SLEEP- RELATED BREATHING DISORDERS (SRBDs)
The most important cause of sleep disruption is sleep-disordered breathing. The term "sleep-disordered breathing" prima rily refers to the sleep apnea syndromes, but also includes disorders that result in noc turnal hypoventilation and hypoxemia such as restrictive and parenchymal pulmonaty diseases. While well known to cause exces sive daytime sleepiness, the sleep apnea syn dromes, both central and obstructive, are also important contributors to difficulty initiating and maintaining sleep because of frequent nocturnal arousals. Current defi nitions that have the most widespread clini cal use are based on guidelines provided by the Center for Medicare and Medicaid Services (CMS);2