may become intractable, leading to depression. There is evidence that the risk of diabetes among those with moderate or severe sleep apnea is higher. Finally, because there are many factors that could lead to some of the effects previously listed, some people are not aware that they have sleep apnea and are either misdiagnosed or ignore the symptoms altogether. Risk factors Sleep apnea can affect people regardless of sex, race, or age. However, risk factors include: being male obesity age over 40 large neck circumference (greater than 16–17 inches) enlarged tonsils or tongue narrow upper jaw nasal congestion allergies receding chin gastroesophageal reflux a family history of sleep apnea smoking Alcohol, sedatives and tranquilizers may also promote sleep apnea by relaxing throat muscles. People who smoke tobacco have sleep apnea at three times the rate of people who have never done so. Central sleep apnea is more often associated with any of the following risk factors: being male an age above 65 having heart disorders such as atrial fibrillation or atrial septal defects such as PFO stroke High blood pressure is very common in people with sleep apnea. Mechanism When breathing is paused, carbon dioxide builds up in the bloodstream. Chemoreceptors in the bloodstream note the high carbon dioxide levels. The brain is signaled to awaken the person, which clears the airway and allows breathing to resume. Breathing normally will restore oxygen levels and the person will fall asleep again. This carbon dioxide build-up may be due to the decrease of output of the brainstem regulating the chest wall or pharyngeal muscles, which causes the pharynx to collapse. People with sleep apnea experience reduced or no slow-wave sleep and spend less time in REM sleep. Complications OSA is a serious medical condition. Daytime fatigue and sleepiness, cardiovascular problems and eye problems are considered potential complications of OSA. OSA may also be a risk factor of COVID-19. People with OSA have a higher risk of developing severe complications of COVID-19. Diagnosis Despite this medical consensus, the variety of apneic events (e.g., hypopnea vs apnea, central vs obstructive), the variability of patients' physiologies, and the inherent shortcomings and variability of equipment and methods, this field is subject to debate. Within this context, the definition of an event depends on several factors (e.g., patient's age) and account for this variability through a multi-criteria decision rule described in several, sometimes conflicting, guidelines. Oximetry Oximetry,