Relationships between income inequality and health: an ecological Canadian study.
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Abstract Background: Many studies have demonstrated that health is a function of relative and not absolute income within populations. Canadian studies are not conclusive. There is a need for further investigation of the ‘relative income’ hypothesis in the Canadian population. Objectives: The primary objective of this research was to test the “relative income” hypothesis across Canadian health regions. The second objective was to extend the first hypothesis to consider rural versus urban populations in Canada. Methods: This research involved ecological analyses. The source of the data was the Canadian Community Health Survey, CCHS 2005 cycle 3.1. The units of analysis were health regions of Canada. Health of a region was estimated as the percentage of people who rated their health as good or excellent. The primary exposure variable was the ratio of people whose personal income was less than $15,000 relative to those reporting more than $80,000. Correlation analyses and multiple linear regressions were performed to ascertain the relationship between income inequality and health status in populations, adjusting for important covariates. Results: The measure of relative income inequality alone appeared to explain 18 per cent of the variability in the measure of health status in populations. However, after adding the measure of absolute income to the model, although 29 per cent of the variability was explained, the independent contribution of the inequality measure became non-significant. Linear regression models suggested that the absolute income variable alone could explain 30 per cent of the variance in the health status of populations. Other variables with a statistically significant contribution to the final multiple regression model were education and alcohol consumption. Rural/urban status did not change the individual relationship between relative income inequality or absolute income and the measure of health status in populations. Conclusion: Across Canadian health regions, health status in populations was a function of absolute income but not relative income. Regions with higher levels of education had better levels of self-rated health. A larger percentage of heavy drinkers was also correlated with lower population health status. The study findings have implications for public health, economic policies, and social policies.