Borderline low hemoglobin levels, usually considered normal, linked to a higher risk of death

A prospective cohort study found that adults whose hemoglobin levels were 1 to 3 g/dL above the World Health Organization’s (WHO) current anemia thresholds had lower mortality compared with those whose hemoglobin levels were both below and above this range. While the findings do not warrant updated anemia thresholds, they do suggest that further investigation of borderline anemia is warranted. The study is published in Annals of Internal Medicine.

Researchers from the University of Glasgow evaluated the association between hemoglobin concentration and long-term mortality among 502,188 adults enrolled in the UK Biobank.

Hemoglobin concentrations were compared with the WHO’s sex-specific anemia thresholds, and investigators examined deaths from any cause, cardiovascular disease and cancer over a median follow-up of 13.6 years. They found a U-shaped relationship between hemoglobin levels and mortality, with the lowest risk occurring at hemoglobin concentrations 1 to 3 g/dL above current WHO anemia thresholds.

The authors conclude that the findings may help clinicians better interpret borderline hemoglobin levels and identify individuals at increased risk.

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