Limitations

4.5.1 Time of Day and Bedroom Presence of Media

This study on sleep and electronic media use specifically examined the amount of time spent per day with different types of media, but the time of day use in relation to bedtime or the presence of electronic media in the bedroom was not subject to investigation. Many children and adolescents use electronic media in their bedrooms before bedtime or even in bed as a pre-sleep activity or sleep aid (Eggermont and Van den Bulck 2006). Therefore, the methods used in this study to investigate media use and adolescent sleep do not allow for conclusions about whether or not evening or nighttime media use show stronger relationships to IC than

media use throughout the course of a day. Past studies suggest that media use before bedtime can cause sleep disruption. Also, hypotheses for mechanisms by which sleep is disrupted by media use propose proximity to bedtime as a factor causing displacement of sleep (displacement hypothesis), arousal (cognitive, physiological and/or emotional in nature) or shift circadian rhythm through exposure to bright light (Cain and Gradisar 2010). Yet, this study was able to show that increased amounts of time spent per day with certain types of media also showed relationships to IC. This may reflect the fact that adolescents with increased use of media usually spend part of this time using media in the evenings or before bedtime, which has been shown in past studies (Calamaro et al. 2009). Therefore, pre-sleep media use is likely to be accountable for the positive association between media use and IC presented in this study.

4.6.2 Changes in Media Use Patterns Since 2006

The KiGGS was conducted from 2003 to 2006 and since then media use and access to electronic media has been shown to be increasing in Western countries. In particular, the introduction of the smart phone has made a significant impact on the modern day media landscape. A large study conducted by the Henry J. Kaiser Family Foundation in the United States titled “Generation M - Media in the Lives of 8- to 18-Year Olds” published in 2010 states that “The transformation of the cell phone into a media content delivery platform, and the widespread adoption of the iPod and other MP3 devices, have facilitated an explosion in media consumption among American youth … The development of mobile media has allowed – indeed, encouraged – young people to find even more opportunities throughout the day for using media, actually expanding the number of hours when they can consume media, often while on the go” (Rideout et al. 2010, p. 3). A considerable increase in media exposure by 2

¼ hours compared to similar data collected in 2004 is depicted in this study. American youths were exposed to an average amount of 7.38 hours of media content per day, yet, factoring in the multitasking proportion of 29% the average amount of exposure per day in fact constituted a total of 10.45 hours. Furthermore, bedroom presence of cable television, DVD players, computers and access to the internet was also shown to be increasing. In Germany, one of the largest studies on media use in adolescence over the time course from 1998 to present has been the JIM study (“Jugend, Information und (Multi-) Media”) (Feierabend et al. 2013). This study has been conducted every year on a large representative sample and data on media use in adolescents aged 12 to 19 years is obtained in order to investigate changes in media use patterns over time. Results of this study show, for example, that the average time spent per

day using the internet in 2013 was 179 minutes, which was an increase of 48 minutes in only one year when compared to results from 2012. 72% of adolescents in 2013 owned a smart phone with a touch screen and internet access, which represents a device that was not subject to investigation in KiGGS as smart phones were not yet widely available during the time of data collection in 2003 to 2006.

With respect to these changes in the media landscape over the past years it becomes clear that electronic media use patterns today incidentally differ from patterns recorded by the KiGGS from 2003 to 2006. Concerning sleep research, Zimmermann notes in a research brief from 2008 on children’s media use and sleep problems for the Henry J. Kaiser Family Foundation that young people’s media environments have changed significantly and much evidence on this topic collected in the past needs up-to-date supporting evidence. Newer studies should take the different and evolving media types, contents and times of day of media use into consideration. Yet, this study and other studies from the past provide an important basis for substantiation of associations between electronic media use and sleep disturbance in adolescence. This study was able to demonstrate that different media types showed different associations to IC and that a gender difference was seen in these associations. Increase in media use and changes in media use patterns make further studies in this field of sleep research necessary and, particularly this increase in use in past years, should emphasize the relevance of research in this field. Further studies can use knowledge from this study and past studies in order to further investigate known associations and follow changes over time. For example, the investigation of different media types will become increasingly inappropriate, as various different media contents can now easily be accessed through fewer or even just one media device. Further studies should therefore emphasize media content rather than the media type and, in particular, take multitasking with different types and contents of media into account.

4.6.3 Cross-Sectional and Questionnaire-Based Design

Lastly, the cross-sectional and questionnaire based study design of the KiGGS does not allow for implications about a causality between electronic media use and IC in adolescents. This study shows mere associations between these investigated subjective variables at a certain point in time. Causality between independent and dependent variables could be investigated in an experimental study with a longitudinal design, in which media use, arousal and sleep measures, such as vital signs and electroencephalographic measures during media use and sleep, are investigated over a longer period of time.