Sleep apnea is a serious, potentially life-threatening disorder. It occurs when the flow of air during breathing decreases or is completely blocked during sleep. It may be accompanied by a lack of oxygen and a disruption of deep sleep. People who have sleep apnea almost always snore heavily. More Information.

Although the exact cause is not known, narcolepsy appears to be a disorder of the part of the brain that controls sleep. Narcolepsy is a sleep disorder defined by constant sleepiness and a tendency to sleep at inappropriate times. More Information.

People with restless leg syndrome experience very unpleasant sensations that occur in the legs when they are sitting or lying still, especially at bedtime. The uncomfortable feeling of restless leg syndrome appears most often in the calves of the legs and affects a person's ability to sleep at night and causes excessive daytime sleepiness. More Information.

Insomnia can mean trouble falling asleep, trouble staying asleep, or sleep that is non-restorative. In about 10% of the population, insomnia has become chronic. Since insomnia is a symptom rather than a diagnosis, a careful sleep history, and sometimes an overnight sleep study, is required to determine the cause. More Information.