Direct and indirect pathways between low income status and becoming a high-cost healthcare user in Ontario, Canada: a mediation analysis of health risk behaviors

Purpose — We investigated natural direct and indirect pathways between low income status and high-cost user (HCU) transitions considering health risk behaviors as potential mediators.

Methods — We analyzed data from respondents (aged 18+) from four pooled cycles of the Canadian Community Health Survey (2005-2010/2011) linked to administrative data in Ontario, Canada. HCUs were defined as the top 5% of the population, ranked by cost consumption in any of the five years following survey interview. Low income status was defined from the provincial distribution of self-reported household income, with missing values imputed from neighborhood-level data. In mediation analyses based on marginal structural models, we quantified the contributions of smoking, physical inactivity, alcohol consumption and body-mass index (BMI) to income-HCU associations.

Results — 115,091 respondents (representative of 9,661,764 Ontarians) were included in the study, of which 7.2% became HCU. The odds of becoming HCU were 1.36 times (95% CI: 1.25-1.48) greater for low (vs. high) income status respondents. Smoking, physical activity, alcohol consumption and BMI contributed 9.4%, 6.5%, 10.6% and 4.4% to this association, respectively. Tests for exposure-mediator interactions were not statistically significant.

Conclusions — Health risk behaviors only partially explain income inequalities in future HCU transitions.