Fig. 1

The parallel relationship between the design flow charts of the three studies. A Mendelian randomization (MR): It uses randomly assigned the genetic variant to be equivalent to the subgroups of randomized controlled trial (RCT). B RCT: It also divides the population into different subgroups according to the way of random distribution, so that the intervention between groups is different. C Prospective cohort study: It is an observational research method that divides a group of cohorts into exposure group and non-exposure group according to whether they are exposed to a certain research factor to judge whether there is a correlation between the exposure factor and disease