Accurate assessment of the association between exposure and response is central to identifying causality in medical research.
The concentration index has been commonly used to study income inequality and socioeconomic related health inequality.
This study generalizes applications of the concentration index to measure the relative and attributable risks for describing
exposure-response relationships in medical research. Based on cumulative distribution functions, a new measure of correlation
is proposed to quantify the association between exposure and response. The connection between the new and existing measures
is discussed. The method enables the semi-parametric analysis of overall association and disparity by risk factors. Both grouped
and continuous data situations are considered with two applications. The first example illustrates the relationships between the
concentration index, relative and attributable risks. The second example demonstrates how the concentration index can assist in
evaluating the association between the radiation dose and the incidence of leukaemia. Logistic regression based decomposition
is compared with the new approach. We found the concentration index analysis useful not only for examining socioeconomic
determinants of health, but also for assessing quantitative relations between exposures to health risks and ill-health outcomes.
Yuejen Zhao is the Principal Health Economist of Department of Health, Northern Territory, Australia. He is an adjunct senior research fellow
at Charles Darwin University and Flinders University. He has a bachelor degree of medicine, a master degree of biostatistics and a Ph.D. in
mathematics. His research interests are in medical statistics, epidemiology and health economics.
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