A number of sleep disorders can disrupt your sleep quality and leave you with excessive daytime sleepiness, even if enough time was spent in bed to be well rested. (See “Common Signs of a Sleep Disorder”.) More than 70 sleep disorders affect at least 40 million Americans and account for an estimated $16 billion in medical costs each year, not counting costs due to lost work time and other factors. The four most common sleep disorders are insomnia, obstructive sleep apnea (sleep-disordered breathing), restless legs syndrome (RLS), and narcolepsy. Additional sleep problems include sleep walking, sleep paralysis, night terrors, and other “parasomnias” that cause abnormal arousals.

Insomnia
Insomnia is defined as having trouble falling asleep or staying asleep, or as having unrefreshing sleep despite having ample opportunity to sleep. Life is filled with events that occasionally cause insomnia for a short time. Such temporary insomnia is common and is often brought on by stressful situations such as work, family pressures, or a traumatic event. A National Sleep Foundation poll of adults in the United States found that close to half of the respondents reported temporary insomnia in the nights immediately after the terrorist attacks on September 11, 2001.

Chronic insomnia is defined as having symptoms at least 3 nights per week for more than 1 month. Most cases of chronic insomnia are secondary, which means they are due to another disorder or medications. Primary chronic insomnia is a distinct sleep disorder; its cause is not yet well understood.

About 30 - 40 percent of adults say they have some symptoms of insomnia within any given year, and about 10 - 15 percent of adults say they have chronic insomnia. Chronic insomnia becomes more prevalent with age, and women are more likely than men to report having insomnia.

Insomnia often causes problems during the day, such as excessive sleepiness, fatigue, a lack of energy, difficulty concentrating, depressed mood, and irritability. Due to all of these potential consequences, untreated insomnia can impair quality of life as much as, or more than, other chronic medical problems.