Woolf et als GWAS by subtraction is not useful for cross-generational Mendelian randomization studies

TL;DR

This paper critically evaluates Woolf et al.'s GWAS by subtraction method, arguing it is ineffective and inappropriate for cross-generational Mendelian randomization studies due to fundamental methodological issues.

Contribution

The paper provides a critical analysis of a new GWAS method, highlighting its limitations and clarifying the correct parameters for cross-generational MR research.

Findings

GWAS by subtraction is not efficient for cross-generational MR.

The method targets the wrong parameter for GWAS in this context.

The estimator derived is neither suitable nor effective for the intended purpose.

Abstract

Mendelian randomization (MR) is an epidemiological method that can be used to strengthen causal inference regarding the relationship between a modifiable environmental exposure and a medically relevant trait and to estimate the magnitude of this relationship1. Recently, there has been considerable interest in using MR to examine potential causal relationships between parental phenotypes and outcomes amongst their offspring. In a recent issue of BMC Research Notes, Woolf et al (2023) present a new method, GWAS by subtraction, to derive genome-wide summary statistics for paternal smoking and other paternal phenotypes with the goal that these estimates can then be used in downstream (including two sample) MR studies. Whilst a potentially useful goal, Woolf et al. (2023) focus on the wrong parameter of interest for useful genome-wide association studies (GWAS) and downstream cross-generational MR studies, and the estimator that they derive is neither efficient nor appropriate for such use.