Background
Public health interventions are often promoted without strong evidence of effectiveness in real-world settings. In England there is a vast amount of routine data available that can be used to evaluate these interventions. Less than 50% of children in England meet the government’s physical activity guidelines, which is a major public health concern. Simple, effective interventions for all are required to tackle shortfalls in children’s physical activity. The Daily Mile (TDM) is a school-based active mile intervention that has been widely adopted to address this shortfall. This thesis aims to use routine data to evaluate a real-world public health intervention by assessing the reach, impact, and fidelity of TDM.

Methods
This thesis comprises four cross-sectional studies linking various health, education, and census data. In the first study, I created a database of all state-funded primary schools in England and used multilevel models to determine the association between school and local authority characteristics, and registration to TDM. In the second study, I conducted a hierarchical cluster analysis to group local authorities by ‘need’ and estimated the association between ‘need’ and registration to TDM. In the third study, I used self-reported physical activity data to compare minutes of MVPA, and the variety of activities reported per week between children attending TDM-registered and non-TDM registered schools. Finally, I assessed fidelity to TDM’s core running criteria among children registered using descriptive statistics and multilevel models.

Results
TDM is a wide-reaching intervention with one in five primary schools in England registered. Schools in urban areas and schools with a higher proportion of disadvantaged pupils were more likely to register. TDM appears to be an equitable intervention reaching schools in areas of highest need; registration ranged from one in five schools in low-need areas to one in four in high-need areas. Children attending schools registered to TDM reported a marginally greater variety of activity and 10 additional minutes of MVPA/week during school hours and 26 additional minutes of MVPA/week outside school hours compared to children in non-TDM schools. Fidelity of implementation to TDM remained low, where 30% of those registered reported adhering to TDM’s core running criteria.

Conclusion
This thesis demonstrates that routine data can effectively be used to evaluate real-world public health interventions. TDM is a wide-reaching intervention and appears to be equitable. However, it does not seem to impact children’s physical activity substantially, and implementation remains low. TDM must be embedded within a broader suite of interventions to increase children’s physical activity.