This study examined the data from the existing Eurobarometer reports in order to analyse how the SB prevalence in European adolescents has changed over 15 years (2002-2017) and if differences between girls and boys existed. The main findings were that (a) although EU adolescents show high levels of SB, the prevalence of SB between 2005 and 2017 remains similar (74.2% to 76.8%; p > 0.05) with no significant differences over time for girls or boys; (b) girls and boys show similar prevalence of SB in all studied years.
Previous research has assessed the prevalence of adult SB across European populations based on 2002, 2005, 2013 and 2017 Eurobarometer data [31, 32, 36] but, to the best of our knowledge, this is the first study focused on adolescents. The Global Matrix project can be used to identify the percentage of European adolescents exceeding the 2-h of recreational screen time per day [26]. However, the total daily SB performed by European adolescents was still missing, and this research provides an initial approach to mend this gap. A high proportion of European adolescents, 76.8% in 2017, reported sitting times in excess of 4h30min, which is the threshold for SB. These rates of SB are higher than what has been reported for adults from the Eurobarometer data sets [31]. Unlike adults, however, this study did not reveal significant differences by gender in the prevalence of SB [31].
Although compulsory school usually ends at the age of 16 in European countries, school attendance may still account for the high percentage of SB in adolescents, as many still attend high-school or other educational centres through the age of 18., Thus, although some exceptions might exist (physical education classes, laboratory work, fieldwork, some technology or art classes, etc.), adolescents at school tend to accumulate more than 5 h of SB just during a typical school day [37]. This may also at least partly explain the lack of differences across the years, the lack of difference between genders, and the higher prevalence of SB of adolescents compared to adults. After-school activities may also play a significant role in the total sitting time accrued, as adolescents spend an average of 59% of their after-school time in sedentary activities (from 27.7% to 88.9%) and screen-related activities usually represent the main sedentary activity [38]). Thus, in order to develop and analyse the impact of future policies and interventions addressing SB in adolescents, it is not only important to monitor daily sitting time, but to also consider the environment (i.e. educative centre or out the educative centre) and the activity itself (e.g. screen-related activity; educational-related; social-related activity; etc.).
Regarding gender differences, most existing studies with adolescents suggest that girls accrue higher average sitting time than boys [37, 39-41]. The findings from our study are not in line with this, as no gender differences were seen in any of the study years. The lack of differences may be due to SB being self-reported, as opposed to more objective data such as from an accelerometer [32, 36]. Another possible explanation of the lack of gender differences might be the low sample size in the Special Eurobarometers as previous studies reported that girls and boys engage differently in sedentary activities, with boys reporting more TV or computer games, and girls reporting more time in communication or social media activities [17, 18]. Thus, further studies are needed to verify or reject the findings reported in our study.
To the best of the authors’ knowledge, only seven of the 28 EU countries (Austria, Belgium, Finland, France, Germany, Spain and The UK) included some kind of reference for sedentariness for children and youth in their national guidelines before publication of the latest Eurobarometer report (2017) [22-24, 42-46]. This is in contrast to the EU Working Group “Sport and Health” recommendations in 2008 to reduce SB in school-age children [21]. Moreover, the existing reports about PA from the EU countries show a high percentage of adolescents exceeding 2-hours of screen-based entertainment per day [26], but do not monitor the daily sitting time of this same population. Since 2017, more European countries have developed or updated national guidelines related to SB in adolescents (Greece, Dutch, Latvia or the UK [47-50]). Nonetheless, other than recommendations like exist in France (“children between 6-17 years old should not accumulate sitting bouts for > 2-h long”) [43], most other existing guidelines only mention SB under a qualitative perspective [42, 44-48], with quantitative recommendations mainly focused on screen-related activities.
Limitation and strengths
This study has some limitations to be acknowledged: (a) Less than 600 adolescents were reported in three of the four Eurobarometer reports, so findings should be analysed carefully; in this regard, existing Special Eurobarometers do not allow benchmarking comparisons among countries due to the low sample size (sample size per country varies between 13 to 58) [31, 32], while no data are available for adolescents under 15 years; (b) SB was measured by a single self-reported question from the IPAQ, which is likely to underestimate the sitting time of adolescents [51]. However, as suggested with older adults, the use of the IPAQ Short form in this study should be valid as we compare groups within and between years instead of on individual basis [52]; (c) it is important to note that the sitting question of the IPAQ short version from 2002 to 2005 was an open solution of the total sitting time in a weekday, whilst, from the 2013 onwards the possible answers were closed to several categorical response options [53]. Finally, the existing reports do not distinguish between SB pattern or where they occur (at the educative centre or out the educative centre). Thus, future Eurobarometer surveys might consider making an extra effort to 1) get enough representativity to allow both benchmark comparisons among European countries and strength the comparison analysis between girls and boys; 2) target other children population (i.e. pubertal, prepuberal or young children); 3) monitor the engagement on the most common sedentary activities for each under 18 years old group and be able to collect SB patterns; 4) monitor the sitting behaviour either at or out the educative centre.
Despite these limitations, it is important to consider that it is the first work to assess the prevalence trend of SB in adolescents among the European Union countries and provides an initial approach to the studied research question. It is expected that this initial approach provides a significant insight for European researchers, guideline developers, and policy makers in developing new strategies to address SB among European adolescents. Finally, this work has identified some limitations in Eurobaromenter reports that might be relevant to be addressed in future reports (e.g. low sample size or only adolescents are being monitored).