A Multilevel Analysis

Objective: To examine the association of income inequality at the public health unit level with individual health status in Ontario. Methods: Cross-sectional multilevel study carried out among subjects aged 25 years or older residing in 42 public health units in Ontario. Individual-level data drawn from 30,939 respondents in 1996-97 Ontario Health Survey. Median area income and income inequality (Gini coefficient) calculated from 1996 census. Self-rated health status (SRH) and Health Utilities Index (HUI-3) scores were used as main outcomes. Results: Controlling for individual-level factors including income, respondents living in public health units in the highest tercile of income inequality had odds ratios of 1.20 (95% CI 1.04-1.38) for fair/poor self-rated health, and 1.11 (95% CI 1.01-1.22) for HUI score below the median, compared with people living in public health units in the lowest tercile. Controlling further for median area income had little effect on the association. Conclusion: Income inequality was significantly associated with individual self-reported health status at public health unit level in Ontario, independent of individual income. MeSH terms: Income distribution; Health Status Index Studies of income distribution and health have been carried out in many industrialized nations,1-7 with mixed conclusions. In the United States, income inequality has consistently been found to be associated with health indicators such as mortality rates,8-10 and mechanisms through which income inequality may affect people’s health have been proposed.10 However, recent studies within other nations, including Canada,7,11,12 Japan,6 and New Zealand,3 did not support the association. It is not clear why the association exists in some societies but not in others. Although no significant effect of income inequality on health has been found in Canada, income inequality has been increasing in the past generation.13 We hypothesized that the increasing income gaps in Canada may have effects on Canadians’ health. We examined the independent effect of income inequality at the public health unit (PHU) level on individual health as measured by self-rated health status (SRH) and the Health Utilities Index (HUI), after adjusting for an individual’s income and other characteristics by using a multilevel analysis of Ontario Health Survey (OHS) data.