The hyperarousal model of insomnia: A review of the concept and its evidence

There is growing interest in insomnia both from the perspective of recent advances in clinical management as well as research aimed at elucidating its pathophysiology. This theoretical overview of insomnia describes the negative impact, etiological considerations, and pharmacological and behavioral treatments for the disorder, with an emphasis on areas receiving increased research attention. Insomnia, the most prevalent sleep disorder, affects 10-15% of the general population. In population-based studies severe insomnia has been shown to last for a median of 4 years. In addition, insomnia has a significant negative impact on an individual's work, physical, and social performance as well as overall quality of life. Furthermore, the economic cost of insomnia related to lost productivity, work-related accidents, absenteeism, and health-care costs are enormous. There is increasing evidence linking the precipitation of insomnia to stress, and converging evidence from cognitive, endocrine, neurological, and behavioral domains provide clear evidence for hyper-arousal in insomnia. However, there remains no consensus regarding the specific etiological mechanisms of this disorder. Although the pathophysiology of primary insomnia remains an enigma, numerous treatments both pharmacological and behavioral have been developed and found to be efficacious in controlled studies. Despite the wide availability of pharmacological treatments and increased knowledge of behavioral interventions, the vast majority of individuals with insomnia do not appear to be receiving adequate treatment. The inadequate treatment of insomnia leads to several important and under-recognized consequences including subsequent development of psychiatric disease and increased substance use.

Insomnia causes, consequences, and therapeutics: an overview.

Problems with sleep are one of the commonest reasons for seeking medical attention. Knowledge gained from basic research into sleep in animals has led to marked advances in the understanding of human sleep, with important diagnostic and therapeutic implications. At the same time, research guided by human sleep disorders is leading to important basic sleep concepts. For example, sleep may not be a global, but rather a local, brain phenomenon. Furthermore, contrary to common assumptions, wakefulness, rapid eye movement (REM) and non-REM sleep are not mutually exclusive states. This striking realization explains a fascinating range of clinical phenomena.

Insights from studying human sleep disorders

The comorbidity of insomnia, chronic pain, and depression: dopamine as a putative mechanism.

There is a stark contrast between our attitudes to sleep and those of the pre-industrial age In Shakespeare's Julius Caesar we are told to "Enjoy the honey-heavy dew of slumber" There seems little chance of this today, as we crave more, work more and expect more, and, in the process, abandon sleep Our occupation of the night is having unanticipated costs for both our physical and mental health, which, if continued, might condemn whole sectors of our society to a dismal future

The rhythm of rest and excess

Study Objectives: The objectives of this study were to: 1) demonstrate the feasibility of combining polysomnography and SPECT neuroimaging to study NREM sleep in primary insomnia and 2) evaluate possible functional CNS abnormalities associated with insomnia. Design: Patients with insomnia and good sleeper controls were studied polysomnographically for three nights with a whole brain SPECT Scan of NREM sleep on Night 3. Groups were screened for medical/psychiatric history, substance use, and matched on age, body mass index, and education. Setting: Sleep Research Laboratory and Nuclear Medicine Center Participants: Nine females, 5 patients with chronic psychophysiologic insomnia and 4 healthy good sleepers (mean age 36 years, SD 12, range 27-55). Interventions: N/A Measurements and Results: Tomographs of regional cerebral blood flow during the 1st NREM sleep cycle were successfully obtained. Contrary to our expectations, patients with insomnia showed a consistent pattern of hypoperfusion across all 8 pre-selected regions of interest, with particular deactivation in the basal ganglia (p=.006). The frontal medial, occipital, and parietal cortices also showed significant decreases in blood flow compared to good sleepers (p<.05). Subjects with insomnia had decreased activity in the basal ganglia relative to the frontal lateral cortex, frontal medial cortex, thalamus, occipital and parietal cortices (p<.05). Conclusions: This study demonstrated the feasibility of combining neuroimaging and polysomnography to study cerebral activity in chronic insomnia. These preliminary results suggest that primary insomnia may be associated with abnormal central nervous system activity during NREM sleep that is particularly linked to basal ganglia dysfunction.

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Jean M. Ryan

Papers

Neuroimaging of NREM sleep in primary insomnia: a Tc-99-HMPAO single photon emission computed tomography study.