Simulation methods

The HIIC quantifies intervention impacts through the use of proportional multistate lifetable (PMSLT) simulation modelling. The general methodology underpinning PSMLT techniques is outlined below, with a more detailed explanation available in Blakely et al. (2020).

Overview

PMSLT simulation modelling is a method for evaluating health and cost impacts of prevention policies, through the use of lifetables.Under PMSLT simulation approaches, lifetables are modified through interventions that alter disease incidence, morbidity, and fatality, which in turn affect population-level life-expectancy.

These modifications result in two scenarios:

1. business as usual (BAU) scenario: where disease incidence, morbidity, and fatality is not modified, in order to generate baseline outcome metrics to compare against the intervention scenario
2. intervention scenario: where disease incidence, morbidity, and/or fatality are modified, resulting in greater life-expectancy and modified outcome metrics

By analysing differences in mortality rate and life-expectancy between BAU and intervention scenarios, one may estimate the health, cost and productivity impacts generated by an intervention.

Lifetables

Lifetables are tables produced by governments and statistical agencies to estimate overall mortality rates of a certain population's entire lifetime. These estimates are broken down by sex and age, and enable estimation of the impact of potential changes to mortality rates in the future. An cohort example lifetable, adpated from Blakely et al. (2020), for 50-54-year-old New Zealand non-Maori males alive in 2011 is provided below.

Estimating intervention outcomes

Estimating health and cost impacts of an intervention requires simulation of seperate lifetables for BAU and intervention scenarios. For each model year, we compute the total excess number of individuals living in the intervention scenario