Exploring the Theory-Practice Gap in Public Health interventions: a critical assessment of the potential for Normalisation Process Theory to aid knowledge transfer into practice, using the evaluation of a complex smoking cessation in pregnancy initiative
: Exploring the Theory-Practice Gap in Public Health interventions

Student thesis: Doctoral Thesis


This thesis arises from the observation that complex interventions in public health, even when devised from high-quality, trial-based evidence, often fail to achieve expected outcomes and impact in practice. Data from a process evaluation of the implementation of a stop smoking in pregnancy initiative were used to explore this theory-practice gap, using Normalisation Process Theory (NPT). The aim of the thesis is to examine the utility of NPT in understanding both this gap and the challenges to implementing evidence-based, complex, public health interventions.
North East England is an area with high levels of smoking at time of delivery, (around 20%) when compared to national figures (average around 13%) at commencement of the study in 2012. Good evidence-based advice exists to address this issue (NICE, 2010) but local maternity staff had struggled to implement it. This led to the implementation of the example intervention, babyClear©, a package of measures which included standardising: carbon monoxide monitoring, opt-out referral to stop smoking services, enhanced follow-up and a risk perception tool.
NPT showed promise as an analytical tool, since it focuses on eliciting the implementation process of an intervention, and its feasibility and sustainability in context. A logic model was used to hypothesise the intervention process, which was subsequently compared with the findings from a thematic analysis, followed by analysis of the intervention and implementation using NPT.
NPT proved sufficiently flexible to use summatively in the evaluation cycle. Elements of the theory-practice gap, largely overlooked in trials evidence, were elucidated through clarifying other active ingredients and mechanisms of delivery. Environmental contexts were not completely captured by NPT. Data on sustainability and transferability were limited; however, it was found that NPT can identify factors that are likely to influence them. There were some challenges associated with using NPT, and core concepts required redefining to translate and adapt them for use in this study.
In conclusion, NICE Public Health Guidance (2010) is principally based on evidence from trials and would benefit from being combined with knowledge derived from research based on social theories, such as NPT. Routinely incorporating NPT, or similar, should be considered when implementing trial-based interventions into complex, public health systems.
Date of Award1 May 2020
Original languageEnglish
Awarding Institution
  • Teesside University
SupervisorSharon Hamilton (Supervisor), Janet Shucksmith (Supervisor) & Anna Van Wersch (Supervisor)

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