Short summary

The political agreement to implement a new reform in Danish public schools in 2013 has resulted in a number of changes including a requirement for on average 45 minutes of physical activity (PA) each day.

The overall aim of the present study is to 1) examine the effectiveness of the '45 minutes of PA per day' initiative on PA, 2) examine the effectiveness of the '45 minutes of PA per day' initiative on body-mass index (BMI), and 3) describe variations of PA across diverse sociodemographic factors.

Rationale

Sedentary behavior and low levels of physical activity (PA) is a great threat to global mortality causing more than 3.2 million deaths yearly. Consequently, decreasing the prevalence of insufficient PA levels is one of WHO's top priorities in non-communicable disease prevention and control. A new report based on data from the Health Behavior in School-aged Children Study (HBSC) reported that 87% of Danish children aged 11-15 did not meet the Danish PA recommendations in 2014 emphasizing the importance of national PA promotion in children and adolescents.

Schools are considered an important setting for PA promotion and prevention of obesity, since children and adolescents spend considerable large amounts of time in school. In Denmark, the school-based approach has the additional advantage that the majority of Danish children and adolescents receive their primary education in public schools providing access to vulnerable sub-groups, such as the socioeconomically disadvantaged families. Consequently, the Danish Government has given a greater priority to PA in a new Danish school reform introduced in all municipal primary and lower secondary schools. The school reform was introduced in fall 2014 intending to entail a longer and more varied school day that alters between traditional educational activities and supporting educational activities such as projects, play and movement. One of the overall aims of the new reform has been to create the optimum conditions for all students to achieve their full learning potential by combining different activities and teaching methods. Thus, the supporting educational activities include a large range of diverse activities (including PA) that support the students in developing and strengthening their learning readiness, social competences, motivation and well-being. For a long time, two hours of physical education (PE) per week has been a mandatory part of the curriculum in the Danish Schools. As a part of the reform PE has been extended and added to the school leaving examinations in the 9th grade to emphasize the importance of PA in health. Moreover, the new reform has entailed that PA (not only as a part of PE) to a greater extent than before is an integrated part of the school day corresponding to an average of 45 minutes per day.

From 2011 and onwards it has been mandatory for school nurses to report height and weight on 6-7 and 14-15 year old school children to Børnedatabasen (BDB) making it possible to evaluate whether the PA initiative in the Danish public schools has affected BMI. However, no national surveillance of objectively measured PA exists. At University of Southern Denmark, however, data on objectively measured PA (measured by accelerometers) has been collected in numerous population-based research projects since 1998 providing data on objectively measured PA in children and adolescents before the introduction of the school reform. This available historical data on PA, Børnedatabasen and the introduction of the Danish school reform provide a unique opportunity for evaluating the effectiveness of an ambitious nationwide school-based health initiative, which is the overarching objective of the present project. The assessment of PA does, however, require data on PA after the introduction of the reform in 2014 for which reason a new data collection will be conducted in 2017/18. Additionally, this new large sample (completed with new accelerometer technology) makes it possible to describe highly accurate estimates of sedentary behavior in children and adolescents, which, as stated previously, is a great nationwide health hazard.

Description of the cohort

Evaluation of PA (Population 1)

PA data from four historical school-based population-based studies will be included in the present study to evaluate pre-legislation (before the introduction of the reform in 2014) PA levels and trends: 1) The European Youth Heart Study (EYHS) conducted in 1998, 2004 and 2010 (n=1875), 2) When Cities Move Children (WCMC) conducted in 2010 and 2012 (n=623), 3) Childhood Health, Activity and Motor Performance School Study Denmark (CHAMPS) conducted in 2009, 2010 and 2012 (n=515), and 4) School site, Play Spot, Active transport, Club fitness and Environment (SPACE) conducted in 2010 and 2012 (n=700). These four studies comprise the historic data on PA among approximately n=3800 1st to 9th grade children from 40 schools in 8 municipalities in the Region of Southern Denmark and the Capital Region of Denmark.

To be able to evaluate post-legislation PA levels, a new data collection will be conducted in fall 2017 to spring 2018. The assessment of PA in this upcoming data collection will be conducted in a sample representing the source population of the four historical studies. Consequently, the participants in the present study will be recruited at the same schools in the same year groups as in the historical projects. In Odense municipality we aim to recruit n=1000 3rd and 9th grade students representing the EYHS population. In Svendborg Municipality, we aim to recruit n=1000 1st to 6th grade students representing the CHAMPS population. In Copenhagen municipality we aim to recruit n=700 5th to 8th grade students representing the WCMC population. In Vejle, Varde, Esbjerg, Nordfyns and Sønderborg municipality we aim to recruit n=1400 5th to 8th grade students representing the SPACE population. Approximately n=4100 1st to 9th grade students will be recruited from approximately 40 public schools in 2017-18. A student is found eligible if he/she attends one of the public schools and classes in question, and if he/she does not suffer from any physical disabilities or injuries preventing the subject in being physical active on a level where the accelerometer is able to register movement.

Evaluation of BMI (Population 2)

Data on BMI will be collected from the Danish nationwide surveillance database Børnedatabasen (BDB). Since 2011, it has been mandatory for school nurses or pediatricians to annually assess weight and height on 6-7-year old children and 14-15-year old adolescents, and report data to BDB.

Data and biological material

Evaluation of PA (Population 1)

PA will be measured using objective activity monitors (accelerometers). Moreover, both the participants and their parents will complete a questionnaire gathering data on background variables, injuries, sports participation, screen-time etc. The questionnaires have not been fully developed yet. Data on the parents' education and ethnicity will be gathered via Danmarks Statistik.

Evaluation of BMI (Population 2)

These data will be gathered via BDB.

Collaborating researchers and departments

The projects is a collaboration between different research units at the Department of Sports and Clinical Biomechanics, University of Southern Denmark (Exercise Epidemiology, Centre of Research in Childhood Health, Active Living and FIIBL). 

The project is funded by TrygFonden.