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Citation

McMillan L & Ford A (2025) A mixed methods process evaluation exploring the mechanisms through which an e-cigarette intervention produced changes in tobacco smoking behaviour among people accessing homelessness services. Society for Research on Nicotine and Tobacco (SRNT), New Orleans, USA, 12.03.2025-15.03.2025.

Abstract
Significance Around 80% of people experiencing homelessness smoke, yet the mechanisms that lead to smoking cessation among this population are not widely understood. Our cluster randomized controlled trial found that providing an e-cigarette starter kit in support centres for people experiencing homelessness was not an effective intervention for sustained abstinence at 24-weeks, however, significant reductions in tobacco smoking were reported. An embedded process evaluation aimed to explore the mechanisms through which the intervention produced changes in smoking behaviour. Methods The mechanisms of change (capability, opportunity, and motivation) were explored quantitatively via process measures in baseline and follow-up questionnaires and qualitatively via interviews with staff (n=16) and participants (n=32) in the intervention arm. We purposively sampled 8 centres (4 England, 2 Wales, 2 Scotland) within which to conduct the interviews. The centres varied according to factors such as centre size (i.e. number of daily attenders/residents), types of service provision (day centre/residential), staffing and services offered. Qualitative data was thematically analysed using deductive and inductive approaches. Quantitative measures were analysed descriptively. Data from the two approaches were combined for a detailed examination of the mechanisms of change. Results Participants demonstrated high levels of capability to use e-cigarettes and smoking reductions were widely reported. Knowledge of e-cigarettes and confidence to discuss smoking was enhanced by staff training. Opportunity was strengthened by social support, staff vaping, and increases in vaping acceptability, but unstable living situations, stress, alcohol and drug use, and environments high in smoking exposure hindered opportunity. Motivation was enhanced by financial benefits, strong beliefs in e-cigarette efficacy, and staff ‘buy-in’, but negatively impacted by adverse effects (e.g. coughing) and personal circumstances. Confidence and self-efficacy to quit were driven by cutting down behaviours and enhanced quitting beliefs for the future. Conclusions The delivery of an e-cigarette intervention can lead to positive behaviour change in smoking reduction by enhancing capability, opportunity, and motivation to use e-cigarettes among people experiencing homelessness.