A High Density EEG Comparison of Sleep Patterns in Insomnia

Insomnia, defined as a subjective report of difficulty initiating sleep, maintaining sleep, and/or non-restorative sleep, leads to significant daytime dysfunction and increased health risks. A commonly held hypothesis is that insomnia is caused by a state of hyperarousal, but the neurobiological mechanisms of hyperarousal in insomnia are poorly understood, in part because of limitations in our ability to image the brain during normal human sleep with sufficient temporal resolution. Furthermore, the efficacy of insomnia treatment is judged by subjective report of the patient and demonstration of changes in sleep latency and/or sleep amount which are generally small in magnitude; there are currently no data to demonstrate that insomnia treatments correct any functional abnormalities in the sleep process that likely contribute to neurobehavioral abnormalities and health risks. The goals of the proposed study are to use high density EEG to define abnormalities in specific aspects of sleep in insomnia patients compared to healthy sleeping control subjects to define biomarkers that will both increase our understanding of the pathophysiology of insomnia as well as provide targets to assess treatments for insomnia.

Recent advances in electroencephalographic recording techniques have produced new ways to probe the process and function of sleep. Through the use of high-density EEG (hdEEG, up to 256 channels), it is possible to approach the spatial resolution of other brain imaging modalities while affording the millisecond temporal resolution of EEG and providing a direct measure of the underlying brain activity, unlike the indirect and/or secondary biophysical signals of brain hemodynamics/metabolism obtained with PET or SPECT that are suboptimal for exploring the short-lived spatio-temporal dynamics of many brain processes.

Here we used hdEEG to try to characterize topographic changes in sleep EEG expression in individuals with insomnia compared to normal controls. We further used serial awakenings to determine if individuals with insomnia were more likely to subjectively report being awake when they were sleeping, and study instances where a direct confirmation of sleep was followed by a subjective report of wakefulness to see if they are characterized by changes in EEG oscillations.

Eligibility Criteria:
Inclusion Criteria:

* 18-45 years old
* English speaking, reading, and writing
* For control subjects: Insomnia Severity Index (ISI) less than or equal to 6 and does not meet criteria for insomnia
* For insomnia subjects: ISI greater than or equal to 7, meets criteria for insomnia, and reports insomnia symptoms for at least 6 months

Exclusion Criteria:

* Imminent danger to self or others
* Clinical diagnosis of dementia
* Active Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV Axis I disorder or alcohol or drug dependence or abuse
* Other sleep disorders aside from insomnia
* History of significant head trauma or loss of consciousness over 30 minutes
* Regular use of psychotropic medications in past 4 weeks
* Regular tobacco use
* Drinking more than 3 caffeinated beverages per day
* Significant neurological or medical illness
* Pregnant, less than 6 months post-partum, or planning to become pregnant during the study
* Left-handedness
* Body Mass Index (BMI) greater than 40
* Apnea Hypopnea Index (AHI) greater than 10 on Apnea Link
* Mini mental status exam score less than 27