The degree to which social inequalities affect a population's health has been an ongoing debate for many years. A recent study found that one measure of social inequality, wage inequality, is associated with the infant mortality rate (IMR) in 19 wealthy countries belonging to the Organization for Economic Cooperation and Development (OECD). The study was supported in part by the Agency for Healthcare Research and Quality (National Research Service Award training grant T32 HS00029).
For the study, researchers used data from the OECD, World Value Surveys, Luxembourg Income Study, and political economy databases to assess the impact of health system variables on the relationship between wage inequality and infant mortality in 19 OECD countries between 1970-1996. Overall, IMR declined from a mean of 16.6 per 1,000 in the 1970s to 6.2 per 1,000 in the 1990s. The Theil measure of wage inequality was positively and significantly associated with IMR, even while controlling for gross domestic product (GDP) per capita, the most powerful ecological predictor of infant mortality. The Theil measure is based on industrial sector wages; a higher Theil value means higher levels of wage inequality.
After controlling for GDP per capita and wage inequality, variables generally associated with better health included higher income per capita, the method of health care financing, and more physicians per 1,000 population. Higher alcohol consumption, a larger proportion of the population in unions, and more government expenditures on health were associated with poorer health outcomes. Results suggest that improving aspects of the health care system, particularly equitable health care financing and more physicians, may be one way to partially compensate for the negative effects of social inequalities on population health.
See "Wage inequality, the health system, and infant mortality in wealthy industrialized countries, 1970-1996," by James A. Macinko, Ph.D., Leiyu Shi, M.B.A., Dr.P.H., and Barbara Starfield, M.D., M.P.H., in Social Science & Medicine 58, pp. 279-292, 2004.
Editor's Note: A literature review by the same group of researchers showed that the relationship between income inequality and health is unclear. For more details, see Macinko, J.A., Shi, L., Starfield, B., and Wulu Jr., J.T. (2003, December). "Income inequality and health: A critical review of the literature" (AHRQ grant T32 HS00029). Medical Care Research and Review 60(4), pp. 407-452.