Figure 1. Directed acyclic flowchart of MR process for investigating the causal relationship between body fat indexes and the risk of BCa.
Instrumental variable (IV) assumptions: (1) IVs must be strongly associated with body fat indexes (p < 5 ×10−8); (2) IVs must not be correlated with any unmeasured confounders of body fat indexes versus BCa relationship; (3) IVs should only affect the risk of BCa via body fat indexes. SNPs, single-nucleotide polymorphisms; BCa, bladder cancer; IVW, inverse variance weighted; WM, weighted median.