Anemia status, hemoglobin concentration and outcome after acute stroke: a cohort study

Abstract

BackgroundIn the setting of an acute stroke, anemia has the potential to worsen brain ischemia, however, the relationship between the entire range of hemoglobin to long-term outcome is not well understood.MethodsWe examined the association between World Health Organization-defined admission anemia status (hemoglobin<13 in males, <12 g/dl in women) and hemoglobin concentration and 1-year outcome among 859 consecutive patients with acute stroke (ischemic or intracerebral hemorrhage).ResultsThe mean baseline hemoglobin concentration was 13.8 ± 1.7 g/dl (range 8.1 - 18.7). WHO-defined anemia was present in 19% of patients among both women and men. After adjustment for differences in baseline characteristics, patients with admission anemia had an adjusted OR for all-cause death at 1-month of 1.90 (95% CI, 1.05 to 3.43) and at 1-year of 1.72 (95% CI, 1.00 to 2.93) and for the combined end-point of disability, nursing facility care or death of 2.09 (95% CI, 1.13 to 3.84) and 1.83 (95% CI, 1.02 to 3.27) respectively. The relationship between hemoglobin quartiles and all-cause death revealed a non-linear association with increased risk at extremes of both low and high concentrations. In logistic regression models developed to estimate the linear and quadratic relation between hemoglobin and outcomes of interest, each unit increment in hemoglobin squared was associated with increased adjusted odds of all-cause death [at 1-month 1.06 (1.01 to 1.12; p = 0.03); at 1-year 1.09 (1.04 to 1.15; p < 0.01)], confirming that extremes of both low and high levels of hemoglobin were associated with increased mortality.ConclusionsWHO-defined anemia was common in both men and women among patients with acute stroke and predicted poor outcome. Moreover, the association between admission hemoglobin and mortality was not linear; risk for death increased at both extremes of hemoglobin.

Impact of Hemoglobin Levels and Anemia on Mortality in Acute Stroke: Analysis of UK Regional Registry Data, Systematic Review, and Meta‐Analysis

“…After detailed screening, 20 studies were included in our systematic review; the flow chart of study selection is shown in Figure 4, and Tables 5 and 6 show the key features of the selected studies. Overall, 10 studies assessed the impact of anemia on stroke1, 2, 10, 16, 17, 18, 19, 20, 21, 22 and 10 evaluated the association between stroke and hemoglobin levels 6, 7, 8, 9, 23, 24, 25, 26, 27, 28. In terms of study design, 3 were retrospective cohort studies,1, 16, 20 13 were prospective cohort studies,2, 6, 7, 8, 9, 10, 17, 18, 19, 22, 23, 24, 25 and 2 were secondary analyses of randomized control trials 27, 28.…”

“…There were also 2 studies that did not state the design 21, 26. There was a high degree of diversity in geographic location, with cohorts from Germany,8, 19, 25 Switzerland,16, 20 the United States,18, 24 the People's Republic of China,2, 22 Canada,23, 28 India,6 Israel,10 the Republic of Korea,9 Denmark,21 Taiwan,17 the United Kingdom,26 and Poland 7. In addition, 2 studies were conducted across multiple countries 1, 27.…”

“…Imaging (computed tomography, magnetic resonance imaging, or both) was used in 17 studies,1, 2, 6, 7, 8, 10, 17, 18, 19, 20, 21, 22, 23, 24, 25, 27, 28 1 study relied on clinical evaluation alone,26 and 2 did not state the method used 9, 16. The methods used to ascertain mortality also varied.…”

“…Eleven studies used the World Health Organization definition of anemia as hemoglobin cutoffs,2, 8, 10, 16, 17, 18, 19, 20, 21, 22, 24 7 used prespecified values,1, 9, 23, 25, 26, 27, 28 and 2 did not specify the values used 6, 7. By using prespecified thresholds in constructing categorical comparisons for anemia, it is possible that cut points have been drawn up that favor statistically significant findings.…”

“…By using prespecified thresholds in constructing categorical comparisons for anemia, it is possible that cut points have been drawn up that favor statistically significant findings. Eighteen studies adjusted for potential confounders1, 2, 7, 8, 9, 10, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27; however, there was great variation in terms of the variables adjusted for. These included age and National Institutes of Health Stroke Scale1 as well as age, sex, insurance status, smoking, time to treatment, type of intervention, prestroke medication, body mass index, blood pressure, heart rate, Trial of Org 10172 Acute Stroke Treatment criteria classification, metabolic parameters, and comorbidities 20.…”