The most common sleep disorder is insomnia. Too-early awakening and not being able to get back to sleep is often associated with grief. There are all sorts of remedies for insomnia, including drugs, but reading a boring book can help many people. It also helps to understand that if there is a tendency toward insomnia, the person should never have cola drinks, coffee, or tea with dinner. Chocolate is another culprit.
Sleep apnea is less common than insomnia, but it is much more dangerous.
The sleeper with apnea stops breathing for a period of time. If this happens many times during the night, the apnea patient winds up chronically exhausted. In the less severe form of apnea, there are breathing difficulties associated with loud and obnoxious snoring, but the person is not tired the next day. Surgery and positive air-flow devices can help the person with apnea. Narcolepsy is the most unusual sleep disorder.