Objectives Our primary aim was to study the influence of common F11, F12, KLKB1, and KNG1 variants on factor (F) XI activity and FXI, FXII, prekallikrein (PK) and high-molecular-weight kininogen (HMWK) antigen levels, as well as the risk of myocardial infarction and ischemic stroke.
Results- After applying a Bonferroni correction for multiple testing, the Mendelian randomization analysis supported a causal effect of higher, genetically determined FXI levels on risk of any IS (odds ratio [OR] per 1-unit increase in natural logarithm-transformed FXI levels, 2.54; 95% CI, 1.68-3.84; P=1×10<sup>-5</sup>) but not myocardial infarction (OR, 1.01; 95% CI, 0.76-1.34; P=0.94) or intracerebral hemorrhage (OR, 1.81; 95% CI, 0.44-7.38; P=0.41).