Electronic media are widespread and research has revealed connections between media use and sleep loss. In this study we aimed to elucidate how many media users get insufficient sleep and whether lengthy media use before sleep curtails sleep. Registered monitor members were surveyed twice on the Internet. The prevalence of self-perceived insufficient sleep ascribed by respondents to using electronic media before sleep was 48.0% (first survey) and 45.0% (second survey). Younger respondents more frequently ascribed using media before sleep as a factor in their perceived insufficient sleep than older respondents. After excluding respondents who ascribed their perceived insufficient sleep to factors other than the electronic media, the sleep duration before a workday was 6.38 Ϯ 1.04 h for light media users (<2.5 h) before sleep, 6.20 Ϯ 1.10 h for intermediate users (Ն2.5 and <3.5 h) and 6.22 Ϯ 1.09 h for heavy users (Ն3.5 h). A Scheffe analysis revealed a significant difference between the light users and medium users (P = 0.02), and between light users and heavy users (P = 0.03). Only 29.0% of light users perceived they had insufficient sleep compared to 53.5% of heavy users. Users who perceived they had insufficient sleep reported a greater disparity in their sleep duration before workdays compared with that before non-workdays (P < 0.001) and a greater disparity between their perceived sufficient sleep hours and their actual sleep time before workdays (P < 0.001). There was a significant difference in disparity between perceived sufficient sleep and actual sleep time before workdays among media use groups (P = 0.002). Because half the respondents ascribed insufficient sleep to using electronic media, attention should be given to media use before sleep as a cause of perceived insufficient sleep. Figure 1 The flow diagram of the progress throughout this study. Media use and sleep complaints 205

We investigated changes in the activity of the autonomic nervous system (ANS) in the relaxed condition in subjects who felt sleepy, but were unable to sleep. A total of 1021 subjects underwent daytime polysomnography. The sleep latency (SL) and the visual analog scale (VAS) were used to assess "immediate" objective and subjective sleepiness, respectively. The subjects were assigned to an "Alert-Alert" group (VAS Յ 25 mm, SL Ն 8 min), a "Sleepy-Alert" group (VAS Ն 75 mm, SL Ն 8 min), or a "Sleepy-Sleepy" group (VAS Ն 75 mm, SL Յ 4 min). In order to assess the ANS, the spectral analysis and the geometric method were used. The ANS data collected during the relaxed condition (after lights off, post-LO) was compared to that obtained during the control condition (before lights off, pre-LO). From the spectral analysis, a significant decrease of sympathetic function and an increase of parasympathetic function at post-LO in the Sleepy-Sleepy group, a tendency for sympathetic function decrease at post-LO in the Alert-Alert group, and no significant changes to sympathetic and parasympathetic function in the Sleepy-Alert group were observed. The results from the geometric method supported the results of the spectral analysis in the Alert-Alert group and the Sleepy-Sleepy group. The results of this study suggest that the ANS plays a role in individuals who are unable to sleep even though they feel sleepy and are given the opportunity to sleep.