Poor breathing during sleep a] reduces oxygen available for metabolism and may therefore depress basal metabolic rate during sleep, increasing the difference between supply of food energy and demand for it during that time and thereby promoting weight gain, and b] reduces sleep quality and recovery per time unit of sleep, resulting in sleepiness or fatigue that may prompt affected people to eat more in an attempt to increase short-term energy levels. Correlation with cardiac disorders:Atrial fibrillation (AF): A study in the medical journal Sleep found that the prevalence of atrial fibrillation among patients with idiopathic central sleep apnea was significantly higher than the prevalence among patients with obstructive sleep apnea or no sleep apnea (27%, 1.7%, and 3.3%, respectively). The study was based on 180 subjects with 60 people in each of the 3 groups. Possible explanations for the association between CSA and AF include a causal relationship in one direction or the other between the two conditions or a common cause involving an abnormality of central cardiorespiratory regulation. Adults with congestive heart failure are at risk for a form of central apnea called Cheyne-Stokes respiration, which manifests itself both during sleep and during waking hours. Cheyne-Stokes respiration is characterized by periodic breathing featuring recurrent episodes of apnea alternating with episodes of rapid breathing. There is good evidence that replacement of the failing heart (heart transplant) cures central apnea in these patients.
Central sleep apnea (CSA) or central sleep apnea syndrome (CSAS) is a  sleep-related disorder in which the effort to breathe is diminished or absent, typically for 10 to 30 seconds either intermittently or in cycles, and is usually associated with a reduction in blood oxygen saturation. CSA is usually due to an instability in the bodys feedback mechanisms that  control respiration. Central sleep apnea can also be an indicator of Arnold–Chiari malformation. Signs and symptoms
In a healthy person during sleep, breathing is regular so oxygen levels and carbon dioxide levels in the bloodstream stay fairly constant:  After exhalation, the blood level of oxygen decreases and that of carbon dioxide increases. Exchange of gases with a lungful of fresh air is necessary to replenish oxygen and rid the bloodstream of built-up carbon dioxide. Oxygen and carbon dioxide receptors in the body (called chemoreceptors) send nerve impulses to the brain, which then signals for reflexive opening of the larynx (enlarging the opening between the vocal cords) and movements of the rib cage muscles and diaphragm. These muscles expand the thorax (chest cavity) so that a partial vacuum is made within the lungs and air rushes in to fill it.