It also estimated that in middle-age as many as 9% of women and 24% of men were affected, undiagnosed and untreated.The costs of untreated sleep apnea reach further than just health issues. It is estimated that in the U.S., the average untreated sleep apnea patients annual health care costs $1,336 more than an individual without sleep apnea. This may cause $3.4 billion/year in additional medical costs. Whether medical cost savings occur with treatment of sleep apnea remains to be determined. Frequency and population
Sleep disorders including sleep apnea have been become an important health issue in the United States. Twenty-two million Americans have been estimated to have sleep apnea, with 80% of moderate and severe OSA cases undiagnosed.OSA can occur at any age, but it happens more frequently in men who are over 40 and overweight. History
A type of CSA was described in the German myth of Ondines curse where the person when asleep would forget to breathe. The clinical picture of this condition has long been recognized as a character trait, without an understanding of the disease process. The term "Pickwickian syndrome" that is sometimes used for the syndrome was coined by the famous early 20th-century physician William Osler, who must have been a reader of Charles Dickens.
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
strokeHigh 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. Complication
It is considered that OSA is a serious medical condition. Daytime fatigue and sleepiness, cardiovascular problems and eye problems are also be considered as a potential complications of OSA. OSA may also be a risk factor of COVID-19. It is found that 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.