Modeling Sedentary Behavior Impact on Health

The ACE-Obesity Policy model is a proportional, multi-state, life table Markov model simulating the body max index (BMI), physical activity (PA) and fruit and vegetable consumption profile of the 2010 Australian population [22 ]. The model calculates the health adjusted life years (HALYs) saved as a result of an intervention’s effectiveness in improving any of the above risk factors for obesity, captured through reductions in prevalence of nine obesity-related diseases: breast cancer, endometrial cancer, kidney cancer, hypertensive heart disease, ischemic heart disease, stroke, T2D and osteoarthritis (hip and knee). The ACE-Obesity Policy model has been used in economic evaluations of multiple obesity prevention interventions [23 (link)–27 ], including two SB reduction interventions [22 ]. However, both these evaluations used the PA component of the model and estimated the changes in physical activity (resulting from increased standing measured using METs) arising from the SB intervention. One intervention in children assumed the resultant reduction in sitting time was equal to an increase in standing time [21 ]; the other workplace intervention modelled an increase in standing time [16 (link)]. The direct impact of SB on chronic disease was not estimated. Given that SB is not equivalent to physical inactivity, this current research sets out to more accurately estimate the impact of reductions in SB using epidemiological and economic modelling. The SB module allows the direct modelling of intervention outcomes through reductions in sitting time rather than increases in physical activity. The SB model will be integrated into the current ACE-Obesity Policy model to facilitate the comparative analysis of interventions with impacts on various risk factors.
The steps involved in developing and incorporating the SB risk factor model into the ACE-Obesity Policy model include: (1) assessment of the current Australian adult population exposure to sitting time; (2) a systematic review of the current literature to identify the associations between SB and incidence of chronic diseases, in particular the nine diseases included in the ACE-Obesity Policy model, and the conduct of a meta-analyses; and (3) translation of the reduction in population sitting time into decreases in disease incidence using potential impact fractions (PIF). The primary parameters of the existing ACE-Obesity Policy model such as population, all-cause mortality, disease inputs (incidence, prevalence and case fatality) and disease costs were updated from 2010 to 2019 values using various sources.