Study objectives: Determine the relationship of non-rapid eye movement (NREM) electroencephalographic (EEG) spectral measures and the response to cognitive behavioral therapy (CBT) in primary insomnia (PI).
Design: Patients with PI were randomly assigned to CBT or a placebo intervention (PC). Ambulatory polysomnography was performed before and after treatment.
Setting: University medical center sleep laboratory.
Participants: Thirty PI patients with sleep maintenance difficulty evident in subjective sleep measures.
Interventions: CBT and PC.
Results: CBT led to a more rapid decline in EEG delta power over the night, compared with PC. This change was associated with subjective improvement in response to CBT. Furthermore, lower pretreatment peak EEG delta power in the first NREM cycle and a more gradual decline in delta power predicted a better response to CBT. Increased wake time during the day produced by CBT was correlated with an increase in the steepness of the slope of EEG delta power and subjective improvement. Traditional polysomnography measures were associated with the subjective CBT response to a greater degree among patients whose total sleep time estimates better approximated polysomnography-derived total sleep time. In contrast, changes in all-night averaged NREM EEG spectral indices were more strongly related to subjective improvement in individuals who underestimated total sleep time to a greater extent.
Conclusions: CBT led to a more rapid decline in EEG delta power over the night. This change is linked to the therapeutic effect of CBT, which appears to occur in conjunction with an increase in homeostatic sleep drive. Traditional polysomnography indices and all-night averaged NREM EEG measures appear to be related to subjective improvements with CBT in subsets of patients with PI.