Impact of nonrandom selection mechanisms on the causal effect estimation for two-sample Mendelian randomization methods.

ABSTRACT: Nonrandom selection in one-sample Mendelian Randomization (MR) results in biased estimates and inflated type I error rates only when the selection effects are sufficiently large. In two-sample MR, the different selection mechanisms in two samples may more seriously affect the causal effect estimation. Firstly, we propose sufficient conditions for causal effect invariance under different selection mechanisms using two-sample MR methods. In the simulation study, we consider 49 possible selection mechanisms in two-sample MR, which depend on genetic variants (G), exposures (X), outcomes (Y) and their combination. We further compare eight pleiotropy-robust methods under different selection mechanisms. Results of simulation reveal that nonrandom selection in sample II has a larger influence on b

SUBMITTER: Yu Y 

PROVIDER: S-EPMC8963545 | biostudies-literature | 2022 Mar

REPOSITORIES: biostudies-literature