Figure 1

Causal mediation framework. (a) The effect of exposure X on outcome Y without taking into account mediator M is known as the “total effect”. (b) The effect of X on Y not via M is known as the “direct effect”, and the effect through M is the “indirect effect”. (c) X, M, Y are body mass index /waist-to-height ratio, glycoprotein acetyls (GlycA) and retinal arteriolar/venular calibre in the current study. Confounders included in the analysis were not shown in the figure.