Institute for Continuing Education

Correlates of Sleep Complaints in Adults

Course Objectives

Upon successful completion of this module, you will be able to:

• Identify and discuss the relationships among clinical correlates of insomnia and quantitative EEG measures in patients with insomnia.
• Describe the relationship of stress and coping skills, and the potential mediating role of pre-sleep arousal, to sleep patterns in good sleepers and insomnia sufferers.
• Describe the results of the evaluation of the clinical correlates of the electroencephalographic spectral profile in patients with insomnia.
• Explain the role of insomnia as a correlate of sleep complaint.

Course Information

Quantitative EEG studies have consistently reported alterations in EEG power among patients with insomnia in comparison with age-matched, healthy control subjects. Heightened beta activity and attenuated delta power during the sleep onset period are the most reliable alterations, although increases in alpha power have been noted as well (1–3). Merica et al. (4) recently reported that alterations in EEG spectral power among patients with insomnia are not restricted to the sleep onset period; instead, these differences are seen throughout the night, during both non-REM and REM sleep. The EEG spectral profile of patients with insomnia is consistent with hyperarousal and has generated a lot of interest because it supports the hypothesis that heightened CNS activity, including cortical arousal, plays a role in insomnia (5).

Although it has been suggested that the EEG spectral profile of patients with insomnia is related to clinical correlates of the disorder, previous studies have not investigated these relationships. In the preliminary study reported here, we evaluated symptoms of stress and depression in conjunction with laboratory sleep studies in a sample of adults with chronic primary insomnia. We hypothesized that symptoms of stress and depression were likely correlates of EEG spectral power because each has been independently associated with hyperarousal during sleep and waking(6, 7) and because each is commonly associated with insomnia. Specifically, we hypothesized that the tendency to experience stressrelated intrusive thoughts, subjective stress burden, and symptoms of depression would be positively correlated with indices of hyperarousal during sleep, indicated by attenuation of delta power and heightened alpha and beta power. Because subjective sleep complaints are also thought to reflect hyperarousal during sleep (4, 8), we also hypothesized that heightened symptoms of stress and depression would be associated with subjective sleep complaints. Symptoms of stress were operationally defined as the tendency to experience stress-related intrusive thoughts and subjective stress burden. Each of these is more strongly related to sleep than are checklist measures of stressful life events (9, 10).