Fig. 1. Study overview.
A Schematic diagram of an MR analysis. Since genetic alleles are independently segregated and randomly assigned, SNPs are not associated with confounding factors that may bias estimates from observational studies. Three assumptions of MR are as follows: (1) the selected instrument is predictive of the exposure, (2) the instrument is independent of confounding factors, and (3) there is no horizontal pleiotropy (the instrument is associated with the outcome only through the exposure). B The study design overview of the current study. MR Mendelian randomization, GWAS genome-wide association studies, AD Alzheimer’s disease, PD Parkinson’s disease, ALS amyotrophic lateral sclerosis, LD linkage disequilibrium, SNP single nucleotide polymorphism.
