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Confounding and Interaction

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Handbook of Epidemiology

Abstract

All epidemiological studies are (or should be) based on a particular source population followed over a particular risk period. The goal is usually to estimate the effect of one or more exposures on one or more health outcomes. When we are estimating the effect of a specific exposure on a specific health outcome, confounding can be thought of as a mixing of the effects of the exposure being studied with the effect(s) of other factor(s) on the risk of the health outcome of interest. Interaction can be thought of as a modification, by other factors, of the effects of the exposure being studied on the health outcome of interest and can be subclassified into two major concepts: biological interdependence of effects, which includes concepts of synergism and antagonism, and effect-measure modification, also known as heterogeneity of a measure across the levels of another factor. Both confounding and interaction can be assessed by stratification on these other factors (i.e., the potential confounders or effect-measure modifiers). This chapter covers the basic concepts of confounding and interaction and provides a brief overview of analytical approaches to these phenomena. Because these concepts and methods involve far more topics than we can cover in detail, we provide many references to further discussion beyond that in the present handbook, especially to relevant chapters in Modern Epidemiology by Rothman et al. (2008).

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Acknowledgements

The authors are grateful to Katherine J. Hoggatt and the editors for numerous helpful comments that improved this chapter. Funding for Neil Pearce’s salary is from a Programme Grant from the Health Research Council of New Zealand.

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Authors and Affiliations

  1. Department of Medical Statistics, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK

    Neil Pearce

  2. Centre for Public Health Research, School of Public Health, Massey University Wellington, Wellington, New Zealand

    Sander Greenland

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  1. Neil Pearce
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  2. Sander Greenland
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Editors and Affiliations

  1. Department of Epidemiological Methods and Etiologic Research, Leibniz Institute for Prevention Research and Epidemiology – BIPS, Bremen, Germany

    Wolfgang Ahrens

  2. Department of Biometry and Data Management, Leibniz Institute for Prevention Research and Epidemiology – BIPS, Bremen, Germany

    Iris Pigeot

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Pearce, N., Greenland, S. (2014). Confounding and Interaction. In: Ahrens, W., Pigeot, I. (eds) Handbook of Epidemiology. Springer, New York, NY. https://doi.org/10.1007/978-0-387-09834-0_10

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