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What role for iron treatment in kidney disease patients?

22 June 2023

People living with chronic kidney disease (CKD) can have low levels of iron, even though they may not meet the medical definition of anaemia. Low iron levels are linked to physical symptoms, including feeling tired and muscle weakness. The Iron and Muscle study looked at whether iron supplementation and exercise could improve exercise capacity in CKD patients who had reduced iron levels.

Looking at low iron levels in kidney disease patients

The Iron and Muscle study, led by Dr Sharlene Greenwood and Dr Kate Bramham from King’s College Hospital NHS Trust and supported by Kidney Research UK, compared the impact of treatment with IV iron or placebo (no treatment) and exercise on patients with stage 3-4 chronic kidney disease (CKD) not receiving dialysis, who had reduced iron levels but were not considered anaemic.

The study followed 75 individuals who were randomly assigned to a placebo or iron-treatment group. Dr Greenwood and her team assessed a range of measures associated with iron deficiency; including how far the patients could walk in six minutes at the start of the study, and at four and 12 weeks. Patients who joined the study were offered either in-person or on-line exercise training from week 4. 

What is iron and why is it important?

Iron is a mineral that we gain through eating certain foods, including red meat and bean. Iron is very important for production of red blood cells, which carry oxygen around the body and myoglobin, providing oxygen to muscles. Low blood iron is linked to reduced energy levels and muscle strength. When iron levels are very low, anaemia is diagnosed, and treatment can be given.  

People living with kidney disease can be iron deficient, but not anaemic. The iron and muscle study looked at kidney disease patients with iron levels that were reduced, but not low enough to be classed as anaemia. 

Clues for future research

Although this study didn’t show an improvement in the 6-minute walking distance in the iron-treated group, investigators found increases in measures of blood iron and haemoglobin at 12 weeks in these patients.

The researchers also reported an indication of improved walking capacity in the iron-treated patients also receiving exercise, but this finding was not confirmed. It was noted that the small study size and differences between the placebo and iron-treated patient groups at the start of the study may have impacted the results. Side effects were similar between the two groups.

Sharlene giving a talk at a renal event
Dr Sharlene Greenwood presenting at UK Kidney Week

Dr Sharlene Greenwood commented; “There may be a role for treating low iron levels in people living with kidney disease, even without the presence of anaemia. Although further research is needed, there is a signal in our work that by treating reduced iron levels, we may be able to support improvements in exercise capacity in patients living with CKD.”

Dr Aisling McMahon, director of research and policy at Kidney Research UK added, "We’d like to thank Sharlene and the researchers involved in Iron and Muscle for their ongoing work to support the kidney disease community, and we look forward to further results. Kidney Research UK are committed to accelerating discoveries for the kidney patient community by supporting all types of scientific studies, and I would encourage researchers to look at how our grant programme might enable their future research too."

This study was funded by a grant from Kidney Research UK, which was supported by an unrestricted grant from Vifor Fresenius Medical Care Renal Pharma.

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