NATURAL LIGHT EXPOSURE, HEALTHY ELDERLY PEOPLE AND SLEEP A FIELD STUDY

摘要

Among 14 independently living, mobile andhealthy elderly people in The Netherlands was conducted to see whether exposure duration of high intensity, natural, light is related to sleep quality, and more general the amplitude of the sleep-wake cycle. The elderly wore for 5 consecutive days in summer and 5 days in winter, an actiwatch, an apparatus measuring their activity and their exposure to light over time, continuing their normal living situation. Derived from the activity data, data about sleep efficiency and sleep latency could be obtained. The subjects also filled out the PSQI questionnaire, rating whether they are good or bad sleepers. Due to the Dutch climate, it was expected that exposure to daylight would be lower in winter than in summer. Consequently, it was expected that sleep quality would be worse in winter. However, the sleep quality measures did not differ significantly between summer and winter. The results did show a positive correlation between sleep efficiency and exposure duration to high intensity light, meaning that more light is related to efficient sleep. There was a tendency of less frequent napping for longer exposure duration. As expected, exposure duration to light above 1000 lux was shorter in winter than in summer.