Hundreds of thousands of people in the UK may have a hidden blood condition that elevates their risk of serious illness and early death, according to a significant study.
Researchers from the University of Glasgow analyzed data from nearly half a million UK Biobank participants over a decade, finding that individuals with 'borderline anemia'—those whose hemoglobin levels are low but still within current diagnostic ranges—face an increased risk of cardiovascular disease, cancer, and premature death. The findings were published in the journal Annals of Internal Medicine.
Anaemia, often caused by iron deficiency, is typically diagnosed when hemoglobin levels fall below thresholds set by the World Health Organization (WHO). However, these guidelines have remained unchanged for 50 years. The new study suggests these thresholds may miss individuals who are still at risk.
"Risk already starts to increase with borderline anaemia, before haemoglobin falls below the current WHO threshold," said Dr. Malek Ahmad, a clinician-scientist at the University of Glasgow and lead author of the study. "Currently, many doctors do not even recognise a person has anaemia until its moderately severe. Showing that borderline anaemia is associated with increased risk and a high prevalence of iron deficiency should encourage investigation and treatment of a broad range of patients with mild/borderline anaemia."
Haemoglobin is the protein in red blood cells responsible for carrying oxygen throughout the body. The study found that extreme levels, both too high and too low, were associated with the highest risks. Individuals with low, but still normal, hemoglobin levels were found to be more likely to die early compared to those with higher levels.
Anaemia is most commonly linked to iron deficiency, which hinders the body's ability to produce sufficient healthy red blood cells. Deficiencies in vitamin B12 or folate can also be contributing factors. Common symptoms include fatigue, pale skin, irritability, and a rapid heartbeat. While dietary intake is a primary factor, heavy menstrual periods and pregnancy are also frequent causes. Chronic conditions like kidney disease and inflammatory disorders can also lead to anaemia. Certain medications, including some heartburn drugs like omeprazole, calcium and zinc supplements, and some antibiotics, can interfere with iron absorption.
The researchers emphasized that their findings do not definitively prove that low hemoglobin itself directly causes earlier death. They plan to investigate whether diagnostic guidelines should be updated to incorporate factors such as diet, stress, and obesity, which could aid clinicians in identifying at-risk individuals sooner.
Globally, an estimated two billion people have iron deficiency, with 1.2 billion having developed iron-deficiency anaemia. In the UK, approximately three percent of men and eight percent of women are estimated to have the condition, and over 57,000 hospital admissions annually are attributed to anaemia.
Treatment for anaemia is often straightforward. Daily iron supplements, which can cost as little as 10 pence per pill, can be effective in restoring iron levels. Consuming more iron-rich foods, such as dark leafy greens, fortified cereals, and red meat, can also be beneficial.
These findings emerge amid growing concerns over an increase in hospital admissions in the UK due to deficiencies in essential vitamins and minerals. Earlier this year, NHS figures indicated a substantial rise in patients admitted with iron-deficiency anaemia and illnesses linked to a lack of B vitamins. The Royal College of GPs has expressed concern, noting that the cost-of-living crisis may be making nutritious diets increasingly unaffordable for some individuals.