Cited by 90Genetic Associations and EpidemiologyAdvanced Causal Inference TechniquesStatistical Methods in Epidemiology

Detecting and correcting for bias in Mendelian randomization analyses using Gene-by-Environment interactions.

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Spiller, Wes, Slichter, David, Bowden, Jack, Davey Smith, George·2018·International Journal of Epidemiology

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Abstract

Background: Mendelian randomization has developed into an established method for strengthening causal inference and estimating causal effects, largely due to the proliferation of genome-wide association studies. However, genetic instruments remain controversial as pleiotropic effects can introduce bias into causal estimates. Recent work has highlighted the potential of gene-environment interactions in detecting and correcting for pleiotropic bias in Mendelian randomization analyses. Methods: We introduce MR using Gene-by-Environment interactions (MRGxE) as a framework capable of identifying and correcting for pleiotropic bias, drawing upon developments in econometrics and epidemiology. If an instrument-covariate interaction induces variation in the association between a genetic instrument and exposure, it is possible to identify and correct for pleiotropic effects. The interpretation of MRGxE is similar to conventional summary Mendelian randomization approaches, with a particular advantage of MRGxE being the ability to assess the validity of an individual instrument. Results: We investigate the effect of BMI upon systolic blood pressure (SBP) using data from the UK Biobank and the GIANT consortium using a single instrument (a weighted allelic score). We find MRGxE produces findings in agreement with MR Egger regression in a two-sample summary MR setting, however, association estimates obtained across all methods differ considerably when excluding related participants or individuals of non-European ancestry. This could be a consequence of selection bias, though there is also potential for introducing bias by using a mixed ancestry population. Further, we assess the performance of MRGxE with respect to identifying and correcting for horizontal pleiotropy in a simulation setting, highlighting the utility of the approach even when the MRGxE assumptions are violated. Conclusions: By utilising instrument-covariate interactions within a linear regression framework, it is possible to identify and correct for pleiotropic bias, provided the average magnitude of pleiotropy is constant across interaction covariate subgroups.

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  • The InSIDE assumption would be violated in the case of correlated pleiotropy, which occurs when genetic variants influence a confounder of the exposure and outcome.

    “This assumption would be violated in the case of “correlated pleiotropy”, which occurs when genetic variants influence a confounder of the exposure and outcome (and hence there are correlated pleiotropic effects on the exposure and outcome) 88 .”

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  1. [34]Mackenbach JP. Health and deprivation—inequality and the North In: Townsend P, Phillimore P, Beattie A (eds). Health Policy, Vol. 10. London: Routledge, 1988, p. 207.

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Authors
Spiller, W., Slichter, D., Bowden, J., & Davey Smith, G.
Affiliations
  • University of Bristol (GB)
  • Binghamton University (US)
  • Population Health Sciences, University of Bristol, Bristol, UK
Corresponding author
Spiller, Wes
Venue
International Journal of Epidemiology
Published
2018-11-20
Volume
48
Issue
3
Pages
702-712
ISSN
  • 0300-5771 (ISSN-L)
  • 1464-3685
OpenAlex
W2952562325
Cited by
90
References
54
Citations by year
2026: 2 · 2025: 14 · 2024: 19 · 2023: 5 · 2022: 10 · 2021: 9 · 2020: 17 · 2019: 10 · 2018: 3 · 2017: 1
FWCI
5.98
Type
journal article
Language
en
Open access
Locations
  • International Journal of Epidemiology (publishedVersion, cc-by)
  • bioRxiv (Cold Spring Harbor Laboratory) (acceptedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Explore Bristol Research (submittedVersion, cc-by)
  • Bristol Research (University of Bristol) (submittedVersion, cc-by)
Funders
  • Medical Research Council
  • University of Bristol
  • MRC Integrative Epidemiology Unit (MC_UU_00011/1, MC_UU_00011/2)
  • Wellcome Trust (108902/B/15/Z)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetic Associations and Epidemiology
  • Physical Sciences › Mathematics › Statistics and Probability › Advanced Causal Inference Techniques
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
Keywords
Mendelian randomization, gene-environment interaction, pleiotropy, assessment validity, body mass index, adiposity, systolic blood pressure, causal inference, genetic instruments
MeSH terms
Blood Pressure, Computer Simulation, Humans, Obesity, Bias, Body Mass Index, Biological Specimen Banks, Adiposity, Mendelian Randomization Analysis, Genetic Pleiotropy, Gene-Environment Interaction

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