Evidence map›Paper›PMID 30896457›Full record

ArticleEpidemiology (Cambridge, Mass.)2019

Selection Bias When Estimating Average Treatment Effects Using One-sample Instrumental Variable Analysis.

Rachael A Hughes, Neil M Davies, George Davey Smith, Kate Tilling

Abstract read
In one paragraph

Article in Epidemiology (Cambridge, Mass.), 2019. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 50 papers, 1 of them a synthesis that pooled it.

0numbers the graph read from it
0cells of the map it votes in
50citing papers in PubMed, 1 pooled it
–field-weighted citation impact
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

50 citing papers in PubMed, 1 synthesis or guideline pooled it.

  1. Pooled it
  2. Article
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  6. Article
  7. Article
  8. Article
  9. Mendelian Randomization Analysis of the Causal Effect of Cigarette Smoking on Hospital Costs.Nicotine & tobacco research : official journal of the Society for Research on Nicotine and Tobacco · 2024
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  11. Review
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  13. Causal Estimation of Long-term Intervention Cost-effectiveness Using Genetic Instrumental Variables: An Application to Cancer.Medical decision making : an international journal of the Society for Medical Decision Making · 2024
    Article
  14. Causal Relationships Between Screen Use, Reading, and Brain Development in Early Adolescents.Advanced science (Weinheim, Baden-Wurttemberg, Germany) · 2024
    Article
  15. Article
  16. Linear and Nonlinear Associations Between Vitamin D and Grip Strength: A Mendelian Randomization Study in UK Biobank.The journals of gerontology. Series A, Biological sciences and medical sciences · 2023
    Article
  17. Article
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  19. Article
  20. Article
4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

4 authors.

Rachael A HughesFrom the Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom.
Neil M DaviesFrom the Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom.
George Davey SmithFrom the Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom.
Kate TillingFrom the Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, United Kingdom.

Funding

Medical Research Council MC\_UU\_00011/1Medical Research Council MC_UU_00011/1Medical Research Council MC\_UU\_00011/3Medical Research Council MC_UU_00011/3Wellcome Trust
6 · The paper itself

Abstract

Participants in epidemiologic and genetic studies are rarely true random samples of the populations they are intended to represent, and both known and unknown factors can influence participation in a study (known as selection into a study). The circumstances in which selection causes bias in an instrumental variable (IV) analysis are not widely understood by practitioners of IV analyses. We use directed acyclic graphs (DAGs) to depict assumptions about the selection mechanism (factors affecting selection) and show how DAGs can be used to determine when a two-stage least squares IV analysis is biased by different selection mechanisms. Through simulations, we show that selection can result in a biased IV estimate with substantial confidence interval (CI) undercoverage, and the level of bias can differ between instrument strengths, a linear and nonlinear exposure-instrument association, and a causal and noncausal exposure effect. We present an application from the UK Biobank study, which is known to be a selected sample of the general population. Of interest was the causal effect of staying in school at least 1 extra year on the decision to smoke. Based on 22,138 participants, the two-stage least squares exposure estimates were very different between the IV analysis ignoring selection and the IV analysis which adjusted for selection (e.g., risk differences, 1.8% [95% CI, -1.5%, 5.0%] and -4.5% [95% CI, -6.6%, -2.4%], respectively). We conclude that selection bias can have a major effect on an IV analysis, and further research is needed on how to conduct sensitivity analyses when selection depends on unmeasured data.

Indexed as

Confounding Factors, EpidemiologicEpidemiologic MethodsSelection BiasCausalityHumansTreatment Outcome

Identifiers

PMID30896457
PMCPMC6525095

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Registered trials

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.