GGT1 and susceptibility to pneumonia measurement: Whilst there was some evidence for a causal relationship between GGT and pneumonia susceptibility using an MR approach (supported five models being directionally consistent in GGT exerting an odds increasing effect on pneumonia, Fig. 4b, Supplementary Data 16), only the weighted mode and weighted median models were statistically significant – OR per SD GGT = 1.08 [95% CI: 1.02, 1.16], P = 0.01 (Weighted median).