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01.12.2015 | Research article | Ausgabe 1/2016 Open Access

BMC Public Health 1/2016

The Active for Life Year 5 (AFLY5) school-based cluster randomised controlled trial: effect on potential mediators

BMC Public Health > Ausgabe 1/2016
Debbie A. Lawlor, Laura D. Howe, Emma L. Anderson, Ruth R. Kipping, Rona Campbell, Sian Wells, Catherine R. Chittleborough, Tim J. Peters, Russell Jago
Wichtige Hinweise

Electronic supplementary material

The online version of this article (doi:10.​1186/​s12889-016-2734-5) contains supplementary material, which is available to authorized users.

Competing interests

RC is a Director of DECIPHer IMPACT a not-for-profit company owned by the Universities of Bristol and Cardiff which licences and supports the implementation of evidenced-based health promotion programmes. Other authors declare they have no competing interests.

Authors’ contributions

DAL, RRK, RC, CRC, TJP and RJ designed the study AFLY5 study and obtained funds for it to be undertaken. SW managed the AFLY5 study. DAL, LDH, TJP and RJ designed the mediation study and identified the tools for assessing mediators. DAL wrote the analysis plan used for the mediation analyses presented in this paper and LDH and ELA completed all analyses. DAL, LDH and ELA wrote the first draft of the paper and DAL coordinated contributions from other co-authors. RRK, RC, SW, CRC, TJP and RJ all made critical comments on drafts of the paper. All authors read and approved the final manuscript.



Active for life year 5 (AFLY5) is a school-based intervention, based on social cognitive theory, which aims to promote healthy levels of physical activity and healthy eating by improving a child’s self-efficacy to make healthy choices, their knowledge of how to make such choices and prompting parents to support their children to make healthy choices. Previously published results showed no effect on the three primary outcomes and beneficial effects on three of nine secondary outcomes (time spent screen-viewing at weekends, consumption of snacks and of high energy drinks). This paper aims to determine the effect of the intervention on potential mediators.


We conducted a cluster RCT of a school-based intervention, with allocation concealed by use of a remote system. The study was undertaken in the South West of England between 2011 and 2013. Participants were school children who were age 8–9 years at baseline assessment and 9–10 years during the intervention. Potential mediators were assessed at the end of the intervention. The intervention consisted of teacher training, provision of all materials required for lessons and homeworks and written materials for school newsletters and parents. The ten potential mediators were child-reported self-efficacy for physical activity and fruit and vegetable consumption, perceived parental logistic support and modelling for their child’s physical activity, parental efforts to limit their child’s sedentary behaviour and modelling of healthy fruit and vegetable consumption, together with a knowledge assessment.


We successfully recruited 60 schools with over 2,221 children; valid data for the 10 mediators were available for 87 % to 96 % of participants. Three of the ten potential mediators were greater in the intervention, compared with the control group: fruit and vegetable self-efficacy 2.2 units (95 % CI: 0.7 to 3.8), assessed on a scale 26 to 130; child-reported maternal limitation of sedentary behaviour 0.5 (0.1 to 0.8), scale 4 to 16; and knowledge 0.5 (0.2, 0.7) scale 0 to 9. Reported maternal limitation of sedentary behaviour and the child’s knowledge explained 23 % of the effect of the intervention on reducing time spent on sedentary behaviour at the weekend. There was no effect on other mediators.


Our findings suggest that the effect of the AFLY5 intervention on reducing screen-viewing at weekends was partially mediated by an effect on mothers limiting their child’s time spent sedentary and on increasing the child’s knowledge about healthy behaviour. However, overall our findings suggest that theory driven interventions, like AFLY5, can fail to influence most potential mediators and this may explain the failure of the intervention to improve most primary and secondary outcomes.

Trial registration

Current Controlled Trials ISRCTN50133740. Registered 17/03/2011
Additional file 1: Table S1. Main analyses of the effect of AFLY5 intervention on potential mediators assessed immediately after the end of the intervention, compared to a sensitivity analysis excluding those with high levels of missing data. Table S2. The main effect of the intervention on the three secondary outcomes found to be affected by the intervention, both before and after adjustment for potential mediators, and after excluding participants with high levels of missing data for potential mediators. Appendix. Knowledge assessment devised by study team. (DOCX 114 kb)
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