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Abstract:
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Introduction.
Alpha activity during wakefulness is thought to represent perceptual disengagement and a state of relaxation. Patients with primary insomnia (PIs) have often been observed exhibiting less alpha activity during the transition from wakefulness to sleep. This suggests that such patients are less able to perceptually disengage and/or relax during sleep initiation. Because there are few controlled studies that evaluate peri-sleep onset alpha activity in PIs as compared to good sleeper (GS) subjects, the present study was undertaken to address this issue.
Methods.
Data from 30 PIs and 18 GSs were used for the present analysis. Alpha activity was analyzed in two ways: first, average relative power density for the 15 minutes prior to and following sleep onset was compared for the two groups using 2 T-tests; second, serial T-tests were used to compare the groups for each of the individual time points.
Results.
PIs exhibited significantly less alpha activity for the average 15 minutes prior to sleep onset (17% vs. 25%,p = 0.03).
Following sleep onset the group averages were comparable (8.6% vs. 8.9%, p.=0.76). The serial T-test results suggest that these differences occur most reliably within the 2-5 minutes that precede sleep onset.
Conclusion.
These findings are consistent with the clinical observation that PIs tend to exhibit less alpha activity prior to sleep onset.
What remains to be determined is the manner in which this form of alpha suppression is associated with sleep initiation problems. |
