Sleep disorders involve any difficulties related to sleeping, including difficulty falling or staying asleep, falling asleep at inappropriate times, excessive total sleep time, or abnormal behaviors associated with sleep.
Causes, incidence, and risk factors
More than 100 different disorders of sleeping and waking have been identified. They can be grouped in four main categories:
Problems with falling and staying asleep (insomnia)
Problems with staying awake (excessive daytime sleepiness)
Problems with sticking to a regular sleep schedule (sleep rhythm problem)
Unusual behavoirs during sleep (sleep-disruptive behaviors)
PROBLEMS WITH FALLING AND STAYING ASLEEP
Insomnia includes any combination of difficulty with falling asleep, staying asleep, intermittent wakefulness and early-morning awakening. Episodes may come and go (be transient), last as long as 2 to 3 weeks (be short-term), or be long-lasting (chronic).
Poor sleeping environment such as excessive noise or light
Caffeine
Alcohol or other drugs
Use of certain medications
Heavy smoking
Physical discomfort
Daytime napping
Counterproductive sleep habits:
Early bedtimes
Excessive time spent awake in bed
Disorders include:
Psychophysiological insomnia: a condition in which stress caused by the insomnia makes it even harder to fall asleep
Delayed sleep phase syndrome: your internal clock is constantly out of synch with the "accepted" day / night phases; for example, patients feel best if they can sleep from 4AM to noon
Hypnotic-dependent sleep disorder: insomnia that occurs when you stop or become tolerant to certain types of sleep medications
Stimulant-dependent sleep disorder: insomnia that occurs when you stop or become dependent on certain types of stimulants
PROBLEMS WITH STAYING AWAKE
Disorders of excessive sleepiness are called hypersomnias. These include:
Problems may also occur when you do not maintain a consistent sleep and wake schedule. This occurs when traveling between times zones and with shift workers on rotating schedules, particularly nighttime workers.