“Sleep tight and sweet dreams” used to be the phrase used when bidding a family member good night. Unfortunately, a significant number of individuals have difficulty either falling asleep or staying asleep for the 7 to 8 hours recommended by the National Institutes of Health. (However, this is a general recommendation and varies by both age and the individual. For example, infants need on average about 16 hours of sleep per day, teenagers approximately 9 hours, adults the 7 to 8 recommended hours, with older adults requiring about the same as younger adults or up to 9 hours sleep.) Between 50 million and 70 million individuals are impacted by sleep-related problems. This is a serious issue, as sleep is a neurobiological need. The ultimate result of sustained sleep loss can be death. Not only is a significant percentage of the U.S. population impacted by sleep disorders, sleep has also become a big business; there are over 2,800 U.S.-based sleep centers. Sleep center revenue is expected to climb to $4.4 billion by the year 2011, and this does not account for the estimated $3 billion in revenue to pharmaceutical companies from the 43 million prescriptions written annually for sleep disorders.
The National Institutes of Health has classified over 80 types of sleep disorders. The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM—IV—TR) organizes sleep disorders into four major categories: primary sleep disorders, sleep disorder related to another mental disorder, sleep disorder due to a general medical condition, and substance-induced sleep disorder. Included within these categories causing sleep disturbance are psychiatric illnesses like depression and posttraumatic stress disorder (PTSD); medical or biological contributors like hypertension and coronary artery disease; situational contributors of shift work, poor environ-ment, and jet lag; medicine or drugs, which includes alcohol, stimulants, and narcotics; and numerous others like sleep apnea, genetics, ethnicity, and the aging process. It appears from all the data that the United States is becoming a sleep-deprived nation. The good news is that there is rapidly growing attention to this problem, as more than $110 million has been invested in sleep related research since 1996.
Definition of Sleep Disorder
An all-encompassing definition of a sleep disorder is difficult due to the broad categories and significant number of sleep disorders within each category. However, to establish some frame of reference, following are examples of major sleep disorders as defined by DSM—IV—TR:
Primary insomnia: “Difficulty initiating or maintaining sleep or of a nonrestorative sleep that lasts for at least 1 month (Criterion A) and caused clinically significant distress or impairment in social, occupational, or other important areas of functioning (Criterion B).” This is the most common of the sleep disorders.
Breathing-related sleep disorder: “Sleep disruption, leading to excessive sleepiness or, less commonly, to insomnia, that is judged to be due to abnormalities of ventilation during sleep (e.g., sleep apnea or central alveolar hypoventilation).”
Circadian rhythm sleep disorder: “Persistent or recurrent pattern of sleep disruption that results from altered function of the circadian timing system or from a mismatch between the individual’s endogenous circadian sleep-wake system and exogenous demands regarding the timing and duration of sleep.”
Dyssomnia not otherwise specified includes “complaints of clinically significant insomnia or hypersomnia that are attributable to environmental factors (e.g., noise, light, frequent interruptions); excessive sleepiness that is attributable to ongoing sleep deprivation; ‘Restless legs syndrome’ characterized by a desire to move the legs or arms, associated with uncomfortable sensations typically described as creeping, crawling, tingling, burning, or itching.”
The definitions continue for additional sleep disorders, including nightmare disorder, sleep terror disorder, sleepwalking disorder, sleep disorders related to another mental disorder, sleep disorder due to a general medical condition, and substance-induced sleep disorder.
The Impact of Sleep Disorder
The list of negative impacts from sleep deprivation and disorders is lengthy. The impact can depend upon many factors, including gender; age differences; and situational factors like stress, loss of a loved one, or jet lag. There are the physical consequences like lowered attention and executive functions resulting in loss of productivity at work, and impaired learning and memory. An estimated 56,000 automobile crashes annually are related to driver drowsiness and fatigue. Other impacts are a weakened immune system, a link between brain damage and sleep apnea, the inhibition of aggression and negative consequences to overall mood, emotional impacts such as the correlation between depressive symptoms and prominent fatigue, and an overall impaired quality of life.
Sleep Disorder Treatment: Psychology versus Pharmacology
Focusing on insomnia as the most prevalent of sleep disorders, several treatments are effective, including pharmacology, cognitive-behavioral therapy, stimulus control therapy, biofeedback, and relaxation training. Cognitive-behavioral therapy (CBT) has been shown to be an effective treatment for insomnia. Comparisons between CBT, pharmacological therapy, and the combination of the two on treatment for insomnia suggests that medications and the combination of medication and CBT produced greater short-term effects, but CBT alone appears to have the greatest long-term effect on improving sleep disturbances.
Advancements and Research Results
There is still much to investigate regarding sleep disorders, but much progress has been made. Several clock genes have been discovered that have a significant role in mammalian circadian timing, and newly discovered neurotransmitter systems influence regulation of rapid eye movement (REM). Regarding molecular biological approaches, the hypocretin system has been found to have a role in narcolepsy and behavior control, and cell groups in the hypothalamus and neurochemical phenotypes of neurons are important to REM. Research is also exploring the genetic basis of sleep. Treatment of neurological disorders can cause sleep disorders. Epileptic seizures can place individuals at further risk for sleep disorders. An interesting observation relating to age and gender is that approximately 90% of the individuals impacted by REM behavior disorder (RBD) are male, and most are over 50 years old. Disruption of sleep has also been found with most psychiatric disorders. The same is true for substance abuse.
Conversely, chronic insomnia can put an individual at risk for development of psychiatric disorders. The expression of some genes for synaptic plasticity in children can be impacted by sleep loss. Researchers now better understand sleep and the environment, including the impact of light, temperature, noise, motion (bed partners), location, position, and sleeping surface. Researchers also understand that chronic sleep deprivation can lead to cognitive deficits, weakening of the immune system, weight gain, heart disease, diabetes, and if severe enough even death. From a gender perspective, changes in a woman’s biochemistry, like those associated with pregnancy or menopause, can cause sleep deprivation. Ethnicity is also a factor in sleep disorders. The risk of sleep-disordered breathing (SDB) is approximately twice as great in young African Americans as in Caucasians. Adults that are non-Caucasian are at almost twice the risk of insomnia, which also affects approximately one third of older adults.
Technology has brought new and fresh perspectives to researching sleep disorders over the last 5 years. These include functional neuroimaging technologies like positron emission tomography (PET), functional magnetic resonance imaging (fMRI), single photon emission computed tomography (SPECT), near-infrared optical imaging (NIR), and others that allow researchers to see the brain in new ways. Additionally, electroencephalographs (EEG) brain-mapping studies, combined with electrooculographic (EOG) and submental electromyographic signals (EMG), allow researchers to view the patterns of connectivity between brain regions and how the brain responds while performing specific tasks. They can demonstrate how functionality and cognitive capacity are altered by sleep loss. The combination of pharmacology, technology, and ongoing research into biology, genetics, psychology, and biochemical makeup holds great promise for successful treatment of many of the categorized sleep disorders.
- American Psychiatric Association. (2005). Diagnostic and Statistical Manual of Mental Disorders (4th ed., Text rev.). Washington, DC: Author.
- U.S. Department of Health and Human Services, National Center on Sleep Disorders Research. (2003). 2003 national sleep disorders research plan. NIH publication no. 03-5209. Washington, DC: Author.
- Verbeek, I. H., Konings, G. M., Aldenkamp, A. P., Declerck, A. C., & Klip, E. C. (2006). Cognitive behavioral treatment in clinically referred chronic insomniacs: Group versus individual treatment. Behavioral Sleep Medicine, 4(3), 135-151.
- Wu, R., Bao, J., Zhang, C., Deng, J., & Long, C. (2006). Comparison of sleep condition and sleep-related psychological activity after cognitive-behavior and pharmacological therapy for chronic insomnia. Psychotherapy & Psychosomatics 75, 220-228.