Genetically Elevated Neutrophil Count Is Associated with Poor Outcome Following Ischemic Stroke: A Mendelian Randomization Study.

The aim of this study was to investigate the association between genetically proxied white blood cell (WBC) subtype counts and functional outcome following ischemic stroke. Genetic proxies for counts of neutrophils, lymphocytes, monocytes, eosinophils, and basophils were identified from the Blood Cell Consortium genome-wide association study meta-analysis (N = 562,243 European participants). A poor post-stroke functional outcome was defined as a modified Rankin Scale (mRS) score > 2 at 3 months. Summary-level genetic associations with mRS > 2 (mRS 0-2 vs. 3-6) were obtained from the Genetics of Ischemic Stroke Functional Outcome network (N = 6021). Associations of genetically proxied WBC counts with functional outcome after ischemic stroke were estimated using the random-effects inverse variance weighted method. In univariable MR analysis, genetically proxied higher neutrophil count was nominally associated with poor functional outcome following ischemic stroke (OR = 1.33, 95% CI = 1.05-1.70; P = 0.020). This association was consistent in multivariable MR analysis adjusting for genetic associations with all other WBC subtypes (OR = 1.45, 95% CI = 1.06-1.99; P = 0.021). There were no associations between any other WBC subtypes counts and functional outcome following ischemic stroke. Our findings provide genetic evidence that genetically proxied neutrophil count was associated with poor functional outcome following ischemic stroke. Future studies are needed to replicate this finding and to investigate the molecular mechanisms underlying this association.