There are some people who have problems with their sleep. Some have insomnia, narcolepsy, snoring, and some other have sleepwalking which is also known as somnambulism and noctambulism.
Circadian Rhythms Disorders and Sleep Phase Syndrome
Some people tend to sleep early and wake up early in the morning and some cannot sleep early and as a consequence, wakes up late. These and other sleep-related problems are manifestations of a malfunctioning biological circadian clock and characterize several forms of Circadian Rhythm Disorder.