Cited by 1,648Meta-analysis and systematic reviewsStatistical Methods in EpidemiologyAdvanced Causal Inference Techniques

Strengthening the Reporting of Observational Studies in Epidemiology using Mendelian Randomisation (STROBE-MR): explanation and elaboration.

Open access
Skrivankova, Veronika W, Richmond, Rebecca C, Woolf, Benjamin A R, Davies, Neil M, Swanson, Sonja A, VanderWeele, Tyler J, Timpson, Nicholas J, Higgins, Julian P T +7 more·2021·BMJ

Abstract

Mendelian randomisation (MR) studies allow a better understanding of the causal effects of modifiable exposures on health outcomes, but the published evidence is often hampered by inadequate reporting. Reporting guidelines help authors effectively communicate all critical information about what was done and what was found. STROBE-MR (strengthening the reporting of observational studies in epidemiology using mendelian randomisation) assists authors in reporting their MR research clearly and transparently. Adopting STROBE-MR should help readers, reviewers, and journal editors evaluate the quality of published MR studies. This article explains the 20 items of the STROBE-MR checklist, along with their meaning and rationale, using terms defined in a glossary. Examples of transparent reporting are used for each item to illustrate best practices.

AI snapshot

Written from the paper’s full text.

TL;DR

STROBE-MR is a 20-item reporting checklist for Mendelian randomisation (MR) studies, and this article explains each item and provides examples of transparent reporting. It aims to help authors, reviewers, and journal editors communicate and appraise MR studies more clearly.

Key findings

  • STROBE-MR comprises 20 reporting items covering title/abstract, introduction, methods, results, discussion, and other information; it was developed by an expert group and revised after a July 2019 preprint and debate at the 4th International Mendelian Randomisation Conference.
  • The paper states that empirical evidence indicates many MR reports do not clearly state or examine MR assumptions and report insufficient details on data sources, making quality and reliability difficult to evaluate.
  • This explanation and elaboration document explains the rationale of each checklist item and uses published MR studies as examples of transparent reporting; the examples are not necessarily ideal but highlight the intended issue for each item.
  • The authors encourage MR study authors, reviewers, and journal editors to use STROBE-MR to improve reporting.

Methods

  • Guideline development: the initiative was established in 2018 following guidance for developing medical research reporting guidelines; an expert group met face-to-face in Bristol, UK, over two days in May 2019 to discuss empirical evidence and draft checklist items.
  • The draft checklist was published as a preprint in July 2019, debated on the preprint platform, social media, and at the 4th International Mendelian Randomisation Conference, then revised.
  • This article is an explanation and elaboration document complementing the STROBE-MR statement; it explains the 20 checklist items using a glossary and examples identified from published MR studies, with some examples edited by removing citations and unrelated sections.

Limitations

  • The paper states that STROBE-MR is not intended as a formal tool for assessing methodological or reporting quality and should not be transformed into a quality scale; it is also not a formal guideline to design and conduct MR studies.
  • The paper states that some items will not apply to MR studies that do not use an instrument for the exposure or do not report instrumental variable estimates, though the checklist still provides useful guidance.
  • The paper states that the examples do not necessarily represent the ideal statement for each checklist item; evident from the text, this is a consensus/guideline explanation and elaboration without reported empirical validation of whether STROBE-MR improves reporting quality.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1136/bmj.n2233

Cites

138 of 138 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 101 cited sources checked · 0 supported · 0 flagged

  • Findingcitation

    Many reports of Mendelian randomisation studies do not clearly state or examine the various assumptions of Mendelian randomisation methods.

    “Empirical evidence22 23 24 indicates that many reports of MR studies do not clearly state or examine the various assumptions of MR methods”
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  • Findingcitation

    Many reports of Mendelian randomisation studies report insufficient details on the data sources.

    “and report insufficient details on the data sources”
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  • Findingreasoning

    The quality of reporting of Mendelian randomisation studies has been inconsistent.

    “As a result, the quality of reporting of these studies has been inconsistent.”
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  • Premisecitation

    Associations reported in epidemiological studies can be produced by confounding.

    “and can be produced by confounding (that is, by another factor that affects both the outcome and exposure)1 2 3”
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  • Interpretationreasoning

    Genetic variants are generally not influenced by the outcome and therefore, by reverse causation.

    “Similarly, genetic variants are generally not influenced by the outcome and therefore, by reverse causation.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Genetic variation is essentially randomly inherited from parents to offspring at conception.
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  • The quote only partly states this claim. 1
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    Interpretationreasoning

    These features make genetic variants suitable candidates as instrumental variables, which can help estimate the causal effects of modifiable exposures on outcomes.

    “These features make genetic variants suitable candidates as instrumental variables, which can help estimate the causal effects of modifiable exposures on outcomes.7”
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    • cites [7] source

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    • Rests on an assumption: Genetic variation is essentially randomly inherited from parents to offspring at conception.
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    Premisenone given

    Mendelian randomisation is not limited to studies using genetic variants to generate instrumental variable estimates.

    “MR is not limited to studies using genetic variants to generate instrumental variable estimates (box 1, table 1); however, these studies dominate the literature.”
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    Interpretationnone given

    Mendelian randomisation studies allow a better understanding of the causal effects of modifiable exposures on health outcomes.

    “Mendelian randomisation (MR) studies allow a better understanding of the causal effects of modifiable exposures on health outcomes”
    Quote in the paperNot a substantial claim
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    Premisecitation

    The term "mendelian randomisation" was introduced in 1991 for investigations of bone marrow transplantation in the treatment of childhood malignancies.

    “Indeed, the term “mendelian randomisation” was introduced in 1991 for investigations of bone marrow transplantation in the treatment of childhood malignancies.11 12”
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    • cites [11] Gray, 1991, How to avoid bias when comparing bone marrow transplantation with chemotherapy, Bone Marrow Transplant

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    • cites [12] Davey Smith G. Capitalising on Mendelian randomization to assess the effects of treatments. 2006. https://www.jameslindlibrary.org/articles/capitalising-on-mendelian-randomization-to-assess-the-effects-of-treatments/

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    Interpretationreasoning

    Having an HLA compatible sibling (as a matter of chance) could also serve as a genetic instrument for bone marrow transplantation, and so might be used to infer effects of transplantation on cancer outcomes.

    “Having an HLA compatible sibling (as a matter of chance) could also serve as a genetic instrument for bone marrow transplantation, and so might be used to infer effects of transplantation on cancer outcomes.”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim.

    Interpretationnone given

    STROBE-MR assists authors in reporting their Mendelian randomisation research clearly and transparently.

    “STROBE-MR (strengthening the reporting of observational studies in epidemiology using mendelian randomisation) assists authors in reporting their MR research clearly and transparently.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Reporting guidelines help authors effectively communicate all critical information about what was done and what was found.
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    Premisecitation

    Concerns about violations of the independence assumption usually focus on confounding by ancestry (or population stratification), but it can also be violated by various forms of selection or collider bias, by dynastic effects, or by assortative mating.

    “Concerns about violations of the independence assumption usually focus on confounding by ancestry (or population stratification). However, it can also be violated by various forms of selection or collider bias, by dynastic effects, or by assortative mating.62 63 64”
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    • cites 62 63 64

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    • The authors state this as an assumption: Independence: genetic variant G shares no unmeasured cause with outcome Y.
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    Premisenone given

    Study methods could evolve over time.

    “Also, study methods could evolve over time.”
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    Premisereasoning

    Readers need information on the population(s) studied, setting, and locations to assess the context and generalisability of the study results.

    “Readers need information on the population(s) studied, setting, and locations to assess the context and generalisability of the study results.”
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    Interpretationcitation

    The inclusion of variants in high linkage disequilibrium might not contribute additional information in estimating the causal effect, and could even lead to biased estimates of standard errors if this correlation structure is not accounted for.

    “The inclusion of variants in high linkage disequilibrium might not contribute additional information in estimating the causal effect, and could even lead to biased estimates of standard errors if this correlation structure is not accounted for.47”
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  • Classified as probably not a substantial claim.

    Premisenone given

    The STROBE-MR guidelines are aimed at the currently large majority of Mendelian randomisation studies that are implemented within an instrumental variable framework.

    “The STROBE-MR (strengthening the reporting of observational studies in epidemiology using mendelian randomisation) guidelines are aimed at the (currently) large majority of MR studies that are implemented within an instrumental variable framework.”
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    Premisenone given

    Sources of data could be from meta-analyses of multiple samples.

    “Furthermore, sources of data could be from meta-analyses of multiple samples.”
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    Premisecitation

    MR Egger regression relaxes the exclusion restriction assumption but imposes an InSIDE assumption that the size of the direct effects of the genetic variants on the outcome that do not operate through the exposure are independent of the size of the genetic variants' effects on the exposure.

    “MR Egger regression relaxes the exclusion restriction assumption but imposes an InSIDE assumption that the size of the direct effects of the genetic variants on the outcome that do not operate through the exposure are independent of the size of the genetic variants’ effects on the exposure.”
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    • cites [55] source

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    • The authors state this as an assumption: The size of the direct effects of the genetic variants on the outcome that do not operate through the exposure are independent of the size of the genetic variants’ effects on the exposure (InSIDE).
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    Premisenone given

    Articulating the assumptions also motivates sensitivity analyses and other additional analyses used to assess the assumptions or the robustness of conclusions to their violations.

    “Articulating the assumptions also motivates sensitivity analyses and other additional analyses used to assess the assumptions or the robustness of conclusions to their violations.”
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    Premisecitation

    Power calculations provide information about sample sizes needed to obtain appropriate power for desired precision of the effect estimate.

    “Power calculations provide information about sample sizes needed to obtain appropriate power for desired precision of the effect estimate,43 44”
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    Premisenone given

    Some MR studies draw on multiple sources of data, such as different sources for the ascertainment of the association between the genetic variant and exposure and for the association between the genetic variant and outcome.

    “Some MR studies draw on multiple sources of data (eg, different sources for the ascertainment of the association between the genetic variant and exposure, and for the association between the genetic variant and outcome).”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim.

    Premisecitation

    Instrumental variable estimation to obtain effect estimates imposes a fourth assumption, typically effect homogeneity or monotonicity.

    “When instrumental variable estimation is used to obtain effect estimates, a fourth assumption should then be stated: typically, an assumption of effect homogeneity53 or monotonicity.54”
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    Premisenone given

    The two sample MR approach assumes that the association between the genetic variants and the exposure is the same in the two samples, which might not hold if samples are selected from different subpopulations (eg, by sex, age, ethnicity).

    “Additionally, the two sample MR approach assumes that the association between the genetic variants and the exposure is the same in the two samples, which might not hold if samples are selected from different subpopulations (eg, by sex, age, ethnicity).”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: The association between the genetic variants and the exposure is the same in the two samples (two sample MR).
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    Premisenone given

    In a two sample MR study, one stage can use summary data and another stage can use individual level data.

    “In a two sample MR study, one stage can use summary data and another stage can use individual level data.”
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    Premisecitation

    Presenting critical elements of study design early in the article allows readers to orient themselves on the study basics.

    “As in STROBE,26 presenting critical elements of study design early in the article allows readers to orient themselves on the study basics.”
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    Premisenone given

    The STROBE-MR reporting guidelines are meant to apply to studies that use properties of germline genetic variants to strengthen causal inference regarding possible effects of potentially modifiable exposures on outcomes.

    “The STROBE-MR reporting guidelines are meant to apply to studies that use properties of germline genetic variants to strengthen causal inference regarding possible effects of potentially modifiable exposures on outcomes.”
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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The STROBE guidelines for observational research were developed for the three main study designs in epidemiology: cohort, case-control, and cross sectional studies.

    “The STROBE (strengthening the reporting of observational studies in epidemiology) guidelines for observational research25 26 were developed for the three main study designs in epidemiology (cohort, case-control, and cross sectional studies).”
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    Premisenone given

    MR can be used to test causal null hypotheses or estimate point, period, or lifetime effects.

    “MR can be used to test causal null hypotheses or estimate point, period, or lifetime effects.”
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    Premisecitation

    Estimating effect sizes through the instrumental variable approach imposes a fourth assumption, usually homogeneity of effects of the exposure on the outcome.

    “Estimating effect sizes through the instrumental variable approach imposes a fourth assumption, usually homogeneity of effects of the exposure on the outcome.16 58 59 60”
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    • cites 58 59 60

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    • The authors state this as an assumption: The exposure has the same effects in everyone (homogeneity).
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Premisenone given

    Other aspects, such as temporal stability of association, population specificity, or biological plausability, could help understand the selected genetic variants' validity to be used as instrumental variables.

    “Other aspects, such as temporal stability of association, population specificity, or biological plausability, could help understand the selected genetic variants’ validity to be used as instrumental variables.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Interpretationreasoning

    Some STROBE items are either too general or do not apply to Mendelian randomisation studies, while other items relevant to Mendelian randomisation studies are missing.

    “Some STROBE items are either too general or do not apply to MR studies, while other items relevant to MR studies are missing.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisenone given

    When planning a study or interpreting the analysis results, information about the sample size is essential.

    “When planning a study or interpreting the analysis results, information about the sample size is essential.”
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    Interpretationreasoning

    Statistical power is best ascertained by examination of the 95% confidence intervals of the estimates, since they require fewer assumptions than pre-experiment power calculations.

    “Statistical power is best ascertained by examination of the 95% confidence intervals of the estimates, since they require fewer assumptions than pre-experiment power calculations.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductcitation

    The STROBE-MR initiative was established in 2018, following guidance for the development of medical research reporting guidelines.

    “Described in detail elsewhere,27 we established this initiative in 2018, following guidance for the development of medical research reporting guidelines.28”
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    Premisenone given

    When multiple variants are used in the analysis, these assumptions pertain to each of the variants.

    “When multiple variants are used in the analysis, these assumptions pertain to each of the variants.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Relevance: genetic variant G is associated with the exposure of interest X.
    • The authors state this as an assumption: Independence: genetic variant G shares no unmeasured cause with outcome Y.
    • The authors state this as an assumption: Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.
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    Premisereasoning

    Explicitly stating the three core instrumental variable assumptions, ideally in the methods sections, can help readers to understand the underlying premises of the MR method, and to allow them to judge their validity.

    “Explicitly stating the three core instrumental variable assumptions, ideally in the methods sections, can help readers to understand the underlying premises of the MR method, and to allow them to judge their validity.”
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    Premisenone given

    For two sample MR, this information will often require referring to supplementary material presented in previously published articles.

    “For two sample MR, this information will often require referring to supplementary material presented in previously published articles.”
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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Two sample Mendelian randomisation studies are most commonly conducted with summary level data, where the weights are derived from the first sample and then applied in the second sample to estimate the gene-outcome association.

    “Two sample MR studies are most commonly conducted with summary level data, where the weights are derived from the first sample, which are then applied in the second sample to estimate the gene-outcome association.”
    Quote in the paperNot a substantial claim
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    Premisecitation

    The exclusion restriction is sometimes also referred to as an assumption of no horizontal pleiotropy, but it can be violated in several other ways, including by gene-exposure interaction, by having some form of time varying exposures, by measurement error in the exposure that is related to the instrument, or by a multi-component exposure.

    “The exclusion restriction is sometimes also referred to as an assumption of no horizontal pleiotropy (box 3), but it can be violated in several other ways (eg, by gene-exposure interaction, by having some form of time varying exposures, by measurement error in the exposure that is related to the instrument or by a multi-component exposure).59”
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    • The authors state this as an assumption: Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.
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    Premisenone given

    The F statistic can also be approximated using summary level data.

    “The F statistic can also be approximated using summary level data.”
    Quote in the paperNot a substantial claim
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    Interpretationreasoning

    Other study designs, such as twin studies, also use the basic principles of mendelian genetics and so can be considered a form of Mendelian randomisation.

    “Other study designs, such as twin studies, also use the basic principles of mendelian genetics and so can be considered a form of MR.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Premisereasoning

    The independence assumption cannot be directly verified, but it can be partially assessed in many research settings.

    “The independence assumption cannot be directly verified, but it can be partially assessed in many research settings.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Independence: genetic variant G shares no unmeasured cause with outcome Y.
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisereasoning

    Providing a description of the ancestry of the participants will help understand potential sources of heterogeneity and generalisability of results.

    “Providing a description of the ancestry of the participants will help understand potential sources of heterogeneity and generalisability of results.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Premisenone given

    Exposures such as environmental factors and therapies can change over time.

    “Exposures such as environmental factors and therapies can change over time.”
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  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisenone given

    Detailed descriptions of the study participants and sampling frame help readers understand the applicability of the results.

    “Detailed descriptions of the study participants and sampling frame help readers understand the applicability of the results.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Reporting the F statistic, if individual level data are available, provides several advantages for understanding the risk of weak instrument bias.

    “Reporting the F statistic, if individual level data are available, provides several advantages for understanding the risk of weak instrument bias.65”
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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The homogeneity assumption can also be replaced by imposing a monotonicity assumption that an increase in the number of risk alleles does not lower the likelihood of exposure for any individuals, typically leading to estimating an effect in a subgroup of the study population.

    “The homogeneity assumption can also be replaced by imposing a monotonicity assumption that an increase in the number of risk alleles does not lower the likelihood of exposure for any individuals, typically leading to estimating an effect in a subgroup of the study population.61”
    Quote in the paperNot a substantial claim0 of 1 sources checked
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    • The authors state this as an assumption: An increase in the number of risk alleles does not lower the likelihood of exposure for any individuals (monotonicity).
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisecitation

    Reporting associations between measured covariates that might confound the variant-outcome association can also prove helpful, particularly if scaled by instrument strength or presented alongside a related bias analytical approach.

    “Reporting associations between measured covariates that might confound the variant-outcome association can also prove helpful, particularly if scaled by instrument strength67 68 or presented alongside a related bias analytical approach.69”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites 67 68

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    • The authors state this as an assumption: Independence: genetic variant G shares no unmeasured cause with outcome Y.
  • Classified as probably not a substantial claim.

    Premisenone given

    Mendelian randomisation only provides estimates intended to inform understanding of causal associations under specific assumptions.

    “The word “causal” should be used carefully, because MR only provides estimates intended to inform our understanding of causal associations under specific assumptions.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    In case-control studies, the choice of cases and controls is crucial to interpreting the results, and the method of their selection has major implications for study validity.

    “In case-control studies, the choice of cases and controls is crucial to interpreting the results, and the method of their selection has major implications for study validity.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisereasoning

    Providing information on the ascertainment of genotypes and their quality control will enable readers to assess the quality of the genetic variants used in the study.

    “Providing information on the ascertainment of genotypes and their quality control will enable readers to assess the quality of the genetic variants used in the study.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisereasoning

    Knowing when a study took place and over what period participants were recruited and followed up puts the study in historical context, which is essential for interpreting results.

    “Knowing when a study took place and over what period participants were recruited and followed up puts the study in historical context, which is essential for interpreting results.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). The quote only partly states this claim.

    Premisereasoning

    When homogeneity and monotonicity assumptions do not hold, the estimation is replaced by testing for a non-null effect.

    “Instead, the estimation is replaced by testing for a non-null effect.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Interpretationnone given

    Although the heterogeneity test is often interpreted as an assessment of the exclusion restriction, it is jointly testing the exclusion restriction, independence, and homogeneity assumptions.

    “Although this test is often interpreted as an assessment of the exclusion restriction, it is jointly testing the exclusion restriction, independence, and homogeneity assumptions.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: Relevance: genetic variant G is associated with the exposure of interest X.
    • The authors state this as an assumption: Independence: genetic variant G shares no unmeasured cause with outcome Y.
    • The authors state this as an assumption: Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.
    • The authors state this as an assumption: The exposure has the same effects in everyone (homogeneity).
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Evidence on the consistency of the genetic variant's association with the exposure or outcome helps to understand the degree of heterogeneity of effects.

    “Evidence on the consistency of the genetic variant’s association with the exposure or outcome helps to understand the degree of heterogeneity of effects.”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim. May combine two claims.

    Premisenone given

    Many assumptions underlying Mendelian randomisation cannot be verified, but there are methods available to attempt to falsify them.

    “While many assumptions cannot be verified, there are methods available to attempt to falsify them.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationnone given

    If the homogeneity and monotonicity assumptions do not hold, it might be preferable not to report the estimates and outline this situation.

    “However, if the homogeneity and monotonicity assumptions do not hold, it might be preferable not to report the estimates and outline this situation.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisereasoning

    Readers can assess group differences better if the descriptive statistics are provided for each category separately.

    “Readers can assess group differences better if the descriptive statistics are provided for each category separately.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing). May combine two claims.

    Premisenone given

    Distributions of continuous variables are easily summarised by mean and standard deviation, or by median and percentile range in case of asymmetrical distribution.

    “Distributions of continuous variables are easily summarised by mean and standard deviation, or by median and percentile range (eg, 25th and 75th percentiles) in case of asymmetrical distribution.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisenone given

    Information on study participants helps readers understand the target population and assess the validity and generalisability of results.

    “Information on study participants will help readers understand the target population and assess the validity and generalisability of results.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisereasoning

    A global exploration of the homogeneity assumption can examine any differences in variance of a continuous outcome across the genetic instrument; the extent of such differences provides evidence as to extent of violation of the homogeneity assumption.

    “Furthermore, a global exploration of the homogeneity assumption can examine any differences in variance of a continuous outcome across the genetic instrument; the extent of such differences provides evidence as to extent of violation of the homogeneity assumption.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: The exposure has the same effects in everyone (homogeneity).
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisenone given

    Reporting on the association between the genetic variant and the outcome is useful because it can provide an initial indication about the possibility of a causal association between the exposure and outcome.

    “Reporting on the association between the genetic variant and the outcome is useful because it can provide an initial indication about the possibility of a causal association between the exposure and outcome.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationnone given

    If the results from all the approaches are largely consistent, authors can have more confidence in drawing robust conclusions regarding the presence and magnitude of a causal effect.

    “If the results from all the approaches are largely consistent, author can have more confidence in drawing robust conclusions regarding the presence and magnitude of a causal effect.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Independent replication of MR findings in an independent dataset or with a different study design (eg, one sample v two sample MR) is typically advocated to assess the findings' robustness.

    “Independent replication of MR findings in an independent dataset or with a different study design (eg, one sample v two sample MR) is typically advocated to assess the findings’ robustness.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Relevance: genetic variant G is associated with the exposure of interest X.
    • The authors state this as an assumption: Independence: genetic variant G shares no unmeasured cause with outcome Y.
    • The authors state this as an assumption: Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.
    • The authors state this as an assumption: The exposure has the same effects in everyone (homogeneity).
  • Classified as probably not a substantial claim.

    Premisereasoning

    Reporting the association between the genetic variant and the exposure is required to evaluate the relevance assumption.

    “Reporting the association between the genetic variant and the exposure is required to evaluate the relevance assumption (item 8b).”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    The use of known biological effects of a SNP can also be leveraged to decrease the probability of violation of the exclusion restriction assumption.

    “The use of known biological effects of a SNP can also be leveraged to decrease the probability of violation of this assumption.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The E value can be used to understand the degree to which unmeasured confounding might explain findings.

    “The E value69 can be used to understand the degree to which unmeasured confounding might explain findings.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [69] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    The first three core assumptions pertain to any MR analysis with a single instrument; the additional assumptions are needed for instrumental variable estimation.

    “The first three core assumptions pertain to any MR analysis with a single instrument; the additional assumptions are needed for instrumental variable estimation.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Comparing levels of exposure across the genotype distribution can indicate monotonicity and linearity of the genetic effect.

    “Comparing levels of exposure across the genotype distribution can also indicate monotonicity and linearity of the genetic effect.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisenone given

    Information on the distribution of the exposure, outcomes, and other variables helps judge the comparability of groups and generalisability of the findings.

    “Information on the distribution of the exposure, outcomes, and other variables helps judge the comparability of groups and generalisability of the findings.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    An allele score could be weighted or unweighted.

    “An allele score could be weighted or unweighted.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Each study design has different types of biases and could have different degrees of statistical power.

    “Each study design has different types of biases and could have different degrees of statistical power.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisecitation

    Simulations might also help understand the plausible size and direction of bias induced by assortative mating, dynastic effects, and time varying effects, if deemed relevant.

    “Simulations might also help understand the plausible size and direction of bias induced by assortative mating,62 dynastic effects,9 63 and time varying effects,77 if deemed relevant.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [62] source

      Not checked in the free run.

    • cites 9 63

      Not checked in the free run.

    • cites [77] source

      Not checked in the free run.

    • The authors state this as an assumption: Relevance: genetic variant G is associated with the exposure of interest X.
    • The authors state this as an assumption: Independence: genetic variant G shares no unmeasured cause with outcome Y.
    • The authors state this as an assumption: Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.
    • The authors state this as an assumption: The exposure has the same effects in everyone (homogeneity).
  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationnone given

    If the instrumental variable assumptions are not apparently falsified and are generally supported, or sensitivity analyses are robust to violation of the assumptions, then estimates from the MR analysis can be reported in a meaningful manner.

    “If the instrumental variable assumptions are not apparently falsified and are generally supported, or sensitivity analyses are robust to violation of the assumptions (item 8b), then estimates from the MR analysis can be reported in a meaningful manner, preferably on an intuitive scale (eg, relative risk, risk difference).”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Exclusion restriction is relaxed in sensitivity analyses such as MR Egger regression.

    “Exclusion restriction is relaxed in sensitivity analyses such as MR Egger regression.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based).

    Interpretationnone given

    Wider adoption of pre-registration methods should increase the accuracy, transparency, and robustness of MR studies.

    “Wider adoption of these methods should increase the accuracy, transparency, and robustness of MR studies.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Premisecitation

    MR Egger regression can be used to detect certain versions of pleiotropy and therefore provide evidence of certain violations of the exclusion restriction.

    “For the exclusion restriction assumption, MR Egger regression55 can be used to detect certain versions of pleiotropy and therefore provide evidence of certain violations of the exclusion restriction.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [55] source

      Not checked in the free run.

    • The authors state this as an assumption: Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationreasoning

    Putting the MR results in context will help readers understand if the strengths and weaknesses of MR allow for results that support or contradict previous evidence.

    “Putting the MR results in context will help readers understand if the strengths and weaknesses of MR allow for results that support or contradict previous evidence.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing). May combine two claims.

    Premisereasoning

    Information on study participants provides readers with the information needed to replicate the study and to assess whether the study is likely to show collider bias.

    “It also provides readers with the information needed to replicate the study and to assess whether the study is likely to show collider bias.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Any transformations made in the quantitative variables (that is, exposure, outcome, or relevant covariates) affect both interpretation of results and their comparability with other studies.

    “Any transformations made in the quantitative variables (that is, exposure, outcome, or relevant covariates) should be explicitly mentioned, because they affect both interpretation of results and their comparability with other studies.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Plots can be useful for examining potential violations of the instrumental variable assumptions, especially for the exclusion restriction assumption.

    “Plots can be useful for examining potential violations of the instrumental variable assumptions, especially for the exclusion restriction assumption.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisenone given

    Numbers and percentages best describe categorical variables.

    “Numbers and percentages best describe categorical variables.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    Two-sample MR analyses assume that the SNP-exposure associations are similar in the two samples.

    “Two sample MR analyses assume that the SNP-exposure associations are similar in the two samples.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    The homogeneity assumption requires that the exposure has the same effects in everyone, which is not directly verifiable.

    “The homogeneity assumption requires that the exposure has the same effects in everyone, which is not directly verifiable.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: The exposure has the same effects in everyone (homogeneity).
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationreasoning

    A measure of absolute risk can provide an estimate of the excess amount of disease that can be attributed to the exposure over a particular period, which can then be used to estimate the absolute benefit of an intervention aimed at reducing levels of the exposure.

    “A measure of absolute risk can provide an estimate of the excess amount of disease that can be attributed to the exposure over a particular period, which can then be used to estimate the absolute benefit of an intervention aimed at reducing levels of the exposure.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    If the estimation is based on a meta-analysis, the number of included studies helps determine if tests for heterogeneity are properly powered to detect its presence.

    “If the estimation is based on a meta-analysis, the number of included studies will also help determine if tests for heterogeneity are properly powered to detect its presence.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Premisenone given

    Associations with measured covariates and effect estimates across subpopulations can be reported with one-sample MR studies, but generally not with two-sample MR studies.

    “Associations with measured covariates (eg, age, sex, and race or ethnic origin) and effect estimates across subpopulations can be reported with one sample MR studies, but generally not with two sample MR studies”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    The inclusion of multiple variants with missing data in the estimation of causal effects could decrease precision.

    “The inclusion of multiple variants with missing data in the estimation of causal effects could decrease precision.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    When selection bias is a concern, researchers also frequently conduct simulations to understand the plausible size and direction of bias.

    “When selection bias is a concern, researchers also frequently conduct simulations to understand the plausible size and direction of bias.64”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [64] source

      Not checked in the free run.

    • The authors state this as an assumption: Relevance: genetic variant G is associated with the exposure of interest X.
    • The authors state this as an assumption: Independence: genetic variant G shares no unmeasured cause with outcome Y.
    • The authors state this as an assumption: Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.
    • The authors state this as an assumption: The exposure has the same effects in everyone (homogeneity).
  • Classified as probably not a substantial claim.

    Premisecitation

    Because several of the estimators using multiple genetic variants rely on different versions of relaxing or adapting the instrumental variable assumptions, a comparison of estimates obtained using each of these approaches can help understand the sensitivity of effect estimates to the non-overlapping assumptions of each.

    “Because several of the estimators using multiple genetic variants rely on different versions of relaxing or adapting the instrumental variable assumptions (eg, MR Egger, median based, or modal based estimators), a comparison of estimates obtained using each of these approaches can help understand the sensitivity of effect estimates to the non-overlapping assumptions of each.74”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [74]

      Not checked in the free run.

    • The authors state this as an assumption: Relevance: genetic variant G is associated with the exposure of interest X.
    • The authors state this as an assumption: Independence: genetic variant G shares no unmeasured cause with outcome Y.
    • The authors state this as an assumption: Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.
    • The authors state this as an assumption: The exposure has the same effects in everyone (homogeneity).
  • Classified as probably not a substantial claim.

    Interpretationnone given

    In two-sample Mendelian randomisation, differences in the use of covariates between the genetic variant-exposure and genetic variant-outcome associations could lead to bias.

    “For a two sample analysis, authors should state the covariates used to estimate the genetic variant-exposure and genetic variant-outcome associations to assess any differences in the use of covariates between the two associations, which could lead to bias.”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationnone given

    Sensitivity analyses can test the robustness of effect estimates to plausible violations of the underlying assumptions and help understand the plausible size or direction of bias.

    “Sensitivity analyses can test the robustness of effect estimates to plausible violations of the underlying assumptions and help understand the plausible size or direction of bias.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationreasoning

    In some instances, the interpretation of estimates in terms of absolute risks or risk differences rather than relative risk differences might be more clinically meaningful, by taking into account the baseline risk.

    “In some instances, the interpretation of estimates in terms of absolute risks or risk differences rather than relative risk differences might be more clinically meaningful, by taking into account the baseline risk.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    One possibility for supporting the validity of the homogeneity assumption is to determine whether the effect estimate, or even the genetic variants' effects on the exposure, is the same across subpopulations.

    “One possibility for supporting its validity is to determine whether the effect estimate, or even the genetic variants’ effects on the exposure, is the same across subpopulations.67 71”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites 67 71

      Not checked in the free run.

    • The authors state this as an assumption: The exposure has the same effects in everyone (homogeneity).
  • May combine two claims.

    Premisenone given

    The MR Egger approach depends on an additional assumption and requires multiple independent variants.

    “However, the approach depends on an additional assumption (described above) and requires multiple independent variants.”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisereasoning

    A summary measure of follow-up time is important to understand the period over which events were recorded.

    “A summary measure of follow-up time—such as mean, median, or total follow-up—is also important to understand the period over which events were recorded.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Interpretationcitation

    The winner's curse bias is a linear function of the number of individuals included in both samples, so the consequences of a small amount of overlap may not be severe.

    “The bias is a linear function of the number of individuals included in both samples, so the consequences of a small amount of overlap may not be severe.94”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [94] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing). May combine two claims.

    Premisecitation

    Additional plots might also aid in the visualisation of results, assessing assumption violation, and detecting potential influential or outlier points.

    “Additional plots might also aid in the visualisation of results, assessing assumption violation, and detecting potential influential or outlier points.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [84] source

      Not checked in the free run.

    • cites [105] source

      Not checked in the free run.

    • cites [32] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Premisecitation

    In general, causal inference can be presented in a triangulation framework, evaluating the overall body of evidence from several different approaches.

    “In general, causal inference can be presented in a triangulation framework, evaluating the overall body of evidence from several different approaches.103 104”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [103] source

      Not checked in the free run.

    • cites [104] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    Usually MR studies are interpreted as a so-called lifetime effect of the exposure, but some settings (eg, MR studies in pregnant women to study prenatal exposures) lend themselves to studies of period effects.

    “Usually MR studies are interpreted as a so-called lifetime effect of the exposure, but some settings (eg, MR studies in pregnant women to study prenatal exposures) lend themselves to studies of period effects.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable).

    Premisereasoning

    Because many interventions cannot be tested in randomised clinical trials, MR evidence might help to better understand the possible causal effect of the exposure on the outcome.

    “Because many interventions cannot be tested in randomised clinical trials, MR evidence might help to better understand the possible causal effect of the exposure on the outcome (box 4).”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Premisecitation

    The long term effect of lowered low density lipoprotein (LDL) cholesterol can be estimated from early life onwards by MR and is double the effect estimate derived from randomised trials.

    “Conversely, the long term effect of lowered low density lipoprotein (LDL) cholesterol can be estimated from early life onwards by MR and is double the effect estimate derived from randomised trials.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [112] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing). May combine two claims.

    Premisecitation

    Structured discussions can help authors avoid over-interpreting results, and act as a guide for readers.

    “Structured discussions can help authors avoid over-interpreting results, and act as a guide for readers.107 108”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [107] source

      Not checked in the free run.

    • cites [108] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Findings from a cohort of a specific age group collected in the past might not apply to people currently in the same age group.

    “For example, findings from a cohort of a specific age group collected in the past might not apply to people currently in the same age group.118”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [118] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    Time dependency of the effects of instruments is an important issue that should be considered when interpreting MR findings, and is well served by viewing this in the context of gene-environment equivalence.

    “Time dependency of the effects of instruments is an important issue that should be considered when interpreting MR findings, and is well served by viewing this in the context of gene-environment equivalence.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Biobanks or other repositories or databases used in their study have commercial interests that might influence research integrity.

    “Authors should disclose funding sources for biobanks or other repositories or databases used in their study because these entities also have commercial interests that might influence research integrity.124 125”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [124] source

      Not checked in the free run.

    • cites [125] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    This bias is of special concern when research is funded by an entity that has an interest in outcomes that are favourable to its own commercial, academic, or other interests.

    “This bias is of special concern when research is funded by an entity that has an interest in outcomes that are favourable to its own commercial, academic, or other interests.123”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [123] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning

    Describing the source of funding allows readers to evaluate the work's credibility and trustworthiness in the light of any potential influence from funders.

    “Describing the source of funding allows readers to evaluate the work’s credibility and trustworthiness in the light of any potential influence from funders.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Interpretationreasoning

    This difference probably reflects MR providing an estimate of lifelong effects, whereas trials provide an effect estimate for period of randomisation, which lasts just a few years in cholesterol lowering randomised clinical trials.

    “This difference probably reflects MR providing an estimate of lifelong effects, whereas trials provide an effect estimate for period of randomisation, which lasts just a few years in cholesterol lowering randomised clinical trials.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The biological mechanisms that allow genetic variants to be used as instrumental variables are often unknown.

    “While the biological mechanisms that allow genetic variants to be used as instrumental variables are often unknown, the discussion should consider possibilities.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    Many of the instrumental variable assumptions are not empirically verifiable.

    “Authors should address the plausibility of all the instrumental variable assumptions, which is especially important because many of the assumptions are not empirically verifiable.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    An instrumental variable estimate's precision from a meta-analysis of multiple SNPs will usually be greater than that for a single SNP.

    “For example, an instrumental variable estimate’s precision from a meta-analysis of multiple SNPs will usually be greater than that for a single SNP.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationcitation

    Caution is especially warranted when interpreting effect estimates with a binary exposure.

    “Caution is especially warranted when interpreting effect estimates with a binary exposure.114”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [114] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    Genetic variants might not have a constant effect over the entire life course.

    “For example, because genetic variants might not have a constant effect over the entire life course, authors should consider whether the effect estimate derived in the study would generalise to other exposure periods.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    Other sources of influence can include employers, political appointees, and government researchers.

    “Other sources of influence can include employers, political appointees, and government researchers.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    (Residual) genotype-phenotype confounders (such as population structure, genetic nurture, or assortative mating) could lead to a violation of the independence assumption.

    “Authors could consider, for example, the possibility that (residual) genotype-phenotype confounders (such as population structure, genetic nurture, or assortative mating) could lead to a violation of the independence assumption.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The source of research funding can lead to bias or perceptions of bias in the design, conduct, or interpretation of research.

    “The source of research funding can lead to bias or perceptions of bias in the design, conduct, or interpretation of research.121 122”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [121] source

      Not checked in the free run.

    • cites [122] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    MR estimates are directly calculated only for the exposure range caused by differences in alleles. Applying MR results, therefore, might not generalise to a wider exposure range.

    “Also, MR estimates are directly calculated only for the exposure range caused by differences in alleles. Applying MR results, therefore, might not generalise to a wider exposure range.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    Clinical and policy interventions might have different effect sizes compared with the genetic variants included in the MR study.

    “Since clinical and policy interventions might have different effect sizes compared with the genetic variants included in the MR study, extrapolation of this evidence should be clearly described and cautious.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    When financial or ideological interests are not disclosed, public trust in the research enterprise is eroded.

    “When such interests are not disclosed, public trust in the research enterprise is eroded.128”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [128] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    An important component of interpretation is defining the time period.

    “Finally, an important component of interpretation is defining the time period.60”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [60] source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Various components of growth and development could be influenced by the variants, whilst their identification through genetic association studies is often from association with phenotype measured at one time point.

    “Various components of growth and development could be influenced by the variants, whilst their identification through genetic association studies is often from association with phenotype measured at one time point.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Consensus is building that data sharing is an inseparable part of the research process.

    “Consensus is building that data sharing is “an inseparable part of the research process.”127”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [127] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Financial connections between researchers and commercial or other entities and firmly held ideological or intellectual views can lead to bias in the design, conduct, or reporting of study results.

    “Financial connections between researchers and commercial or other entities and firmly held ideological or intellectual views can lead to bias in the design, conduct, or reporting of study results.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [128] source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Effects of genetic variants can influence outcomes from conception onwards and in a manner that can be variable and complex.

    “Effects of genetic variants can influence outcomes from conception onwards and in a manner that can be variable and complex.”
    Quote in the paperSubstantial claim
120 of 120
  • The paper relies on this without support.

    Reporting guidelines help authors effectively communicate all critical information about what was done and what was found.

    “Reporting guidelines help authors effectively communicate all critical information about what was done and what was found.”
  • The paper relies on this without support.

    Genetic variation is essentially randomly inherited from parents to offspring at conception.

    “Genetic variation is essentially randomly inherited from parents to offspring at conception”
  • The paper relies on this without support.

    Mendelian randomisation studies have increased in popularity and have begun to inform understanding of disease causation.

    “Given these advantages, MR studies have increased in popularity and have begun to inform understanding of disease causation.”
  • The authors state this as an assumption.

    Relevance: genetic variant G is associated with the exposure of interest X.

    “I. Relevance: genetic variant G is associated with the exposure of interest X”
  • The authors state this as an assumption.

    Independence: genetic variant G shares no unmeasured cause with outcome Y.

    “II. Independence: genetic variant G shares no unmeasured cause with outcome Y”
  • The authors state this as an assumption.

    Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.

    “III. Exclusion restriction: genetic variant G does not affect outcome Y except through its potential effect on the exposure of interest X.”
  • The authors state this as an assumption.

    The exposure has the same effects in everyone (homogeneity).

    “The homogeneity assumption requires that the exposure has the same effects in everyone, which is not directly verifiable.”
  • The authors state this as an assumption.

    An increase in the number of risk alleles does not lower the likelihood of exposure for any individuals (monotonicity).

    “The homogeneity assumption can also be replaced by imposing a monotonicity assumption that an increase in the number of risk alleles does not lower the likelihood of exposure for any individuals, typically leading to estimating an effect in a subgroup of the study population.61”
  • The authors state this as an assumption.

    The size of the direct effects of the genetic variants on the outcome that do not operate through the exposure are independent of the size of the genetic variants’ effects on the exposure (InSIDE).

    “MR Egger regression relaxes the exclusion restriction assumption but imposes an InSIDE assumption that the size of the direct effects of the genetic variants on the outcome that do not operate through the exposure are independent of the size of the genetic variants’ effects on the exposure.”
  • The authors state this as an assumption.

    The association between the genetic variants and the exposure is the same in the two samples (two sample MR).

    “Additionally, the two sample MR approach assumes that the association between the genetic variants and the exposure is the same in the two samples, which might not hold if samples are selected from different subpopulations (eg, by sex, age, ethnicity).”
  • The paper relies on this without support.

    Original data are needed by readers or researchers who wish to evaluate or replicate analyses.

    “Original data are needed by readers or researchers who wish to evaluate or replicate analyses.”
  • The paper relies on this without support.

    Many funders and journals encourage or require data sharing, and provide guidance to authors about the content of any explicit data sharing statement required by their journal.

    “Many funders and journals encourage or require data sharing, and provide guidance to authors about the content of any explicit data sharing statement required by their journal.”
12 of 12

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Replicated odds ratio for rs4233949 falls outside its confidence interval

    Minor

    The replication-stage odds ratio is 1.04, but its stated 95% confidence interval runs from 1.05 to 1.05.

  • Confidence interval for the BMI allele score association changes between examples

    Minor

    The two examples report the same −0.06% association with 25(OH)D concentrations and P=0.004, but give different lower confidence limits: −0.20% and −0.10%.

  • Replicated odds ratio for rs7851693 falls outside its confidence interval

    Minor

    The replication-stage odds ratio is 1.05, but its stated 95% confidence interval runs from 1.06 to 1.06.

  • One SNP has more fracture cases than the stated combined total

    Minor

    Table 8 lists 185 085 combined fracture cases for rs1286083, exceeding the table note's combined total of 185 057 cases by 28.

4 of 4

Cites

Flagged first, then by citations

Research works printed but not linked: 1

  1. Conference MR. 2019. MRC Integrative Epidemiology Unit. University of Bristol. 2020. https://www.bristol.ac.uk/integrative-epidemiology/seminars/2019/mr-conference-2019.html

Cited by

Sorted by citations

Authors
Skrivankova, V. W., Richmond, R. C., Woolf, B. A. R., Davies, N. M., Swanson, S. A., VanderWeele, T. J., Timpson, N. J., Higgins, J. P. T., Dimou, N., Langenberg, C., Loder, E. W., Golub, R. M., Egger, M., Davey Smith, G., & Richards, J. B.
Affiliations
  • University of Bern (CH)
  • University of Bristol (GB)
  • Norwegian University of Science and Technology (NO)
  • Erasmus MC (NL)
  • Harvard University (US)
  • Centre international de recherche sur le cancer (FR)
  • University of Cambridge (GB)
  • Northwestern University (US)
  • University of London (GB)
Corresponding author
Richards, J Brent
Venue
BMJ
Publisher
BMJ
Published
2021-10-26
Volume
375
Pages
n2233
ISSN
1756-1833 (ISSN-L)
OpenAlex
W3210406414
Cited by
1,648
References
137
Citations by year
2026: 217 · 2025: 484 · 2024: 599 · 2023: 252 · 2022: 91 · 2021: 4
FWCI
140.35
Type
journal article
Language
en
Open access
Locations
  • BMJ (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, other-oa)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • EUR Research Repository (Erasmus University Rotterdam) (publishedVersion, cc-by)
  • EUR Research Repository (Erasmus University Rotterdam) (submittedVersion, cc-by)
  • BORIS (University Library Bern) (submittedVersion, cc-by)
  • Apollo (University of Cambridge) (submittedVersion, cc-by)
  • Apollo
  • Apollo (cc-by)
Funders
  • National Science Foundation (189498)
  • World Health Organization
  • Wellcome Trust (WT 217065/Z/19/Z, 217065/Z/19/Z, 202802/Z/16/Z, 217065, 202802)
  • Public Health Agency of Canada
  • University Hospitals Bristol NHS Foundation Trust
  • Compute Canada
  • NIHR Bristol Biomedical Research Centre (MC_UU_00011/1, BRC‐1215‐2001, NF-SI-0617-10145)
  • Cancer Research UK (C18281/, 29019, C18281 / A19169, 10710, MC_UU_00011/1, 10118, 16563, A19169, 19169)
  • National Institute for Health and Care Research (BRC-1215-2001, C18281/A19169, 217065/Z/19/Z, NF-SI-0617-10145, MC_UU_00011/1)
  • Department of Health and Social Care
  • King's College London
  • European Commission (633784)
  • University of Bristol (C18281/A19169, 217065/Z/19/Z, MC_UU_00011/1)
  • Public Health Agency
  • Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (189498, 10145)
  • ZonMw (91617066)
  • Nederlandse Organisatie voor Wetenschappelijk Onderzoek (91617066)
  • Jewish General Hospital
  • Norges Forskningsråd (189498, 295989)
  • National Institutes of Health (217065/Z/19/Z)
  • Canadian Institutes of Health Research (365825; 409511, 40951_1, 365825)
  • Medical Research Council (MC_UU_00011/6, 217065/Z/19/Z, MR/M005070/1, 202802/Z/16/Z, 217065, WT 217065/Z/19/Z, MC_UU_00011/7, MC_UU_00011/5, MC_UU_00011/1, MC_UU_00011, MC_UU_00011/2)
  • Economic and Social Research Council (+3 PhD Studentship Award, ES/P000630/1, 1+3 PhD Studentship, ES/N000498/1)
  • National Cancer Institute (R01CA222147)
Topics
  • Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
  • Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
  • Physical Sciences › Mathematics › Statistics and Probability › Advanced Causal Inference Techniques
Keywords
reporting guidelines, Mendelian randomization, observational studies, causal inference, reporting checklist, transparency in research reporting, study quality assessment
MeSH terms
Humans, Epidemiologic Research Design, Guidelines as Topic, Mendelian Randomization Analysis, Observational Studies as Topic

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-10.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-10.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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