The Conceptual HABITS Prototype for Integrating Behavioural Theories with System Dynamics and Agent-Based Models to Capture Complex Health Behaviours

Healthcare simulation models often rely on oversimplified assumptions about health behaviour, potentially undermining their predictive power and policy relevance. This paper systematically reviews how behavioural theories have been incorporated into healthcare simulation models and proposes HABITS (Health Behaviour Integrated Theory-based Simulation), a conceptual prototype combining advances in simulation modelling and behavioural science. Our research reveals that current approaches suffer from ad-hoc theory selection, overemphasis on behaviour change initiation over maintenance, and neglect of crucial areas, including health systems management, non-communicable-disease self-management, and provider behaviours. Most studies target motivation and opportunity drivers of health behaviour while overlooking capacity enhancement and broader social determinants. HABITS is designed to address these limitations by integrating the COM-B (Capability, Opportunity, Motivation-Behaviour) model with hybrid simulation approaches, providing structured guidance for incorporating behavioural determinants across system, social, and individual levels while capturing between-level feedback. This integration enables operationalisation of the Behaviour Change Wheel, allowing systematic development and evaluation of interventions and policies. This prototype aims to enhance design transparency, facilitate cross-study comparisons, and improve communication across disciplines and with stakeholders. Future research should explore theory-data integration and synergies between behavioural theories and emerging technologies such as Large Language Models to develop more robust, predictive models. When organisations use computer models to plan healthcare services or design public health interventions, they often make overly simple assumptions about how people behave. For example, models may assume that once someone adopts a healthy behaviour, such as taking medication regularly or increasing physical activity, they will simply continue doing so. In reality, human behaviour is far more complex, and these simplifications can lead to policies that look promising on paper but underperform in practice. This paper reviews how researchers have tried to incorporate knowledge from behavioural science into healthcare simulation models, and identifies significant gaps in current practice. In particular, existing models tend to focus narrowly on what motivates people to change behaviour in the first place, while ignoring the skills, resources, and social environments needed to sustain that change over time. To address this, we propose HABITS (Health Behaviour Integrated Theory-based Simulation), a practical framework that helps modellers build more realistic and comprehensive representations of health behaviour. HABITS draws on established behavioural science to guide decisions about which factors to include in a model, from individual psychology to social influences and healthcare system structures, and how these factors interact with one another. For practitioners and policy makers, the main value of HABITS is that it offers a clearer and more transparent way to design simulation models that better reflect real-world behaviour. This can improve communication between disciplines, support more credible policy analysis, and help identify interventions that are more likely to work in practice.