Evaluation of complex workplace dietary interventions

Background and aim The workplace has been identified as an ideal setting in which to promote healthy dietary behaviours. However, uncertainty surrounds both the effectiveness and costeffectiveness of workplace dietary interventions and a dearth of evidence exists with regards to evaluating the implementation process of such interventions. The core aim of this thesis was to conduct both a process evaluation and an economic evaluation of the Food Choice at Work (FCW) complex workplace dietary intervention. Methods The FCW study was a pragmatic trial which measured the effectiveness of a complex workplace dietary intervention in ideal settings. Firstly, a cross-sectional analysis which employed a zero-inflated negative binomial (zinb) regression model to examine associations between objective health status outcomes, lifestyle characteristics and absenteeism was conducted. Secondly, a detailed process evaluation addressed the implementation of the complex workplace intervention. Interviews were conducted at baseline (27 interviews) and at 7-9 months follow-up (27 interviews) with a purposive sample of workplace stakeholders (managers, caterers and employees). Data were analysed using a thematic framework. Thirdly, micro-costing methods were employed to estimate the cost of implementing and delivering the complex workplace dietary intervention from an employer’s perspective. Finally, an economic evaluation of the complex workplace intervention was conducted. This consisted of 1) a baseline costutility analysis (CUA) which measured the cost-effectiveness of the interventions in terms of quality-adjusted life-years (QALYs), 2) sensitivity analyses to test the robustness of the QALYs which involved performing cost-effectiveness analyses (CEA) using clinical measures to measure health outcomes and 3) a cost-benefit analysis (CBA) where the monetary value of absenteeism was employed so as to report the net benefit of the interventions relative to the control. Results Central obesity was positively associated with absenteeism and increased the expected rate of absence by 72% (mean number of absences was 2.5 days). Consuming a highquality diet and engaging in moderate levels of physical activity were negatively associated with absenteeism and reduced the expected frequency by 50% and 36% respectively. The process evaluation revealed that managers’ desire to improve company image, stakeholder buy-in, organisational support and stakeholder cohesiveness facilitated the implementation of the interventions. Anticipation of employee resistance towards menu changes, workplace restructuring and target-driven workplace cultures were found to impede intervention implementation. With regards to the cost-analysis, 3 main cost categories were identified 1) set-up costs 2) maintenance costs and 3) physical assessment costs. The combined intervention xvi reported the highest total costs (€47,305), followed by nutrition education (€44,726), environmental modification (€24,474) and the control (€21,412). In the economic evaluation, the baseline CUA indicated that each intervention (education (€970/QALY) environment (€98/QALY) and combined (€2,156/QALY)) can be considered costeffective when compared to the control. The CEACs demonstrated that the uncertainty in the incremental costs and effects translated into decision uncertainty for the environment intervention (50% probability of being cost-effective at €45,000/QALY threshold). However, at no point between a ceiling ratio of €0 to €100,000/QALY did the education and combined interventions have a higher probability of being cost-effective than the control. The results of the secondary CEA confirm the baseline CUA results for each intervention. The environment intervention reported the lowest ICERs for: BMI (€14/kg/m2 ), midway waist circumference (€3/cm) and weight (€7/kg). Furthermore, the environment intervention offers the highest net benefit for employers with a positive net benefit of €145.82 per employee reported. Conclusion This thesis provides critical evidence on the relationship between obesity, adverse lifestyle factors and absenteeism. Furthermore, findings also indicate that environmental modification strategies have the potential to offer a cost-effective approach for improving employee health outcomes, depending on the perspective taken. This thesis also highlights the importance of considering contextual factors such as workplace structures and cultures in the development and implementation of future workplace dietary interventions