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A study of haemodialysis patients partly funded by Kidney Research UK, has found dialysis can cause short term problems with cognitive function. Everyone’s brain function decreases over time but after one year on dialysis, patients were at a slightly increased risk of worsening memory.

However, the research showed patients who had a transplant and were able to stop dialysis had an improvement in memory and verbal learning brain functions. Researchers believe identifying those most at risk may help to limit side-effects.

For patients with kidney failure, dialysis is a lifesaving treatment. While cognitive impairment is commonly seen in this patient group, until now scientists did not know exactly why this occurred. Researchers now believe reduced blood flow to the brain during dialysis may be the cause.

“Dialysis is a lifeline for people with end stage kidney disease,” said Sandra Currie, chief executive of Kidney Research UK.“We helped to fund this study as we want to make life on dialysis as positive and healthy as possible. With these findings we have a better chance of progressing research to make sure we can minimise any detrimental impact of dialysis.”

Scientists at the University of Glasgow looked at almost 100 patients using hemodialysis over a 12-month period. They measured cerebral blood flow, tested each patient’s cognitive function during and after dialysis and used MRI scanning to assess any white matter changes to patients’ brains.

The researchers found blood flow to the brain was reduced during dialysis and patients’ cognitive function decreased as well. Those who remained on dialysis were more at risk of memory loss due to reduced blood flow during the procedure.

Professor Patrick Mark, Professor of Nephrology at the University of Glasgow, said: “This is an important study which we believe supports the current hypothesis that dialysis is associated with cognitive impairment. Crucially we found that while patients both on short and long-term dialysis treatment had some form of cognitive impairment, patients who went on to receive a transplant saw an improvement in their white matter and in their memory.”

Cognitive impairment is very common in patients treated with hemodialysis, with up to 70% found to have it. Some patients describe the feeling of being in a ‘dialysis fog’ during treatment. The frequency of cerebrovascular disease is also 10 times more common in patients with end stage kidney disease than those in the general population.

Dr Mark Findlay, from the University’s Institute of Cardiovascular and Medical Sciences, said: “Based on our findings it would appear that early recognition of those patients most at risk may help to limit this potential side effect, which may be reversible by kidney transplant.”

The paper, ‘Investigating the relationship between cerebral blood flow and cognitive function in haemodialysis patients’ is published in the Journal American Society of Nephrology. The work was funded by Kidney Research UK, the Stroke Association and Darlinda’s Charity for Renal Research.