Anaemia linked to increased stroke mortality

By Bianca Nogrady
Anaemia and elevated haemoglobin are both associated with increased mortality from stroke, according to a systematic review and meta­-analysis.

A pooled analysis of 29,943 stroke patients showed those with anaemia on admission – defined according to the WHO criteria as haemoglobin levels less than 120 g/L in women and less than 130 g/L in men – had a 97% higher mortality after ischaemic stroke and 46% higher mortality after haemorrhagic stroke.

Researchers also observed that although elevated haemoglobin predicted short-­term mortality in patients with ischaemic stroke, the association was less consistent for haemorrhagic stroke, according to their paper published in the Journal of the American Heart Association. 

‘Although anemia has been independently associated with increased mortality in a variety of conditions including chronic kidney disease, heart failure, and acute coronary syndromes, observational studies investigating the association between anemia and mortality in stroke have shown conflicting results,’ the authors wrote.

They noted five studies reporting no significant association between anaemia and stroke mortality, but these could not be incorporated into the meta­-analysis of their systematic review because odds ratios were not given.

Commenting on the study, Professor Craig Anderson said low haemoglobin was generally a marker of a sicker, frailer patient, which would contribute to a higher stroke mortality.

‘High haemoglobin is also a measure of the severity of the disease, because haemoglobin levels increase as one gets dehydrated or stressed, while one’s haemoglobin can also go down if you are seriously unwell or go up when on a variety of medications for chronic disease,’ said Professor Anderson, Professor of Stroke Medicine at The University of Sydney.

However, Professor Anderson told Medicine Today, there was not an easy therapeutic strategy that flows on from the findings of this meta-­analysis. 

‘The recommendation for clinical practice would be to just call attention to haemoglobin levels as one other marker of risk stratification or prognosis; one other factor that just indicates a particular patient is more at risk of an adverse outcome.’
J Am Heart Association 2016; doi: 10.1161/JAHA.115.003019.