Most people spend about one-third of their lives asleep. That's about seven or eight hours per night. Almost everyone has experienced temporary sleep problems caused by stress, physical conditions or other factors. Without adequate sleep, people feel less alert and energetic - lack of sleep can even affect mental and social functioning.

People sometimes develop sleep disorders, unexplained problems with sleep that last over a significant period of time. Such disorders can have a significant impact on quality of life. Some of the most common sleep disorders are:

• Sleep apnea
• Narcolepsy
• Restless legs syndrome
• Sleepwalking
• Nightmares and night terrors
• Insomnia

Sleep apnea

Sleep apnea is a sleep disorder in which the sleeper stops breathing for periods of up to two minutes, caused by obstructions to the movement of air in the upper respiratory passages. These obstructions occur when the muscles in the throat relax and collapse in on themselves as the sleeper reaches deeper levels of sleep. The person then stops breathing, wakes up to a lighter level of sleep and begins breathing again. The cycle keeps the person from ever reaching the deeper levels of sleep. Generally, the patient doesn't remember these breathing interruptions and feels tired and unrefreshed after waking up, even though he or she may have slept through the entire night.

Sleep apnea is a potentially life-threatening condition that can cause or contribute to heart attacks, strokes, impotence, high blood pressure and heart disease. More than half of all people with sleep apnea are first diagnosed at age 40 or older, and men are more likely to develop the disorder. Extremely overweight people have a greater risk of developing apnea also.

Common symptoms:

• Excessive, unexplained tiredness during the day
• Loud snoring
• Morning headache
• Episodes of obstructed breathing during sleep (often noticed by a bed partner)

Treatment options:

• Behavioral changes, including sleeping on the side, losing weight and avoiding alcoholic beverages.
• Dental appliances that bring the jaw forward, elevate the soft palate or keep the tongue from falling back and blocking breathing passages.
• Use of a C-PAP (continuous positive airway pressure) - a machine that blows air through a mask into your nose, helping keep airways open and unobstructed.
• For more serious sleep apnea problems, surgery may be recommended.

Narcolepsy

Everyone has had the experience of falling asleep during the day at an inappropriate time - during a dull lecture, for example. Usually, these experiences are normal, caused by a lack of sleep. However, people who generally get enough rest but often fall asleep at inappropriate times may be suffering from narcolepsy.

Because the disorder's severity can vary, not everyone with narcolepsy will experience all symptoms.

Common symptoms:

• Abnormal tendency to sleep during the day
• Cataplexy, or momentary paralysis brought on by a sudden emotional reaction such as anger, fear or joy
• Sleep paralysis, or occasional attacks of momentary paralysis when the patient is going to sleep or has just woken up
• Memory loss
• Dream-like hallucinations

There is no cure for narcolepsy. Treatment focuses on alleviating the symptoms so that patients can live normal lives.

Most common treatment techniques:

• Behavior modification, including planned daytime naps
• Prescription stimulants
• Antidepressant medication to suppress cataplexy attacks

Restless legs syndrome

Restless legs syndrome is a sleep disorder in which patients can't help moving their legs, which prevents them from being able to go to sleep. It's more common among middle-aged or older people.

Symptoms:

• Uncomfortable sensations of creeping or crawling deep inside the calves or on the feet, arms or thighs, especially when lying down
• Irresistible impulse to move the legs
• Worsening of symptoms when under stress

Treatment options:

• Muscle relaxation techniques
• Medication, including some forms of tranquilizers

Sleepwalking

Sleepwalking, also called somnambulism, usually occurs during the first third of the night, and the duration of each episode can range from a few minutes to a half-hour. There is some evidence that sleepwalking is genetically linked, occurring most commonly in children aged six to 12. Boys are more likely than girls to sleepwalk. If the sleepwalking begins by age nine, the sleepwalker may continue to sleepwalk as an adult. Other adult sleepwalkers may be experiencing personality conflict or anxiety.

Sleepwalking itself isn't considered medically dangerous, but the sleepwalker may be injured by falling or tripping, going outside the house or even causing a car accident while driving. Experts advise seeking medical help if the sleepwalker is having frequent episodes or is walking outside the house.

Sleepwalking symptoms:

• Walking, sometimes performing other activities such as going to the bathroom, opening closet doors and so on, while asleep
• While sleepwalking, the patient has eyes opened and a dazed facial expression
• Confusion or disorientation when awakened

Treatment options:

• Making the house safe for the sleepwalker, including blocking the top of staircases with a gate and removing objects the sleepwalker might trip over
• Calming bedtime rituals, such as meditation or relaxation exercises
• Avoiding fatigue - being overtired can trigger sleepwalking
• For more severe cases, short-acting tranquilizers may be prescribed

Nightmares and Night Terrors

• Nightmares: Everyone has experienced nightmares, dreams that cause you to wake up frightened and upset. Sometimes they indicate that the sleeper has a psychological disturbance of some kind or is going through a period of extreme anxiety, especially if the sleeper has recurring nightmares with the same or similar themes. However, everyone has nightmares occasionally. There is no specific treatment for nightmares, but psychotherapy may help if they are caused by an underlying psychological disturbance.
• Night terrors: Night terrors are a sleep disorder that's common in childhood, usually occurring between the ages of three and five. The sleeper screams and wakes up terrified, but is unable to explain what happened. The terror may last for 10 or 20 minutes and can be extremely upsetting to the child's parents or caregivers - however, the child usually can't remember the episode in the morning. Children generally outgrow night terrors. The disorder seems to run in families and can occur in adults - often, adult sufferers are experiencing extreme stress or anxiety in their lives.

Insomnia

Everyone has occasionally experienced insomnia, or the inability to fall and stay asleep. For most of us, however, insomnia is temporary.

Some common causes:

• Unusual stress or anxiety
• An environmental change, such as jet lag, a new work schedule or sleeping in an unfamiliar place
• Drinking excessive amounts of caffeinated beverages such as cola, coffee or tea
• Depression
• Endocrine abnormalities, for example hyperthyroidism
• Other sleep disorders, such as restless legs syndrome
• Long-term use of sleeping medications

Sometimes, older people who seek treatment for insomnia are simply experiencing a normal change in sleep patterns - older people tend to fall asleep easily and wake up earlier than they did when they were younger.

Treatment for insomnia depends on the cause.