Mortality Lowest at Hemoglobin Concentrations Above WHO Thresholds

TUESDAY, Sept. 22, 2026 (HealthDay News) — Mortality is lowest at hemoglobin concentrations above current World Health Organization (WHO) thresholds, according to a study published online Sept. 8 in the Annals of Internal Medicine.

Malek Ahmad, M.B.B.S., from the University of Glasgow in the United Kingdom, and colleagues conducted a prospective-based cohort study in the United Kingdom involving 502,188 adults to examine associations between baseline hemoglobin concentration and long-term mortality by age and sex. Hemoglobin concentration was measured in 477,876 participants.

The researchers identified a U-shaped association for all-cause mortality with hemoglobin concentration, with the lowest risk seen at 1 to 3 g/dL above the WHO threshold. The 10-year standardized cumulative incidence (SCI) was 4.5 percent in the reference group versus 12.5 percent among participants more than 2 g/dL below the threshold, in the primary adjusted model; the adjusted hazard ratio was 2.87 during the entire follow-up. The 10-year SCI was 5.3 percent and the adjusted hazard ratio was 1.18 among those 0 to 1 g/dL above the threshold. In women younger than 60 years, the associations were less consistent. Similar patterns were seen for cardiovascular and cancer mortality at low and borderline concentrations, but they were attenuated at higher concentrations.

“Our observations suggest that values up to 1 g/dL above the current WHO definition for anemia (borderline anemia) may warrant investigation rather than automatic reassurance, particularly in people with a high prevalence of iron deficiency, such as older adults and those with cardiovascular disease,” the authors write.

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