Anaemia in patients with acute ischaemic stroke (AIS) is associated with an increased risk of death both in the short and long term, as shown in a local study.
Analysis of data from the Singapore Stroke Registry showed that AIS patients with severe anaemia had the highest risk of all-cause mortality. Compared with patients with normal-range haemoglobin levels, those with severe anaemia had a nearly twofold higher risk of all-cause mortality at 30 days (hazard ratio [HR], 1.99, 95 percent confidence interval [CI], 1.92–2.06), and this risk increase persisted at 1 year (HR, 1.73, 95 percent CI, 1.66–1.81) and 5 years (HR, 1.52, 95 percent CI, 1.41–1.64). [Front Stroke 2026;doi:10.3389/fstro.2026.1859301]
Mild anaemia also carried an increased risk of all-cause mortality, with a risk increase of 38 percent at 30 days (HR, 1.38, 95 percent CI, 1.34–1.42), 33 percent at 1 year (HR, 1.33, 95 percent CI, 1.29–1.38), and 28 percent at 5 years (HR, 1.28, 95 percent CI, 1.21–1.35) when compared with normal-range haemoglobin levels.
At 10 years, the risk of all-cause mortality was attenuated and became insignificant among AIS patients with severe anaemia (HR, 1.13, 95 percent CI, 0.95–1.34) but remained elevated among those with mild anaemia (HR, 1.16, 95 percent CI, 1.04–1.31).
According to the authors, the difference in the 10-year risk of all-cause mortality between AIS patients with severe anaemia and those with mild anaemia “may partly reflect survivorship bias, where those patients with severe anaemia who survived to later timepoints represented a specific subgroup already at lower baseline risk.”
Severe anaemia may have resulted from correctable events, such as bleeding, triggering prompt evaluation and treatment, whereas mild anaemia may be more likely to remain untreated, potentially contributing to the persistence of increased long-term risk of all-cause mortality, they explained.
“Regardless, these findings highlight the need to consider anaemia as a dynamic, longitudinal clinical factor post-AIS, rather than a single baseline measurement,” the authors said.
The analysis included 56,884 AIS patients (median age 68 years, 57 percent male), of whom 66.8 percent had no anaemia, 15.7 percent had mild anaemia, 12.2 percent had severe anaemia, and 5.3 percent had polycythaemia.
There was no excess risk of mortality observed among AIS patients with polycythaemia at any time point when compared with those who had normal-range haemoglobin levels.
Managing anaemia in practice
Dr Benjamin Tan
Vascular Neurologist at the National University Hospital, Singapore, and Adjunct Assistant Professor at the Yong Loo Lin School of Medicine, National University of Singapore“The clinical takeaway is straightforward: anaemia at the time of an AIS is a prognostic signal worth paying attention to. Rather than treating the haemoglobin number alone, clinicians should ask why the patient is anaemic and whether there is a modifiable underlying condition that deserves attention,” Tan told MIMS.
“Anaemia may reflect acute blood loss or an underlying condition such as nutritional deficiency, chronic kidney disease, inflammation, infection, or malignancy. These conditions may themselves have important implications for prognosis and subsequent management,” he explained.
Tan, however, pointed out that not every stroke patient with mildly reduced haemoglobin requires an extensive battery of investigations.
“I would favour a proportionate, clinically directed approach. The intensity of investigation should depend on factors such as the severity of the anaemia, whether it is new or longstanding, the red-cell indices and other laboratory abnormalities, the patient’s symptoms and comorbidities, and whether there are features suggesting bleeding or systemic disease. Persistent, unexplained, progressive or severe anaemia would warrant more active investigation,” he said.
For patients with mild anaemia, “mild” should not be equated with “unimportant,” Tan cautioned. “Our findings suggest that even modest reductions in haemoglobin identify a group with higher long-term mortality, so potentially reversible causes should not be overlooked.”
As for “patients with severe anaemia, I would have a lower threshold to establish the cause promptly, particularly to exclude active bleeding or significant underlying systemic disease,” he added.
Finally, Tan emphasized that while the study highlights a clear association between anaemia and mortality in AIS, the findings do not prove that anaemia itself causes the excess mortality or that correcting the haemoglobin will improve stroke outcomes.
“At present, there is no well-established stroke-specific haemoglobin threshold at which transfusion improves neurological or survival outcomes, and determining whether acute or gradual correction of anaemia can modify outcomes in AIS remains an important question for future prospective trials,” he said.