Mechanisms of implementing public health interventions: a pooled causal mediation analysis of randomised trials

Session: 

Oral session: Understanding and using evidence (2)

Date: 

Monday 17 September 2018 - 14:30 to 14:40

Location: 

Carrick 3

All authors in correct order:

Lee H1, Hall A2, Nathan N2, Reily K2, Seward K2, Williams C2, Yoong S2, Finch M2, Wiggers J2, Wolfenden L2
1 University of Oxford, United Kingdom
2 University of Newcastle, Australia
Presenting author and contact person

Presenting author:

Hopin Lee

Contact person:

Hopin Lee
Abstract text
Background:
The World Health Organization recommends that nations implement evidence-based nutritional guidelines and policies in settings such as schools and childcare services to improve public health nutrition. Understanding how implementation strategies exert their effects could enhance guideline implementation.

Objectives:
The aim of this study was to assess the mechanisms by which implementation strategies improved schools' and childcare services' adherence to nutrition guidelines.

Methods:
We conducted a mechanism evaluation of an aggregated dataset generated from three randomised controlled trials conducted in schools and childcare services in Australia. Each trial examined the impact of implementation strategies that targeted the knowledge, skills, professional role and identity, environmental context and resources of canteen managers. We pooled aggregated organisation level data from each trial, including quantitative assessments of the proposed mediators, as well as measures of school or childcare nutrition guideline compliance, the primary implementation outcome. We used causal mediation analysis to estimate the mediating effects.

Results:
We included 121 schools or childcare services in the pooled analysis; 79 were allocated to receive guideline and policy implementation strategies and 42 to usual practice. Overall, the interventions improved compliance (odds ratio 6.64, 95% confidence interval (CI) 2.58 to 19.09); however, the intervention effect was not mediated by any of the four targeted factors (average causal mediation effects through knowledge -0.00, 95% CI -0.05 to 0.04; skills 0.01, 95% CI -0.02 to 0.07; professional role and identity 0.00, 95% CI -0.03 to 0.03; and environmental context and resources 0.00, 95% CI -0.02 to 0.06). It is possible that the interventions were operating via alternative mechanisms that were not captured by the constructs we explored.

Conclusions:
Even though public health implementation strategies led to meaningful improvements in school or childcare nutrition guideline compliance, these effects were not explained by key determinants of successful implementation.

Patient or healthcare consumer involvement:
We sought involvement from stakeholders (school and childcare staff) during the elicitation of guideline implementation barriers and strategy development.

Relevance to patients and consumers: 

Schools and childcare services should implement nutritional guidelines to reduce the risk of dietary related chronic diseases. Three trials from Australia showed that an implementation strategy improved the uptake of evidence-based nutritional guidelines. To inform policy makers at schools and childcare services (consumers), we tried to understand how these implementation strategies work. We found that improving the knowledge and skills of canteen managers did not explain how the intervention worked. This indicates that policy makers may not want to focus on these targets when implementing nutritional guidelines.