White blood cell count and C-reactive protein are independent predictors of mortality in the oldest old

Abstract

Background: White blood cell (WBC) count is, like C-reactive protein (CRP), a clinical marker of inflammation and predicts cardiovascular disease and mortality in middle-aged populations. Limited data exist on the association between WBC count and mortality in the oldest old. Moreover, because CRP and WBC count are closely linked, it is not known whether WBC count and CRP are independent risk factors for mortality. We assessed the independent predictive value of WBC count and CRP levels in relation to mortality, both vascular and nonvascular, in very old participants.

Methods: A total of 599 women and men were evaluated longitudinally in the Leiden 85-plus Study. Blood samples and medical information were collected at age 85, and all participants were visited annually until age 90 or death. Mortality risks were estimated with Cox proportional hazard models.

Results: Increasing WBC count was associated with an increased risk for all-cause mortality (hazard ratio, HR [95% confidence interval, CI] = 1.26 [1.15-1.38]) after adjustment for sex and smoking status. CRP levels were also associated with an increased risk for mortality (HR [95% CI] = 1.22 [1.10-1.35]). The association between increasing WBC count and mortality remained significant after adjustment for CRP levels (HR [95% CI] = 1.20 [1.09-1.33]), whereas also the relation between increasing CRP levels and mortality remained significant after adjustment for WBC count (HR [95% CI] = 1.17 [1.05-1.30]).

Conclusion: Our results suggest that WBC count and CRP levels both independently predict mortality in the oldest old.