Module on Confounding by Population Stratification

This learning module, created by the UW Center for Genomics and Public Health, is intended to provide an understanding of basic concepts in genetic epidemiology.

This tool, meant primarily for epidemiologists, can be adapted for discussion among public health professionals and students interested in learning more about genetic epidemiology.

Educational Objectives

After viewing this guided reading, you should be able to:

  • Describe what is meant by population stratification.
  • Understand the conditions under which population stratification can occur.
  • Discuss how population stratification may affect the interpretation of case-control genetic association studies.
  • Be familiar with the methods used to address population stratification.

Guided Reading

Using the classic study by Knowler et al., we will detail how population stratification can confound the relationship between a genetic marker and disease. We will discuss how population stratification can affect the results and interpretation of a genetic association study. Finally, we will list recent review papers that address this issue in more detail. This module assumes that the reader has read the article below.

Knowler WC, Williams RC, Pettitt DJ, Steinberg AG. Gm3;5,13,14 and type 2 diabetes mellitus: an association in American Indians with genetic admixture. Am J Hum Genet 1988;43(4):520-6. (PubMed Link)*If you are having trouble accessing this article, please contact us.

Selected Documents

Cardon LR and LJ Palmer. Population stratification and spurious allelic association. Lancet 2003;361:598-604. (PubMed Link)

Thomas DC and JS Witte. Point: population stratification: a problem for case-control studies of candidate-gene associations? Cancer Epidemiol Biomark Prev 2002;11:505-12. (PubMed Link)

Wacholder S, Rothman N, Caporaso N. Counterpiont: bias from population stratification is not a major threat to the validity of conclusions from epidemiological studies of common polymorphisms and cancer. Cancer Epidemiol Biomark Prev 2002;11:513-20. (PubMed Link)

Ziv E and EG Burchard. Human population structure and genetic association studies. Pharmacogenomics 2003;4:431-41. (PubMed Link)

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