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Power and instrument strength requirements for Mendelian randomization studies using multiple genetic variants

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Pierce, Brandon L, Ahsan, Habibul, VanderWeele, Tyler J·2011·International Journal of Epidemiology

Abstract

BACKGROUND: Mendelian Randomization (MR) studies assess the causality of an exposure-disease association using genetic determinants [i.e. instrumental variables (IVs)] of the exposure. Power and IV strength requirements for MR studies using multiple genetic variants have not been explored. METHODS: We simulated cohort data sets consisting of a normally distributed disease trait, a normally distributed exposure, which affects this trait and a biallelic genetic variant that affects the exposure. We estimated power to detect an effect of exposure on disease for varying allele frequencies, effect sizes and samples sizes (using two-stage least squares regression on 10,000 data sets-Stage 1 is a regression of exposure on the variant. Stage 2 is a regression of disease on the fitted exposure). Similar analyses were conducted using multiple genetic variants (5, 10, 20) as independent or combined IVs. We assessed IV strength using the first-stage F statistic. RESULTS: Simulations of realistic scenarios indicate that MR studies will require large (n > 1000), often very large (n > 10,000), sample sizes. In many cases, so-called 'weak IV' problems arise when using multiple variants as independent IVs (even with as few as five), resulting in biased effect estimates. Combining genetic factors into fewer IVs results in modest power decreases, but alleviates weak IV problems. Ideal methods for combining genetic factors depend upon knowledge of the genetic architecture underlying the exposure. CONCLUSIONS: The feasibility of well-powered, unbiased MR studies will depend upon the amount of variance in the exposure that can be explained by known genetic factors and the 'strength' of the IV set derived from these genetic factors.

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Metadata

Authors
Pierce, B. L., Ahsan, H., & VanderWeele, T. J.
Venue
International Journal of Epidemiology
Published
2010-09-15
Volume
40
Issue
3
Pages
740-752
ISSN
  • 0300-5771 (ISSN-L)
  • 1464-3685
OpenAlex
W2112203259
Cited by
1,836
References
13
FWCI
8.55
Type
journal article
Language
en
Open access
green

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CoChat. (2026). Citation check: Power and instrument strength requirements for Mendelian randomization studies using multiple genetic variants. https://app.cochat.ai/papers/10.1093/ije/dyq151
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Pierce, B. L., Ahsan, H., & VanderWeele, T. J. (2011). Power and instrument strength requirements for Mendelian randomization studies using multiple genetic variants. International Journal of Epidemiology. https://doi.org/10.1093/ije/dyq151

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Contains information from the Semantic Scholar Academic Graph Datasets, made available under the ODC Attribution License (ODC-BY 1.0).

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