Causal inference in epidemiology through Mendelian randomization & Mendelian Randomisation-Phenome Wide Association Studies: Opportunities and Challenges

The two speakers for the SA Branch May meeting were Dr Beben Benyamin and Dr Ang Zhou, both from the Centre for Precision Health, University of South Australia. This was a joint meeting with the South Australian Epidemiology Group. Dr Benyamin uses statistics applied to large-scale ‘omics’ data to dissect the genetic mechanisms underlying human complex traits and diseases. Dr Benyamin’s talk “Causal Inference in epidemiology through Mendelian randomization” described Mendelian Randomization (MR), a statistical method that provides a framework to mimic a randomised controlled trial, providing an estimate of the causal effect of a risk factor on disease. Mendelian randomization analyses (MR) use genetic variants as proxy markers for the risk factor of interest. This approach exploits the fact that the assignment of genotype is random with respect to confounders. MR studies have increased due to the discovery of potential genetic variants from genome wide association studies. The talk covered the origin of the method, basic principles and some applications to infer the causal effect of the risk factor on the disease.

Dr Ang applies methodologies in genetic epidemiology to understand causal associations between modifiable lifestyle factors and health outcomes. His research also involves understanding the gene-environment interplay on health outcomes. His talk “MR-PheWAS: Opportunities and Challenges” followed on from Dr Benyamin’s talk by describing phenome-wide association studies (PheWAS), an extension to Mendelian randomization. MR-PheWAS is a hypothesis-free approach to screen for diseases/phenotypes associated with the risk factor of interest, which has the capacity to capture novel associations and provide insights into disease mechanisms. Dr Ang used the example of BMI genetic associations to highlight the opportunities and challenges of the method.

A dinner was held after the meeting at Jasmin Indian Restaurant, 31 Hindmarsh Square, Adelaide.

Lan Kelly