Does television viewing cause delayed and/or irregular sleep-wake patterns?

Previous studies have suggested that the longer duration of television (TV) viewing is related to delayed sleep-wake patterns. However, since these studies were based on a questionnaire survey method, a causal relationship between TV viewing and sleep-wake patterns could not be clearly determined. Therefore, to clarify the causal relation between TV viewing and sleep-wake patterns, the present study employed an intervention method. Eight university students and eight elderly people participated in this study for 2 weeks, excluding weekends. They were asked to follow their regular routine during the study; however, their TV viewing was limited to 30 min per day in the second week. The results indicate that the effects of the restriction on TV viewing differed between the two age groups. This restriction affected the sleep-wake pattern and motor activity of university students. When TV viewing was limited, they went to bed earlier and slept for a longer time. Therefore, this suggests that TV viewing could be one of the causal factors of delayed bedtime among university students. At the same time, when their TV viewing time was restricted, their motor activity decreased at around 7-8 AM and 3 PM, and their total sleep time during the daytime increased. This suggests that TV viewing may also have positive effects on students' daytime activities, such as maintaining regularity of their sleep-wake patterns. On the other hand, the sleep-related variables and daily motor activities of the elderly people were hardly affected by the restriction on their TV viewing time.