Higher Total White Blood Cell and Neutrophil Counts Are Associated With Increased Stroke Mortality Risk: The Guangzhou Biobank Cohort Study

Abstract Background: To investigate the relations of white blood cell (WBC) count and its dynamic change with future stroke mortality risk in a relatively healthy elderly population.Methods: A total of 27811 participants without stroke history at baseline were included and followed up for an average of 11.5 (SD=2.3) years. After review of available records, 399 stroke (277 ischaemic and 172 haemorrhagic) deaths were recorded among all-cause mortality. Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).Results: Compared with the lowest quartile, the highest quartile of WBC count showed 53% and 67% increased mortality risk for total (adjusted HR [aHR]=1.53, 95% CI 1.16-2.02, P=0.003) and haemorrhagic (aHR=1.67, 95% CI 1.10-2.67, P=0.03) stroke, respectively; the highest neutrophil count showed 45% and 65% increased mortality risk for total (aHR=1.45, 95% CI 1.10-1.89, P=0.008) and ischaemic (aHR=1.65, 95% CI 1.10-2.47 P=0.02) stroke. The same results found for total and ischaemic stroke but not for haemorrhagic stroke were observed for both WBCs and neutrophils within the normal range level after further C-reactive protein (CRP) adjustment. Compared with the stable group, the 25% increased groups of both WBCs (aHR=1.60, 95% CI 1.07-2.40, P=0.02) and neutrophils (aHR=1.45, 95% CI 1.02-2.05, P =0.04) showed 60% and 45% increased stroke mortality risk, respectively.Conclusions: These findings support the role of WBCs, especially neutrophils, as simple, inexpensive and readily available predictors of future stroke mortality in an elderly population. Trial registration: The Guangzhou Medical Ethics Committee of the Chinese Medical Association approved the study.