Impact of hemoglobin levels and anemia on mortality in acute stroke: analysis of UK regional registry data, systematic review and meta-analysis

Background: The impact of hemoglobin levels and anemia on stroke mortality remains controversial. We aimed to systematically assess this association and quantify the evidence.

Methods and Results: We analysed data from a cohort of 8,013 stroke patients (mean (sd) 77.81±11.83 years) consecutively admitted over 11 years (January 2003–May 2015) using a UK Regional Stroke Register. The impact of hemoglobin levels and anemia on mortality was assessed by sex-specific values at different time points (7-day, 14-day, 1-month, 3-month, 6-month, 1 year), using multiple regression models controlling for confounders. Anemia was present in 24.5% of the cohort on admission and was associated with increased odds of mortality at most of the time points examined up to 1 year following stroke. The association was less consistent for males with hemorrhagic stroke. Elevated haemoglobin was also associated with increased mortality, mainly within the first month. We then conducted a systematic review using the EMBASE and Medline databases. Twenty studies met the inclusion criteria. When combined with the cohort from the current study, this gave a pooled population of 29,943 patients with stroke. The evidence base was quantified in a meta-analysis. Anemia on admission was found to be associated with an increased risk of mortality in both ischemic stroke (8 studies); OR 1.97(1.56– 2.47) and hemorrhagic stroke (4 studies); OR 1.46(1.23–1.74).

Conclusions: There is strong evidence that patients with anemia have increased mortality in stroke. Targeted interventions in this patient population may improve outcomes and therefore require further evaluation.