title: Health behavior change in advance care planning: an agent-based model.
abstract: BACKGROUND
  A practical and ethical challenge in advance care planning research is controlling and intervening on human behavior. Additionally, observing dynamic changes in advance care planning (ACP) behavior proves difficult, though tracking changes over time is important for intervention development. Agent-based modeling (ABM) allows researchers to integrate complex behavioral data about advance care planning behaviors and thought processes into a controlled environment that is more easily alterable and observable. Literature to date has not addressed how best to motivate individuals, increase facilitators and reduce barriers associated with ACP. We aimed to build an ABM that applies the Transtheoretical Model of behavior change to ACP as a health behavior and accurately reflects: 1) the rates at which individuals complete the process, 2) how individuals respond to barriers, facilitators, and behavioral variables, and 3) the interactions between these variables.
  
  
  METHODS
  We developed a dynamic ABM of the ACP decision making process based on the stages of change posited by the Transtheoretical Model. We integrated barriers, facilitators, and other behavioral variables that agents encounter as they move through the process.
  
  
  RESULTS
  We successfully incorporated ACP barriers, facilitators, and other behavioral variables into our ABM, forming a plausible representation of ACP behavior and decision-making. The resulting distributions across the stages of change replicated those found in the literature, with approximately half of participants in the action-maintenance stage in both the model and the literature.
  
  
  CONCLUSIONS
  Our ABM is a useful method for representing dynamic social and experiential influences on the ACP decision making process. This model suggests structural interventions, e.g. increasing access to ACP materials in primary care clinics, in addition to improved methods of data collection for behavioral studies, e.g. incorporating longitudinal data to capture behavioral dynamics.
authors.affiliation: Department of Health Policy and Management, University of North Carolina, Gillings School of Global Public Health, 1101 McGavran-Greenberg Hall, 135 Dauer Drive, Chapel Hill, NC, 27510, USA. ernecoff@live.unc.edu.
authors.forename: Natalie C
authors.initials: NC
authors.lastname: Ernecoff
authors.affiliation: Department of Behavioral and Community Health Sciences, University of Pittsburgh, Graduate School of Public Health, 130 DeSoto Street, Pittsburgh, PA, 15261, USA. crkcity@pitt.edu.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Keane
authors.affiliation: Department of Behavioral and Community Health Sciences, University of Pittsburgh, Graduate School of Public Health, 130 DeSoto Street, Pittsburgh, PA, 15261, USA. smalbert@pitt.edu.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Albert
mesh_terms: D032722:Advance Care Planning; D003657:Decision Making; D015438:Health Behavior; D006801:Humans; D008960:Models, Psychological