| Summary: | 碩士 === 國立政治大學 === 心理學研究所 === 98 === Objective：Previous studies confirmed that light exposure before sleep has negative impacts on sleep, including increased sleep onset latency and decreased deep sleep in the first sleep cycle. However experimental manipulations in those studies, such as exposure to bright light or to monochromatic light of specific wavelength and participants keeping a constant posture or light exposure for more than 6 hours are very different from daily life situation. It was not clear that whether those results could be generalized to everyday life. In our study, experiment condition was designed to approximate everyday life in order to examine the effect of presleep light exposure on daily life situations.
Methods：The present study adopted within-subjects design. We used fluorescent light of color temperature of 5000K or 3000K in the experiment and the results were compared with dim light. Nine normal subjects participated in the study. They kept a regular sleep schedule during week before experiment. They came to sleep lab on three experiment nights and exposed to different light for three hours before sleep. During light exposure, EEG power, heart rate and subjective sleepiness were assessed every 30 minutes. For the sleep after light exposure, we analysed sleep onset latency, slow-wave sleep (SWS) duration and delta power after light exposure.
Results： Subjective sleepiness decreased, sleep onset latency increased and SWS significantly decreased under color temperature of 5000K compared with color temperature of 3000K and dim light. Theta/low-frequence alpha (5-9Hz) power was lower under the color temperature of 5000K than dim light, but there were no effects of light on other EEG power. Effects of light exposure on heart rate and delta power were not evident. When 3000K compared with dim light, there were no significant differences on all the variables.
Conclusion： Compared with previous experiments, our study showed similar results when experiment condition was close to everyday life. Exposure to light of high color temperature decreases participants，sleepiness and influences their sleep by increasing sleep onset latency and decreasing SWS duration. When compared with dim light, exposure to light of low color temperature does not influence sleep. These findings implies that light of low color temperature should be used before sleep in order to avoid the detrimental effects of light on sleep.
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