Elevated red blood cell distribution width predicts mortality in persons with known stroke

doi:10.1016/j.jns.2008.10.024

Journal of the Neurological Sciences

Volume 277, Issues 1–2, 15 February 2009, Pages 103-108

https://doi.org/10.1016/j.jns.2008.10.024 Get rights and content

Abstract

Background

Red cell distribution width (RDW) is a hematological parameter routinely obtained as part of the complete blood count. Recently, RDW has emerged as a potential independent predictor of clinical outcome in patients with established cardiovascular disease. However, little is known about the role of RDW as a prognosticator among persons with stroke, especially with regard to an incontrovertible endpoint like mortality. We assessed the association of RDW with stroke, and its effect on mortality among persons with stroke.

Methods

Data from the National Health and Nutrition Examination Survey (NHANES) a nationally representative sample of United States adults were analyzed. The study population consisted of 480 individuals aged ≥ 25 years with a baseline history of stroke followed-up from survey participation (1988–1994) through mortality assessment in 2000. Proportional hazard regression (Cox) was utilized to explore the independent relationship between RDW and mortality after adjusting for potential confounders.

Results

Among the cohort, 52.4% were female, 64% aged ≥ 65 years. Mean RDW was significantly higher among persons with stroke compared to individuals without a stroke (13.7% vs.13.2%,p < 0.001). Baseline RDW was higher among persons with known stroke who later died vs. remained alive (13.9% vs.13.4%,p < 0.001). After adjusting for confounders, those with elevated RDW (fourth vs. first quartile) were more likely to have experienced a stroke (OR 1.71, CI = 1.20–2.45). Higher RDW level (fourth vs. first quartile) among those with known stroke independently predicted subsequent cardiovascular deaths (HR = 2.38 and CI = 1.41–4.01) and all-cause deaths (HR = 2.0, CI = 1.25–3.20).

Conclusions

Elevated RDW is associated with stroke occurrence and strongly predicts both cardiovascular and all-cause deaths in persons with known stroke.

Introduction

The red blood cell distribution width, or RDW, is a measure of the variation of red blood cell volume that is reported as part of a standard complete blood count (CBC). Higher RDW values indicate greater variation in size. Increased RDW has been associated with several medical disorders and nutritional deficiencies and recently hospital admission was shown to be a prognosticator of early outcomes following hospitalization for general medical conditions [1]. Furthermore, RDW was noted to be a strong independent predictor of morbidity and mortality in patients with prior myocardial infarction, heart failure and end stage renal disease [2], [3], [4]. Several have speculated that higher levels of RDW may reflect an underlying inflammatory state, which is associated with adverse clinical outcomes and leads to impaired erythrocyte maturation.

We are unaware of any studies that have looked at the prognostic value of RDW among stroke patients. Since RDW is widely available to clinicians as part of the complete blood count and therefore incurs no additional costs, (in contrast to other novel markers of cardiovascular risk) if found to be an independent prognosticator of stroke outcomes, this might be of immense clinical relevance. In this study we aimed to assess the association of stroke with RDW and the ability of baseline RDW to predict cardiovascular and all-cause mortality among individuals with a known history of stroke.

Section snippets

Subjects and methods

This study utilized data from a nationally representative sample of the civilian, non-institutionalized US population. This data was collected by the Centers for Disease Control and Prevention’s third National Health and Nutrition Examination Surveys [NHANES III] conducted at 89 survey locations between January 1, 1988, and December 31 1994. This survey utilized a complex multistage cluster design and over-sampled persons 60 years and older, non-Hispanic black individuals, and Mexican American

Sample characteristics

The socio-demographic and clinical characteristics of the study sample can be found in Table 1. Among the sample of individuals with a known stroke, 52.4% were female and persons aged 65 years or older accounted for 64.0% of the sample. Mean duration since stroke occurrence among those with a stroke was 8.1 years. The analysis of mean RDW demonstrated higher mean RDW values among individuals with a stroke compared to individuals without a stroke (13.69% vs.13.24%, p < 0.001).

RDW and stroke prevalence

Bivariate analysis

Discussion

In this nationally representative cohort, we found that baseline RDW level was significantly higher among persons with known stroke compared to those without a history of stroke, and that baseline RDW also independently predicted both cardiovascular and all-cause mortality within 12 years of the initial evaluation. Specifically, among those who had experienced a stroke at baseline, RDW in the highest quartile compared to the lowest quartile conferred at least twice the risk of dying from a