The impact on children's bone health of a school-based physical education program and participation in leisure time sports: The Childhood Health, Activity and Motor Performance School (the CHAMPS) study, Denmark
Introduction
The peak bone mass (PBM) is the maximum attained bone mass in a lifetime. A low PBM is a predisposing factor to later development of osteoporosis (Bachrach, 2001). Several factors affect the magnitude of the PBM such as genetics, and lifestyle including nutrition and physical activity (PA) (Berger et al., 2010, Fewtrell et al., 2009). It is important to optimize the modifiable factors during childhood and adolescence when bone growth occurs in order to achieve the highest possible PBM according to our genetic potential, since low bone mass in elderly people is associated with a high fracture risk (Johnston and Slemenda, 1994). The optimal time for bone mineral accrual is pre-puberty and early puberty (Bass et al., 2002).
Adiposity and inactivity in childhood is an increasing problem in high-income countries (Brisbois et al., 2012). The impact of adiposity on bone health in childhood and adulthood is contradictory (Dimitri et al., 2012). However, as commonly known inactivity is highly correlated to adiposity and has a negative impact on bone health and may cause a lower PBM and a later increased risk of osteoporosis. The behavior of inactivity tracks from early childhood into adulthood (Janz et al., 2005) and it is important to influence children's behavior of physical activity at an early stage in life to ensure future health and good habits of PA.
The objective of the study was to evaluate the effect of a generalized school based PE program on children's bone health, and to examine if participation in leisure time sport (LTS) influences the impact of school type on children's bone health or has an independent impact on bone health in childhood.
Section snippets
Study design
The study was a part of the CHAMPS study, DK an on-going prospective observational cohort study (Wedderkopp et al., 2012). The CHAMPS-study, is a natural experiment, in which the variations in exposure (i.e. the sports schools versus the traditional schools) and outcomes are analyzed with the intent of making causal inferences (Craig et al., 2012) on the effect of the intervention.
Nineteen primary schools in the municipality of Svendborg, Denmark, were invited to participate in the project, six
Anthropometrical data
Anthropometric measures were measured with children required to go barefoot, wearing only a thin T-shirt, underwear and stockings. Body weight was measured to the nearest 0.1 kg on an electronic scale, SECA 861, and height was measured to the nearest 0.5 cm using a portable stadiometer, SECA 214 (both from Seca Corporation, Hannover, MD).
Dual energy X-ray absorptiometry
Dual energy X-ray absorptiometry (DXA), GE Lunar Prodigy (GE Medical Systems, Madison, WI), equipped with ENCORE software (version 12.3, Prodigy; Lunar Corp,
Results
The children attended 2nd to 4th grade (7.7–12 years) at baseline (2008). Of these, 742/800 (93%) accepted to participate and 682/742 (92%) participated at follow-up (47% boys, and 53% girls). The characteristics of the participants at baseline and at follow are reported in Table 1, Table 2. There were no differences in the participant's height, weight, or DXA values, or in the distribution of pubertal stages between the two school types.
The relationship between school-type and BMC, and BMD and
Discussion
In this longitudinal study we examined the effect of a school based PE program and the effect of participation in LTS on children's bone health. LTS had a positive impact on bone accrual in children with boys having the greatest effect from LTS regardless of school type. The analyses revealed no effect of school type on children's bone mineral accrual during the two-year observation time. The hypothesis of a positive effect on bone traits of the sports schools for children with low amount of
Limitations and strength
Our study had some limitations. The creation of sports schools was a political decision in the municipality of Svendborg therefore the design was not a randomized controlled trial but a natural experiment (Craig et al., 2012). Children in the two groups were however, comparable at baseline regarding all measurements presented in this article. Information on the children's PA level at baseline was not available. It is not possible to conclude that the patterns of activity were equal at the
Conclusion
In conclusion there was a highly significant positive relationship between participation in LTS and bone health. There was no impact on bone health (TBLH and lower limb) for children attending sports schools compared to children in traditional schools.
Conflict of interest statement
The authors declare that there are no conflicts of interests.
Acknowledgments
The authors gratefully acknowledge the work of numerous students and PhD students who have participated in the data collection for the CHAMPS study — DK. We thank children, parents and teachers in the schools involved in the project, and we are grateful for the cooperation of “Elitesekretariatet” in the municipality of Svendborg. The study would have not been possible without financial support from the Nordea Foundation, the TRYG Foundation, the IMK Foundation, the Region of Southern Denmark,
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