# Applications of System Dynamics Models in Chronic Disease Prevention: A Systematic Review

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Figure 1 is a system dynamics model consisting of parts A, B, and C. Part A is a causal loop diagram in which a reinforcing loop shows the birth rate as a constant variable affecting births. The increase in births leads to an increase in population. In turn, an increase in population leads to an increase in births. A balancing loop shows increased deaths leading to decreased population, and an increase in the population in turn leading to increased deaths. In Part B, a stock-flow diagram shows population as the stock variable. Inflow births increase population (stock), and outflow deaths reduce population (stock). Births are affected by constantly variable birth rates at the same time, and outflow deaths are also affected by constantly variable mortality. C is a hybrid diagram in which population is the stock variable. Inflow births increase population (stock), and outflow deaths reduce population (stock). Births are affected by constantly variable birth rates at the same time, and outflow deaths are also affected by constantly variable mortality. Residual environmental carrying capacity (auxiliary variable) is affected by population and environmental carrying capacity (constant variable). Mortality (auxiliary variable) is affected by residual environmental carrying capacity and routine mortality (constant variable).

Figure 1.

System dynamics model in 3 parts showing the convergence of births and deaths to create population. The variables are linked by a causal chain with positive (+) and negative (–) polarity. The positive sign indicates that when variable A increases, variable B also increases; the negative sign indicates that when variable A increases, variable B decreases. The positive and negative signs represent either increase or decrease, not the proportional relationship between variables. Part A is a causal loop diagram that shows a reinforcing loop for increases in births and a balancing loop for deaths. Part B is a stock-flow diagram illustrating the convergence of birth rate and mortality rate, which equals population. Part C is a hybrid diagram that incorporates the effect of environmental carrying capacity, residual environmental carrying capacity, and routine mortality on births and deaths to result in population.

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In the identification phase, we initially retrieved 3,768 articles in January 2020 and 3,906 articles in February 2021. In the screening phase, after removing duplicate articles, 3,472 remained from the January 2020 search and 3,675 from the 2021 search. The title and abstract were screened again to determine if these articles met our criteria. After this second screening, 3,442 articles were excluded in 2020 and 3,655 articles were excluded in 2021. As a result, 30 articles in the January 2020 search and 20 articles in the February 2021 search remained. In the eligibility phase, after a full-text search of the 50 articles, 16 failed to meet the inclusion criteria and were removed (short communication, n = 4; conference papers, n = 9; no full-text, n = 3). Our review was based on the 34 remaining articles.

Figure 2.

Selection process for study of system dynamics models in chronic disease prevention, January 2000 to February 2021. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) diagram showing research study identification and selection process.

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Page last reviewed: December 23, 2021