Sleep Homeostasis in Primary Insomnia

Overview

About 10% of the population is believed to suffer from Primary Insomnia. It is also believed that people with chronic insomnia have a sleep system that is essentially out of alignment (we call this "homeostatic dysregulation"). We also know that a certain form of non-medication therapy called cognitive-behavioral therapy is a very effective treatment for insomnia. It is not known, however, whether cognitive-behavioral therapy actually works by bringing the brain's sleep system back into alignment ("sleep homeostasis"). One of the methods used to measure sleep homeostasis is to observe a person's brain waves during sleep and particularly during sleep that follows a period of sleep loss. The purposes of this study are to first learn whether persons with insomnia do have a misaligned sleep system compared to persons who do not have insomnia by assessing the sleep of people before and after a period of extended sleep loss. Second, the study will determine whether cognitive-behavioral therapy can re-regulate the sleep system and its response to sleep loss. Third, the final purpose is to examine whether the immune system of people with insomnia is more altered following sleep loss than in the comparison group and whether cognitive-behavioral therapy can alter immune function.

Despite the magnitude of the problem of Primary Insomnia, and the good efficacy of Cognitive Behavioral Treatment for Insomnia (CBT-I), little is known about the pathophysiology of insomnia or whether treatment alters the factors that are thought to maintain chronic insomnia. Three main factors have been explored as contributing to chronic insomnia: hyperarousal, circadian dysrhythmia, and homeostatic dysregulation. Most of the empirical work has been related to the role of hyperarousal along three dimensions: somatic, cognitive, and cortical. The present study is focused on homeostatic abnormalities and secondarily on hyperarousal as exhibited in subjects with Primary Insomnia (PIs) compared to Good Sleeper controls (GSs). Homeostatic abnormalities will be assessed by evaluating how patients with insomnia respond to sleep deprivation. This study will use a Modified Sleep Deprivation and Multiple Sleep Latency Test (MSD/MSLT) procedure. Response to the procedure will be assessed in terms of sleep continuity, sleep architecture and electroencephalographic (EEG) power spectral changes during recovery sleep. Hyperarousal will be evaluated using serial measures of somatic (cortisol) and cortical (EEG Beta/Gamma activity) arousal across the sleep deprivation protocol. These parameters will be evaluated both prior to and following CBT-I in PIs and following an equivalent time interval in GSs.