Background A systematic synthesis of findings on factors influencing ACP engagement should inform the development of innovative behaviour change interventions. The objectives of this review were to (a) identify all stakeholders` perspectives on facilitators and barriers to engagement in ACP behavioural outcomes among adults (≥50 years old) in community settings and (b) map the influencing factors across the Capability, Opportunity, and Motivation dimensions of behaviour (COM-B model).

Methods The study utilised a hybrid mixed-research synthesis approach and followed a published protocol. Content analysis was applied to the results section of the included studies. A systematic data transformation and triangulation processes underpinned findings integration.

Results The review included 117 records, mainly using qualitative approaches (86.3%). Studies included patients (62%), service providers (29%), and trusted persons/surrogates (9%). The behavioural focus was on the general ACP behavioural outcome (41%), communication (28.7%), documentation (22%), decision-making (5.3%), or surrogate appointment (3%). Ten categories of influencing factors were identified. They were ranked according to frequency of reporting and labelled as: Connectedness, Psychological Factors, Metapreferences, Service Provision, Temporality, Sociodemographic Characteristics, Literacy, Resources, Experience, and Macro-Level Factors. Each category was defined by meaningful sub-categories (52 in total), which were mapped across the COM-B model. The most frequently reported factors within the Motivation dimension of the COM-B were Comfort and Readiness (n=78), Actors and Roles Requirements (n=56), and Perceptions and Beliefs (n=45). The Opportunity dimension included Communication and Understanding (n=43), Effect of the Other (n=42), and Involvement and Collaboration (n=41). The top sub-category within the Capability dimension was ACP literacy (n=43).

Discussion The triangulation of stakeholders` perspectives facilitated identification a complex array of factors that influence engagement in ACP behaviours. Their mapping across the COM-B model pointed directions for future research, policy, and practice. It will also inform the design of an innovative and evidence-based ACP intervention.