Sleep apnea, also spelled sleep apnoea, is a sleep disorder where a person has 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. Because the disorder disrupts normal sleep, those affected may experience sleepiness or feel tired during the day. In children it may cause hyperactivity or problems in school. Sleep apnea may be either obstructive sleep apnea (OSA) in which breathing is interrupted by a blockage of air flow, central sleep apnea (CSA) in which regular unconscious breath simply stops, or a combination of the two. Obstructive (OSA) is the most common form. Risk factors for OSA include being overweight, a family history of the condition, allergies, a small breathing airway, and enlarged tonsils. Obese people are the most likely to procure this disease, as well as many other diseases, because they are obese. Some people with sleep apnea are unaware they have the condition. In many cases it is first observed by a family member. Sleep apnea is often diagnosed with an overnight sleep study. For a diagnosis of sleep apnea, more than five episodes per hour must occur. Treatment may include lifestyle changes, mouthpieces, breathing devices, and surgery. Lifestyle changes may include avoiding alcohol, losing weight, stopping smoking, and sleeping on one's side. Breathing devices include the use of a CPAP machine. Without treatment, sleep apnea may increase the risk of heart attack, stroke, diabetes, heart failure, irregular heartbeat, obesity, and motor vehicle collisions. OSA affects 1 to 6% of adults and 2% of children. It affects males about twice as often as females. While people at any age can be affected, it occurs most commonly among those 55 to 60 years old. CSA affects less than 1% of people. A type of CSA was described in the German myth of Ondine's curse where the person when asleep would forget to breathe.