Evaluating changes and predictors of intention to act on health in urban development: a single-arm pre-post mixed-methods study of the changing mindsets intervention

Background: The built environment contributes to rising non-communicable diseases, including cancer, diabetes, respiratory illness, and poor mental health. These impacts disproportionately affect lower socio-economic groups, who experience greater exposure to harmful urban features. Evidence on these links alone has not led private-sector urban developers to prioritise health. The Changing Mindsets intervention was designed to increase intention to act on health and health inequalities among private-sector urban development professionals. This study assessed whether the intervention increased intention to act and identified predictors of change. Methods: We conducted a single-arm pre-post mixed-methods evaluation of the Changing Mindsets intervention delivered at six industry events in 2024, including four in-person and two online sessions. The intervention combined an industry-partner-led presentation, peer discussion, and a supporting website. Surveys were completed immediately before (T1), immediately after (T2), and three-months after the intervention (T3). Paired analyses assessed pre-post change in intention to act. Logistic regression examined predictors of improvement from T1 to T2. Seven participants completed follow-up interviews exploring changes in thinking and actions taken. Results: Of 156 attendees, 101 completed the T1 survey, 69 completed the T2 survey, and 22 completed the three-month follow-up. Immediately after the intervention, 19% of participants showed an increase in intention to act on health, while most showed no change. Paired analyses indicated a small increase in mean intention scores from T1 to T2, with limited evidence of a consistent group-level effect. Lower baseline intention and increased perceived psychological proximity to health issues were associated with improvement in intention to act. Mean intention scores remained elevated at three-months among respondents. Qualitative findings suggested that changes in thinking were linked to challenged assumptions about who can act on health. Reported actions most often involved initiating conversations and influencing others. Conclusions: The Changing Mindsets intervention was associated with increased intention to act on health among a subset of urban development professionals, particularly those with lower baseline intention and greater perceived proximity to health issues. Evidence for a strong average pre-post effect was limited. However, intention remained elevated at three-month follow-up among respondents, suggesting retention of motivation over time. Trial registration: ISRCTN12310546 registered on the 30th March 2021.