| Summary: | 博士 === 國立政治大學 === 心理學系 === 104 === Introduction
Hyperarousal has been recognized to be a major etiological factor of chronic insomnia. Cumulated research evidences have demonstrated that chronic insomnia patients are
hyperaroused in somatic, cognitive, and behavioral aspects. According to Spielman’s 3P Model of Insomnia, there were different factors are involved at different points during the course of insomnia. However, there are seldom study to investigate the difference mechanism of hyperarousal in the course of the development of insomnia.
The present study used cross-sectional design to compare the difference of good sleeper (low sleep vulnerability, LV), acute insomnia (high sleep vulnerability, HV),
and chronic insomnia (CI) in stress reaction (eg. reactivity and recovery), attentional bias (eg. vigilance and disengagement), and sleep associated monitoring behaviors to investigate the underlying mechanism of hyperarousal. Furthermore, the study examined the correlation between attentional bias indices and subsequent pre-sleep arousal to investigate the impact of attentional bias on sleep in different groups.
Method
The present study recruited fifty-eight subjects, aged between 24-48. They included eighteen chronic insomniacs (CI) diagnosed ICSD-3, nineteen healthy individuals
scoring high (HV) and twenty-one healthy individuals scoring low (LV) on the Ford Insomnia Response to Stress Test (FIRST). All subjects visited sleep lab twice. During the first visit, the subjects filled in a package of questionnaires, and went through psychophysiological recording (including) of stress reaction, and a visual dot-probe task. They then were required to keep a sleep log and wear actigraphy at home for one-week to make sure they followed a regular sleep schedule. During the second visit, subjects went through a pre-sleep physiological recording (including peripheral temperature, skin conductance, and EEG) and filled in two questionnaires (Pre Sleep Arousal Scale [PSAS] and Sleep Associated Monitoring Index[SAMI]) at three time points and had a PSG recording to screen for sleep disorders.
Result
One-way ANOVAs were conducted to compare the differences of stress reaction/recovery among three groups. Two-way ANOVAs were used to compare the differences in attentional bias (vigilance/ disengagement) of threatening and sleep-related stimulus among three groups. In stress related physiological activity, CI and HV showed slower recovery rate than LV. Considering attentional bias, HV had
significant vigilance and disengagement bias to threatening pictures, and CI had significant disengagement bias to sleep-related pictures. CI and HV also showed more prevalent sleep-associated monitoring behaviors than LV. Furthermore, Spearman’s correlation was used to examine the association between attentional bias and pre-sleep arousal. The result shows the attentional bias of HV had negative correlation with reduction of high frequency EEG and somatic sub-score on the PSAS. In contrast to our prediction, CI showed positive correlation between decrease of skin conductance
and the cognitive sub-score on the PSAS.
Conclusion
The study showed that stress recovery ability and stress-related attentional bias were the major differences between individuals with low and high sleep vulnerability,
indicating that increased information processing to threats and stress-related stimulus as well as decreased recovery ability of autonomic arousal in reacting to stress may
predisposed an individual to stress-related sleep disturbances. On the other hand, the
attention shift from threat toward sleep can differentiate chronic insomnia from those individual with frequent acute insomnia. Moreover, the difficulty in disengagement
from sleep-related stimulus, rather the vigilance, might explain the cause of hyperarousal that perpetuate insomnia. The results support the transition of arousal from general treat to sleep-related stimulus in the development of chronic insomnia. The study not only further the understanding of the etiological mechanism of insomnia, but also imply that different strategies should be applied in the treatment of
acute and chronic insomnia. It also highlights the importance of preventive intervention for individuals with high sleep vulnerability
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