HealthPaths Dynamics – Using Functional Health Trajectories to Quantify Impacts on Health-Adjusted Life Expectancy (HALE) in Canada Seminar

It is a commonplace that there is significant dispersion in health status in populations, as well as a strong correlation between health status and socio-economc status. However, there remains considerable uncertainty as to the quantitiative importance of various causal factors in accounting for these health inequalities. Since health status is intrinsically a reflection of co-evolving dynamic processes, it is essential to employ an analytical framework that brings together robust estimates of individuals’ health status as functions of health determinants dynamics in order to assess realistically the sources of health inequalities.

This analysis is based the Health Utilities Index (HUI), a widely used summary index of an individual’s functional health, where the index is computed as a non-linear function of eight distinct categorical attributes – vision, hearing, speech, mobility, dexterity, cognition, emotion, and pain. The complex dynamics of HUI in a representative sample have been observed with Statistics Canada’ National Popultation Health Survey (NPHS) every two years since 1994.

The analysis begins with estimates of multivariate functional health trajectories, conditional on co-evolving risk factors. It then uses longitudinal microsimulation, drawing on the estimated system of equations for the dynamic relationships among the eight HUI components and major health determinants – including obesity, smoking, educational attainment, and a relatively little used psycho-social variable, Antonovsky’s Sense of Coherence The microsimulation process is used to synthesize a realistic base case representative longitudinal population sample, and then a series of carefully constructed counter-factual populations. Comparisons of the distributions of health-adjusted life lengths and summary HALE measures between counter-factuals and the base case are then used to estimate the quantitative importance of the major factors in accounting for HALE in Canada.