<P> The surgical treatment for velopalatal insufficiency may cause obstructive sleep apnea syndrome . When velopalatal insufficiency is present, air leaks into the nasopharynx even when the soft palate should close off the nose . A simple test for this condition can be made by placing a tiny mirror on the nose, and asking the subject to say "P". This p sound, a plosive, is normally produced with the nasal airway closes off - all air comes out of the pursed lips, none from the nose . If it is impossible to say the sound without fogging a nasal mirror, there is an air leak - reasonable evidence of poor palatal closure . Speech is often unclear due to inability to pronounce certain sounds . One of the surgical treatments for velopalatal insufficiency involves tailoring the tissue from the back of the throat and using it to purposefully cause partial obstruction of the opening of the nasopharynx . This may actually cause OSA syndrome in susceptible individuals, particularly in the days following surgery, when swelling occurs (see below: Special Situation: Anesthesia and Surgery). </P> <P> Finally, patients with OSA are at an increased risk of many perioperative complications when they are present for surgery, even if the planned procedure is not on the head and neck . Guidelines intended to reduce the risk of perioperative complications have been published . </P> <P> The normal sleep / wake cycle in adults is divided into REM (rapid eye movement) sleep, non-REM (NREM) sleep, and consciousness . NREM sleep is further divided into Stages 1, 2 and 3 NREM sleep . The deepest stage (stage 3 of NREM) is required for the physically restorative effects of sleep, and in pre-adolescents, this is the period of release of human growth hormone . NREM stage 2 and REM, which combined are 70% of an average person's total sleep time, are more associated with mental recovery and maintenance . During REM sleep, in particular, muscle tone of the throat and neck, as well as the vast majority of all skeletal muscles, is almost completely attenuated, allowing the tongue and soft palate / oropharynx to relax, and in the case of sleep apnea, to impede the flow of air to a degree ranging from light snoring to complete collapse . In the cases where airflow is reduced to a degree where blood oxygen levels fall, or the physical exertion to breathe is too great, neurological mechanisms trigger a sudden interruption of sleep, called a neurological arousal . These arousals rarely result in complete awakening but can have a significant negative effect on the restorative quality of sleep . In significant cases of OSA, one consequence is sleep deprivation due to the repetitive disruption and recovery of sleep activity . This sleep interruption in stage 3 (also called slow - wave sleep), and in REM sleep, can interfere with normal growth patterns, healing, and immune response, especially in children and young adults . </P> <P> Diagnosis of OSA is often based on a combination of patient history and tests (lab - or home - based). These tests range, in decreasing order of cost, complexity and tethering of the patient (number and type of channels of data recorded), from lab - attended full polysomnography ("sleep study") down to single - channel home recording . In the USA, these categories are associated with insurance classification from Type I down to Type IV . Reimbursement rules vary among European countries . In a systematic review of published evidence, the United State Preventive Services Task Force in 2017 concluded that there was uncertainty about the accuracy or clinical utility of all potential screening tools for OSA, and recommended that current evidence is insufficient to assess the balance of benefits and harms of screening for OSA in asymptomatic adults . </P>

Increased risk of sleep apnea is caused by all of the following except