1. Epidemiology and Global Health
  2. Genetics and Genomics
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Demographic history mediates the effect of stratification on polygenic scores

  1. Arslan A Zaidi  Is a corresponding author
  2. Iain Mathieson  Is a corresponding author
  1. University of Pennsylvania, United States
Research Article
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Cite this article as: eLife 2020;9:e61548 doi: 10.7554/eLife.61548


Population stratification continues to bias the results of genome-wide association studies (GWAS). When these results are used to construct polygenic scores, even subtle biases can cumulatively lead to large errors. To study the effect of residual stratification, we simulated GWAS under realistic models of demographic history. We show that when population structure is recent, it cannot be corrected using principal components of common variants because they are uninformative about recent history. Consequently, polygenic scores are biased in that they recapitulate environmental structure. Principal components calculated from rare variants or identity-by-descent segments can correct this stratification for some types of environmental effects. While family-based studies are immune to stratification, the hybrid approach of ascertaining variants in GWAS but re-estimating effect sizes in siblings reduces but does not eliminate stratification. We show that the effect of population stratification depends not only on allele frequencies and environmental structure but also on demographic history.

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Author details

  1. Arslan A Zaidi

    Genetics, University of Pennsylvania, Philadelphia, United States
    For correspondence
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-2155-8367
  2. Iain Mathieson

    Department of Genetics, University of Pennsylvania, Philadelphia, United States
    For correspondence
    Competing interests
    The authors declare that no competing interests exist.


National Institute of General Medical Sciences (R35GM133708)

  • Iain Mathieson

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. George H Perry, Pennsylvania State University, United States

Publication history

  1. Received: July 29, 2020
  2. Accepted: November 16, 2020
  3. Accepted Manuscript published: November 17, 2020 (version 1)


? 2020, Zaidi & Mathieson

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.


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