The majority of sufferers of sleep apnea encounter either obstructive sleep apnea, which is actually a real blockage of the airway by tissue inside the throat, or central sleep apnea, which is the inability of the brain to control even respiration, leading to cycles of apneas (the periods without breathing)  and hyperpneas (periods of rapid respiration). If a patient is suffering from both central (CSA) and obstructive (OSA) sleep apnea and exhibits signs or symptoms of each, the individual is considered to suffer from "mixed sleep apnea". Mixed sleep apnea is a tricky form of sleep apnea which is quite tough to successfully treat with established forms of treatment.

Mixed sleep disease is typically diagnosed once the patient not only has physical blockage of the air passage, but also suffers from lowered or erratic neurological activity within the area that controls breathing. This can result in remedies which are employed to reduce OSA only are not effective in treating mixed sleep apnea.

Another symptom that regularly occurs in those suffering from both OSA and mixed sleep apnea is chronic coronary heart failure. Heart failure is a persistent symptom of OSA, and it also shows up frequently in mixed sleep apnea cases.

Those who use narcotics, besides all the other risks, also risk inducing mixed sleep apnea as well. Many narcotics and opiates lower repertory activity which can lead to cases of mixed sleep apnea, particularly if the user already experiences either OSA or CSA.

When a patient suffers from one type of sleep problem, the signs and symptoms are usually amplified once if the other kind shows up as well. Less daytime energy, pronounced lethargy, possibly a deteriorating heart condition, and fitful and restless sleep all become more pronounced. The individual's airway not only becomes blocked by soft tissue, but their brain does not signal an attmpt to breath when the blockage happens. In this event much greater stress is induced, especially in the neurological center responsible for respiration. This additional anxiety and stress acts negatively on the heart muscle and can cause damage over time. Also, the necessary rest period is interrupted by the fight to draw a breath. Because the brain and body can't complete a regular sleep cycle, signs of sleep deprivation will start to become apparent. For example, both the ability to concentrate and learn new tasks will become much harder.