods of shallow breathing during sleep. Each pause can last for a few seconds to a few minutes and they happen many times a night. In the most common form, this follows loud snoring. There may be a choking or snorting sound as breathing resumes. As the disorder disrupts normal sleep, those affected may experience sleepiness or feel tired during the day. In children it may cause problems in school, or hyperactivity.There are three forms of sleep apnea: obstructive (OSA), central (CSA), and a combination of the two called mixed. OSA is the most common form.