Abstract
We aimed to assess which quantitative EEG changes during daytime testing in patients with sleep disorder (primary insomnia and excessive daytime sleepiness groups). All experimental study participants were subjected to a long-term test for maintaining attention to sound stimuli, and their EEGs were recorded and then processed, using wavelet analysis, in order to estimate the power and frequency structure of alpha activity. In healthy subjects, the maximum increase in the alpha rhythm occurred near 9 Hz. Patients with primary insomnia were characterized by an increase in the amplitude of the alpha rhythm near 11 Hz. For subjects with sleep disorders, an increase in the amplitude of the alpha rhythm was observed in the entire frequency range (7.5–12.5 Hz), with a maximum increase at 9–10 Hz. Significant differences () for changes in the alpha rhythm dynamics in the course of performing the attention test were observed in the frequency range of 7.5–10.5 Hz between the control group and patients with sleep disorders. The ratios of the alpha rhythm power values for passive stages with closed eyes before and after active stage were significantly different among the groups of healthy sleep volunteers, patients with primary insomnia, and patients with impaired sleep hygiene within the range of 9.5 to 12.5 Hz. The results of the current study supported the notion of a 24-h hyperarousal in primary insomnia.
Highlights
The prevalence of chronic primary insomnia in the general population is approximately 10%, transient symptoms of sleep disorders are detected much more often—in30–35% of people [1,2]
A better understanding of the primary insomnia pathophysiology appears useful in assessing the potential of various treatment techniques, and in developing novel approaches that target neurophysiological characteristics correlating with primary insomnia symptoms
We present a quantitative description of the change in the alpha rhythm during the daytime in patients with primary insomnia
Summary
The prevalence of chronic primary insomnia in the general population is approximately 10%, transient symptoms of sleep disorders are detected much more often—in30–35% of people [1,2]. The change in neurophysiological characteristics of patients with insomnia in the presleep period and during their sleep has been sufficiently studied [9,10,11,12,13]. It has been shown that patients with insomnia, in spite of their subjective complaints for daytime somnolence, as well as their significantly shorter nocturnal sleep, do not exhibit augmented somnolence, as compared with normal sleepers [19,20,21]. Recent evidence suggests that patients with primary insomnia show changes in neurophysiological activity during normal daytime wakefulness compared to those with normal sleep [22,23,24]. The presented characteristics of EEG activity are weakly specific, since they can be observed in normal sleepers as well, for example, in conditions of visual fatigue accumulation [26,27]
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