The physiological model is based upon three major findings in people with insomnia; firstly, increased urinary cortisol and catecholamines have been found suggesting increased activity of the HPA axis and arousal; second increased global cerebral glucose utilization during wakefulness and NREM sleep in people with insomnia; and lastly increased full body metabolism and heart rate in those with insomnia. All these findings taken together suggest a dysregulation of the arousal system, cognitive system, and HPA axis all contributing to insomnia.However, it is unknown if the hyperarousal is a result of, or cause of insomnia.
Altered levels of the inhibitory neurotransmitter GABA have been found, but the results have been inconsistent, and the implications of altered levels of such a ubiquitous neurotransmitter are unknown. Studies on whether insomnia is driven by circadian control over sleep or a wake dependent process have shown inconsistent results, but some literature suggests a dysregulation of the circadian rhythm based on core temperature. Increased beta activity and decreased delta wave activity has been observed on electroencephalograms; however, the implication of this is unknown.
A qualified sleep specialist should be consulted for the diagnosis of any sleep disorder so the appropriate measures can be taken. Past medical history and a physical examination need to be done to eliminate other conditions that could be the cause of insomnia. After all other conditions are ruled out a comprehensive sleep history should be taken. The sleep history should include sleep habits, medications (prescription and non-prescription), alcohol consumption, nicotine and caffeine intake, co-morbid illnesses, and sleep environment.
A sleep diary can be used to keep track of the individual’s sleep patterns. The diary should include time to bed, total sleep time, time to sleep onset, number of awakenings, use of medications, time of awakening, and subjective feelings in the morning. The sleep diary can be replaced or validated by the use of out-patient actigraphy for a week or more, using a non-invasive device that measures movement.
