Haemoglobin concentration predicts mortality risk in adults

Haemoglobin concentrations are associated with mortality, which is increased when concentrations are below or beyond the range of 1‒3 g/dL above current World Health Organization (WHO) thresholds (men, <13.0 g/dL; women, <12.0 g/dL), suggests a study.

A total of 502,188 adults (median age 58 years, 54.4 percent women) recruited from 2006 to 2010 in the UK were included in this prospective cohort study. Of these, 477,876 (95.2 percent) had their haemoglobin concentration measured. The researchers stratified analyses by age (<60 vs ≥60 years) and sex, with a median follow-up of 13.6 years.

All-cause mortality demonstrated a U-shaped relationship with haemoglobin concentration. The lowest mortality risk was seen at 1‒3 g/dL above the WHO threshold.

In the primary adjusted model, the 10-year standardized cumulative incidence (SCI) was 4.5 percent in the reference group and 12.5 percent in participants with haemoglobin concentrations >2 g/dL below the WHO threshold (absolute risk difference [ARD], 8.1 percentage points, 95 percent confidence interval [CI], 6.7‒9.4; adjusted hazard ratio [aHR], 2.87, 95 percent CI, 2.54‒3.25).

Among participants with concentrations of 0‒1 g/dL above the threshold, the 10-year SCI was 5.3 percent (ARD, 0.8 percentage points, 95 percent CI, 0.7‒1.0; aHR, 1.18, 95 percent CI, 1.15‒1.21).

These associations were less consistent in women aged <60 years. Cardiovascular and cancer mortality patterns were comparable at low and borderline concentrations but lessened at higher concentrations.

“These hypothesis-generating findings should not define new thresholds but may inform clinical interpretation and evaluation of borderline haemoglobin concentration values,” the researchers said.