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MEDICAL BIOLOGY: ON CHRONIC INSOMNIA

The following points are made by Michael H. Silber (New Engl. J. Med. 2005 353:803):

1) Insomnia is defined as difficulty with the initiation, maintenance, duration, or quality of sleep that results in the impairment of daytime functioning, despite adequate opportunity and circumstances for sleep.[1,2] (Difficulty with sleep maintenance implies waking after sleep has been initiated but before a desired wake time.) Most research studies adopt an arbitrary definition of a delay of more than 30 minutes in sleep onset or a sleep efficiency (the ratio of time asleep to time in bed) of less than 85 percent.[1] However, in clinical practice, a patient's subjective judgment of sleep quality and quantity is a more important factor. Transient insomnia lasts less than one week, and short-term insomnia one to four weeks.

2) Chronic insomnia -- insomnia lasting more than one month[3] --has a prevalence of 10 to 15 percent[2,4] and occurs more frequently in women, older adults, and patients with chronic medical and psychiatric disorders.[1] It may follow episodes of acute insomnia in patients who are predisposed to having the condition and may be perpetuated by behavioral and cognitive factors, such as worrying in bed and holding unreasonable expectations of sleep duration.[5] Consequences include fatigue, mood disturbances, problems with interpersonal relationships, occupational difficulties, and a reduced quality of life.

3) Insomnia can be classified as primary or secondary.[3] The pathogenesis of primary insomnia is unknown, but available evidence suggests a state of hyperarousal. As compared with controls, patients with insomnia show increased global cerebral glucose metabolism on positron-emission tomography when awake and asleep, increased beta activity and decreased theta and delta activity on electroencephalography during sleep, an increased 24-hour metabolic rate, and higher levels of secretion of adrenocorticotropic hormone and cortisol.

4) Cognitive behavioral therapies comprise a group of techniques that address the factors that help perpetuate chronic insomnia, regardless of the cause. Stimulus-control therapy assumes that insomnia is a maladaptive response to factors such as bedtime and the bedroom environment (for example, regularly reading or watching television in bed rather than sleeping) and requires a learning process to reassociate the bed with sleep. Sleep-restriction therapy is based on the premise that people with insomnia can learn to increase their sleep time by inducing temporary sleep deprivation through voluntarily reducing their time in bed. Relaxation therapies are predicated on the hypothesis that insomnia is associated with hyperarousal.[1] The cognitive component of such therapies involves the education of the patient about sleep needs, the correction of unrealistic expectations, and a discussion of anxiety and catastrophic thinking, such as exaggerating to oneself the consequences of poor sleep. Sleep-hygiene education addresses extrinsic factors that can perpetuate insomnia, such as noise in the bedroom and the use of caffeine.

References (abridged):

1. Morin CM, Hauri PJ, Espie CA, Spielman AJ, Buysse DJ, Bootzin RR. Nonpharmacologic treatment of chronic insomnia: an American Academy of Sleep Medicine review. Sleep 1999;22:1134-1156

2. Costa e Silva JA, Chase M, Sartorius M, Roth T. Special report from a symposium held by the World Health Organization and the World Federation of Sleep Research Societies: an overview of insomnias and related disorders -- recognition, epidemiology, and rational management. Sleep 1996;19:412-416

3. The international classification of sleep disorders, revised: diagnostic and coding manual. Rochester, Minn.: American Sleep Disorders Association, 1997

4. Morin CM, Culbert JP, Schwartz SM. Nonpharmacological interventions for insomnia: a meta-analysis of treatment efficacy. Am J Psychiatry 1994;151:1172-1180

5. Spielman AJ, Caruso LS, Glovinsky PB. A behavioral perspective on insomnia treatment. Psychiatr Clin North Am 1987;10:541-553

New Engl. J. Med. http://www.nejm.org

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